How To Raise a Successful Athlete is a great text for the ‘layman’
interested in expanding his or her knowledge of basic sport-related topics.
It is easy to comprehend the information regarding nutrition, physiology,
biomechanics, strength training, sport psychology, as well as coaching
and medical topics. The book describes the common occurrences of injury,
appropriate treatments and home care information so the parent or guardian
recognizes the importance of proper therapeutic remedies.
The chapters are well organized and clearly labeled for quick reference
and the information is presented in a straightforward and understandable
manner. Each chapter highlights helpful tips or bulleted information.
Specific issues are highlighted that should be of concern to the parent
or guardian.
Recommendation: This book is a good foundational reference for those
with no experience or background in exercise physiology, sport nutrition,
and/or sport-related topics. It is an introductory source for parents
or guardians seeking a better understanding of the topics and issues athletes
face in sport participation.
How to Raise A Successful Athlete: What you need to know to raise a successful athlete
By: Thomas Craig Angle
Trafford Publishing
ISBN: 1-41206372-8
Accurate kinematic analysis of human movement is a significant factor for the improvement of movement performance and for the reduction of injuries. A polynomial method for 3-D analysis was implemented to determine the knee kinematic parameters during level and 9% downhill grade running. The knee kinematic parameters for the level and downhill running were: 20.9 o and 17 o degrees for the flexion angle in foot strike, 36.2 o and 43.1 o for the peak flexion angle in stance phase, and 7.1 rad.sec -1 and 7.4 rad.sec -1 the peak flexion angular velocity respectively. The knee kinematic characteristics, determined using a polynomial method, were within the range of the respective values reported in previous studies, indicating that the polynomial method used is adequate for accurate 3-D kinematic analysis. The results indicate that the knee extensor muscle group is worked over a greater range during downhill running than in level running and furthermore, during the footstrike, the knee flexion angle, in level running is higher than in downhill running, which probably could be affected to the magnitude of the compression forces applied to knee during downhill running.
INTRODUCTION
The biomechanical aspects of running are significant factors for the identification of optimal running mechanics in order to improve the athlete’s performance and to identify the mechanical strategies that can be applied to reduce mechanical overloading of the locomotor system and thus prevent injuries (Nigg, 1985; Subotnick, 1985; Brown and Yavorsky, 1987; Armstrong, 1990; Gross and Napoli, 1993, Herrington, L. 2000 ). The stance phase of gait (walking and running) is a closed chain lower extremity activity that requires coordinated movement between the proximal and distal joints. The lower limb performs many essential dynamic functions ( Ross et al . , 2 004) ., during the stance phase, that enable the body to be propelled forward during gait. In running, as the velocity increases (compared with waking) and the stance phase decreases, there is a double unsupported phase or flight phase and the double support limb phase vanishes (Enoka, 1988). This seems to reflect to the higher proportion of eccentric and concentric muscle work performed in running (specifically, during downhill running). The kinematics and kinetics of the ankle have been extensively documented in previous studies (Kaelin et al., 1985; McKenzie et al., 1985; Soutas-Little et al., 1987; Nigg and Morlock, 1987; Engsberg and Andrews, 1987; Nigg et al., 1988; Kepple et al., 1990). Although the contribution of the knee angle in human locomotion is important and the knee is susceptible to injuries (over 25% of all running injuries reported by Hamill et al. (1992)), there are few previous studies in this field (i.e. Andriacchi, 1990). Cipriani et al. (1995) was determined the kinematic parameters of hip, knee and ankle and evaluated the muscle adaptations in the gait cycle produced by walking backward on a treadmill at 0, 5, and 10 percent inclination. This is a common tool for lower extremity rehabilitation in the clinical setting. There are a few studies investigating the different kinematic characteristics of the knee angle, in order to identify the causes of muscle damage during level and downhill running (Hamill et al., 1984; Buczek and Cavanagh, 1990). Kinematic adaptations during downhill, uphill and level running were measured by Hamill et al. (1984), using a high speed cine camera. In this study, the reported values for the knee flexion angles at heal strike were 15.27 o and 20.06 o degrees for 9% gradient downhill and level running respectively. Similar values for knee flexion angles were reported by Buczec and Cavanagh (1990), using a similar gradient (8.3%).
The main purpose of this study was to apply a polynomial method (Pigos and Baltzopoulos, 1993) for the measurement of knee joint kinematics during
level and downhill running.
METHOD
Instrumentation
A motorized treadmill (Woodway), capable of operating at different speeds and gradients, was used. Treadmills have been frequently used for kinematic analysis in previous studies (Soutas-Little et al., 1987; Nigg and Morlock, 1987; Hamill et al., 1984; Buczek and Cavanagh, 1990; Hamill et al., 1992; Iversen and McMahon, 1992) and there is no significant difference to overground running, when the speed is less than 5 m.s -1 (Williams, 1985; Williams et al., 1991). The speed of the treadmill belt (length 3.6 m) was approximately 3 m .s -1 for both the level and downhill running. The selection of this speed was based on speeds used in previous studies (Hamill et al., 1984; Buczek and Cavanagh, 1990; Iversen and McMahon, 1992; van Woensel and Cavanagh, 1992) and was used to facilitate the comparison of the results. During downhill running, the treadmill was elevated up using an iron structure, in order to provide a gradient of 9% similar to those used by Hamill et. al (1984) and Buczek and Cavanagh (1990) (Fig. 1).
A calibration procedure was performed before both run protocols, using a calibration plane with dimensions 2.1 m wide X 1.1 m high formed by aluminum square tubes (Fig 2). Forty seven markers were mounted on the square tubes throughout the calibration plane. The position of every marker was precisely measured from the lower left marker (origin) of the calibration plane (measurement error 0.5 mm). Four additional square tubes (0.5 m length) were positioned perpendicularly on the calibration plane. The edge points of the square tubes were used to determine the 3-D camera position (camera determination points).
The calibration plane was formed by a prefabricated structure using aluminum square tubes. Forty-seven markers were mounted on the square tubes throughout the calibration plane, but only t hirty calibration points was used for this study . The position of every marker was precisely measured from the lower left marker (origin) of the calibration plane (measurement error £ 0.5 mm). Two additional square tubes (0.5 m length) were positioned perpendicularly on the calibration plane (Fig 2). The edge points of these square tubes were used to determine the 3-D camera position (camera determination points).
The calibration plane was placed between the camera positions and the athlete, so that the athlete was within the calibrated volume throughout the level and downhill running (Fig. 3).
Figure 3. The experimental set up for the level and downhill running.
The calibration plane and subsequently the athlete’s movements were recorded using two S-VHS Panasonic F-15 cameras fitted with WV-LZ14/15E lenses. Once the calibration plane was recorded it was then removed and no additional calibration procedure was performed between the level and downhill running. The cameras were mounted on tripods with no panning possibility and were positioned as illustrated in figure 3.
The angle between the two camera optical axes was approximately 90 0. The synchronization of the shutter in both cameras was achieved using a gen-lock system (WV-AD 36E Panasonic gen-lock adaptor). The speed of the shutters was fixed at 1/500 sec in order to eliminate any blurring and improve image quality.
Two S-VHS Panasonic AG-7330-B video recorders recorded the movement with a frequency of 50 field of view per frame. The same S-VHS recorder, an Intel 82386 based-computer and a developed coded Pascal (version 6) based on the algorithm described by Pigos and Baltzopoulos (1993) (see below in “ Polynomial method and digitizing procedure”), were used to review and analyze the recorded data.
Subject
One 21 year old female runner (height 1.73 m and body mass 65 Kg), performed the level and downhill running. Explanation of the experimental procedure was given and anthropometric measures (body mass and height) of the subject were taken before running. Skin markers were not attached to the subject. This was based on the results of a previous study by Ronsky and Nigg (1991), who concluded that relative movement can occur between markers attached to the skin, if the base for the marker is not rigid. Moreover, because of relative movement between the skin and the bone, the markers attached to the skin may not precisely describe the movement of the underlying bone and consequently the marker cannot represent accurately the center of rotation of the joint, which must be digitized, throughout the entire movement.
The subject was allowed to familiarize herself with the treadmill and warm up for 2 min before the level and 1 min before the downhill running. Once the subject had achieved the test speed (approximately 3 m.s -1) 30 seconds of the level and downhill running was recorded.
Polynomial method and digitizing procedure
The determination of the 3-D coordinates of the athlete was estimated using the polynomial procedure (Pigos and Baltzopoulos, 1993). The 3-D coordinates of any point are determined as the intersection of the lines formed by the positions of (at least) two cameras and the projections of the point on the calibration plane from the two camera views. The formulation of a first degree polynomial model consists of the following equations:
X p = a 1+a 2x+a 3y (1)
Y p = b 1+b 2x+b 3y (2)
where X p, Y p are the coordinates of the projection of any digitized point on the calibration plane mapped from the 2-dimensional x, y camera image coordinates.
Consequently, three or more calibration points with known X, Y coordinates are required, in order to evaluate the polynomial coefficients a 1..a 3 and b 1..b 3 using the first degree polynomial. Thirty calibration points and two camera determination points (see fig 3) were used, for the estimation of the coordinates of the digitized points. This procedure was performed for each camera. Once the calibration points were digitized (in the video reference system) and stored, the polynomial coefficients in equations (1) and (2) were determined using the closest calibration points of every digitized point. Two complete cycles, one from level and one from downhill running, were digitized. In addition, ten frames before the first footstrike and ten after the last toe-off of the gait cycle, were also digitized to provide a buffer for filtering (Fig 4).
In the analysis procedure, only the kinematic characteristics of the left knee in the stance phase were extensively analyzed, although the entire body was reconstructed. This analysis of the knee was performed to facilitate comparison of the results, using the polynomial method described in Chapter 3, with other published studies (Hamill et al., 1984; Buczek and Cavanagh, 1990; Williams et al., 1991; Hamill, 1992; Iversen and McMahon, 1992; van Woensel and Cavanagh, 1992).
Data analysis – Smoothing procedure
Before the estimation of the kinematic parameters, a filtering procedure was applied to smooth the data and minimize the signal noise (Miller and Nelson 1976; Winter, 1979; Wood, 1982). Different smoothing methods have been reported and implemented in previous studies for the reduction of noise from the raw displacement data (Reinsch, 1967; Reinsch, 1971; Zernicke et al., 1976; McLaughlin et al., 1977; Pezzack et al., 1977; Hatze, 1981; Lanshammar, 1982; Vaughan, 1982; Niinomi et al., 1983; Garhammer and Whiting, 1989). Digital filters are frequently used in kinematic analysis achieving effective reduction of the noise. More specifically, Pezzack et al. (1977) compared angular acceleration signals from an accelerometer with those obtained from synchronized film and concluded that the digital filters reduced effectively the signal noise, reflecting the accurate estimation of the kinematic parameters. Vaughan (1982) assessed the displacement data of a falling ball, using cine cameras and different smoothing methods: Cubic spline, quintic spline and digital filter. In this study the results indicated that although the quintic spline was superior to the other methods, digital filters could produce accurate results. Garhammer and Whiting (1989) compared the five-point moving arc, spline and digital filter methods and concluded that there was no significant difference in the estimation of kinematic parameters, using the above smoothing methods.
The use of digital filters in running applications
Williams and Cavanagh (1983), in a study for the calculation of mechanical power during distance running, used digital filtering with a cutoff frequency of 5 Hz to smooth the 3-D coordinates. Winter (1983) used a digital filter with a cutoff frequency of 8 Hz to smooth the 2-D raw data obtained during running. A digital filter with a cutoff frequency of 7.5 Hz was also used by Buczec and Cavanagh (1990) to filter the digitized data collected from the level and downhill running. Hamill et al. (1992) in the study for the determination of the relationship between the subtalar and knee joint actions, during the support phase of level treadmill running, used digital filters with cutoff frequencies ranging from 8 Hz to 18 Hz. Digital filters and an arbitrary cutoff frequency of 12 Hz were used by Woensal and Cavanagh (1992), to smooth the 3-D reconstructed coordinate of running subjects, using optoelectronics cameras. It is evident that the application of low pass digital filters (Butterworth filters) is an adequate smoothing method for kinematic analysis, extensively implemented in previous running studies. However, the selection of the optimum cutoff frequency remains a significant factor for accurate measurements (Winter, 1979). Winter (1974) reported that for the knee angle (in walking) there are no significant harmonics higher than the 6th (6 Hz). Williams (1993) highlighted that digital filtering frequencies for running kinematic data are typically in the range of 2 to 10 Hz (when a 100 Hz sampling rate is used).
Smoothing procedure
In this study digital filters were used to smooth the raw data. The format of the second order Butterworth digital filter used is the following:
F i = a 0R i + a 1R i-1 + a 2R i-2 + b 1F i-1 + b 2F i-2
where a 0, a 1, a 2 and b 1, b 2 are the filter coefficients which are constant and determined by the ratio of the sampling frequency to cutoff frequency, R i and F i the raw and the filtered data respectively. The algebraic sum of the filter coefficients must be 1 in order to give a response of unity over the pass band. The filtering of data for the second time, but in the reverse direction of time, results in the creation of a fourth-order, zero phase shift filter.
The digital filter was coded in the developed Pascal program and tested using the raw data reported in a previous study (Vaughan, 1982). The criterion for the efficacy of the coded smoothing method was the accurate estimation of the second derivative (acceleration), where the error due to signal noise is high. The cutoff frequency (6 Hz) was that recommended by Vaughan (1982). The second derivative (acceleration) of the movement, with respect to time, was calculated using the mathematical expressions proposed by Miller and Nelson (1976). Forward, central and backward difference formulae were implemented for second derivative of displacement (raw) data using two points on either side of the point to be smoothed:
where: X i the acceleration at point x i.
the point x i+1 : the x coordinate of the point one frame before
x i+2 : the x coordinate of the point two frames before
x i-1 : the x coordinate of the point one frame after
x i-2 : the x coordinate of the point two frames after
The results (Fig. 5) indicate that the digital filter is an adequate smoothing method for kinematic data and consequently implemented in the present study.
Figure 5. Determination of a falling ball’s acceleration (Vaughan 1982), using digital filter.
The optimal cutoff frequency of the filter was determined by filtering the data using different cutoff frequencies until the difference between the variance in the raw and the filtered data was minimal (Pezzack et al., 1977). The selected optimal cutoff frequency was 4 Hz.
Kinematic parameters
The angles between the segments were calculated using simple geometric expressions consisting of the direction vectors of the two lines formed by (at least) three non collinear points (Bowyer and Woodwark, 1983)):
(4)
where f 1, f 2, g 1, g 2 are the directions of the two lines formed by (at least) three non collinear points (see Chapter 5) and the angle between the two lines.
The first angular derivative (angular velocity) was calculated using the formulae proposed by Miller and Nelson (1976). The mathematical expressions for the forward, central and backward formulae of angular velocity, using two points on either side of the point to be smoothed, are:
where: X i the angular velocity of the x i point.
the point x i+1 : the angle one frame before
x i+2 : the angle two frames before
x i-1 : the angle one frame after
x i-2 : the angle two frames after
Figure 6 illustrates the conventions used for the knee angles and angular velocities ( ω ).
RESULTS
In order to facilitate comparisons, the values of the angles in the stance phase
are expressed in degrees, whereas the angular velocities are expressed in rad.sec -1 according to the format of the results in the study by Buczek and Cavanagh (1990). The flexion knee angle (stance phase) in the foot strike (FA) was 20.9 o degrees for the level running and 17.4 o for the downhill running (Table 1). The peak knee flexion angle during the stance phase (PFA) was 36.2 o and 43.1 o for the level and downhill running respectively. The time of the peak flexion (TPFA), expressed as a percentage of the total time of the stance phase, was 35.7 % and 50.0 %. The peak flexion angular velocity (PFAV) was 7.1 rad.s -1 and 7.4 rad.s -1 for the level and downhill running respectively. The time of the peak angular velocity (TPFAV) was 14.2 % and 21.4 % of stance phase for the level and downhill running respectively. The knee angle throughout the stance phase is illustrated in figure 7. The difference between the flexion angle during foot strike and the peak flexion angle (ROM) was 15.3 o and 25 o for the level and downhill running respectively.
Level Running
Downhill running
Flexion angle in foot strike (degrees)
20.9 o
17.4 o
Peak flexion angle (degrees)
36.2 o
43.1 o
Time of the peak flexion angle (percentage of total stance phase)
35.7 %
50 %
Peak flexion angular velocity (rad.s -1)
7.1
7.4
Time of the peak angular velocity
14.2 %
21.4 %
Difference between the flexion angle during foot strike and the peak flexion angle (degrees)
15.3 o
25 o
Table 1. Summary of kinematic analysis during stance phase
Figure 7. The knee angle throughout the stance phase .
Reliability
Although the reliability of the polynomial method implemented in the reconstruction of 3-D coordinates has been examined (Pigos and Baltzopoulos, 1993) using spatial coordinates, a different reliability analysis using angular measurements (FA in footstrike) was also performed. In this examining procedure, ten repeated digitization of a single frame (footstrike) from every camera view were used when the subject performed level running. The low value of the standard deviation (0.89 o) and the coefficient of variation (4.40%) of the angular measurements, indicate that the polynomial method is reliable for the 3-D body segment reconstruction (Fig 8).
DISCUSSION
In this study the knee kinematic parameters during level and downhill running were calculated using the reconstructed 3-D coordinate of the runner joints applying the polynomial method described in Chapter 3. Two and three dimensional studies have examined lower extremity kinematic adaption during level and downhill running. Newham et al. (1988) concluded that the knee extensor muscle group is worked over a greater range during downhill running than in level running. The kinematic analysis of the knee in level and downhill running in previous studies highlighted that FA in level running is higher than in downhill running, with a difference ranging from 3.3 o to 7.6 o (Hamill et al., 1984; Buczek and Cavanagh, 1990). Hamill et al (1984) reported a direct relationship between knee angle at footstrike and the gradient in downhill running. Buczek and Cavanagh (1990) demonstrated that the PFA is higher in downhill running with a difference of 4 o from level running. The PFAV is higher overall, according to previous studies in downhill running, and the difference ranged from 0.6 rad.s -1 to 2.3 rad.s -1 (Hamill et al., 1984; Buczek and Cavanagh, 1990).
The results of the present study indicate that the values of the kinematic parameters determined using the polynomial method, were within the range of the respective values reported in previous studies.
More specifically, the FA at footstrike in level running was similar with the FA of 20.08 o reported by Hamill et al. (1984), higher than 11.2 o reported by Hamill et al. (1991) and lower than 24.6 o reported by Buczek and Cavanagh (1990), whereas the FA in downhill running in the present study was higher than Hamill et al. (1984) (15.3 o) and similar to Buczek and Cavanagh (17.0 o). Based on the results of the present study and previous (Hamill et al. 1984) regarding the higher flexion angle estimated in level running is than in downhill running, could probably be affected to the magnitude of the compression forces applied to knee during downhill running and it one of the issue should be considered from the trainers.
The PFA for level running was similar with the respective values of 35.4 o reported by van Woensel and Cavanagh (1992), but lower than those reported by Buczek and Cavanagh (1990), Williams et al. (1991), Hamill et al. (1991), and Hamill et al. (1992) (43.9 o, 44.5 o, 43.8 and 44.1 o respectively). The PFA for the downhill running was lower than Buczek and Cavanagh (47.9 o). The PFAV was similar with the respective values reported by Hamill et al. (1992), but less than those of Hamill et al. (1984), Buczek and Cavanagh (1990), Williams et al. (1991). The difference between the FA and the PFA (ROM) was similar with the respective ROM in the Buczek and Cavanagh (1990) study. The difference between the FA and the PFA, indicates that the knee extensor muscle group is worked over a greater range during downhill running than in level running and should be considered from the trainers.
A summary of measurement values of left knee kinematic parameters and comparison with other published studies (Hamill et al., 1984; Buczek and Cavanagh, 1990; Williams et al., 1991; Hamill et al., 1991; Hamill et al., 1992; van Woensel and Cavanagh, 1992) are presented in Table 7.1. Motorized treadmills have been used in previous studies.
The variability of kinematic parameters reported in different studies can not provide a criterion for the accurate estimation of the methods. However, the above comparison of the kinematic parameters was considered sufficient to estimate the validity of the polynomial method implemented.
The difference between the kinematic parameters reported in different studies, is due to the variability in the individual running style (Williams, 1993) and body mass between the subjects used (McKenzie et al., 1985), kinematic asymmetries of lower limbs (Holden et al., 1985; Vagenas and Hoshizaki, 1992), different recording (type of cameras and set up) and analysis procedures (two or three dimensional analysis, filtering, cutoff frequency, differentiating expressions and algebraically manipulation of the data).
Table 7.1.Summary of knee joint kinematic during stance phase of the present and previous studies. (1: Hamill et al., 1984, 2: Buczek and Cavanagh, 1990, 3: Williams et al., 1991, 4: Hamill et al., 1991, 5: Hamill et al., 1992, 6: van Woensel and Cavanagh, 1992.)
Studies
grad%
speed m.s -1
FA degrees (±SD)
PFA (±SD) degrees
TPFA % stance (±SD)
PFAV rad.s -1 (±SD)
TPFAV % stance (±SD)
ROM FA-PFA
Present study
0
3
20.9
36.2
32.1
7.1
14.2
15.3
– 9
3
17.4
43.1
50.0
7.4
21.4
25.7
1
0
3.8
20.1
–
–
10.1
–
–
– 9
3.8
15.3
–
–
12.4
–
–
2
0
4.5
24.6 (3.0)
43.9 (3.6)
33.6 (2.4)
7.97 (1.2)
4.3 (1.9)
19.3
– 8.3
4.5
17.0 (4.2)
47.9 (3.3)
40.7 (1.9)
8.57 (0.38)
15.0 (0.0)
30.9
3
0
5.5
–
44.5
–
–
–
–
–
–
–
–
–
–
–
–
4
0
2.9
11.2 (6.9)
43.8 (5.1)
184 (55) *
–
–
32.6
–
–
–
–
–
–
–
–
5
0
**
–
43.4
44.7
7.1
21.5
–
–
–
–
–
–
–
–
–
6
0
3.8
–
35.4 (4.1)
90.0 (7.1) *
7.82 (1.46)
30.6 (6.4) *
–
–
–
–
–
–
–
–
* The time in these studies was reported in milliseconds and not as % of stance phase. For comparison purposes, the TPFA of the present study was 70 ms for the level and 120 ms for downhill running. The TPFAV was 30 ms and 40 ms respectively.
** The running speed of this study has not been reported.
The results of Cipriani et al. (1995) were not included, because referred to walking procedure and not to running.
In previous studies there is no specification of the analyzed lower limb (left or right). Furthermore, the gradient in downhill running is also reflected in the variability of the kinematic parameters between the studies. The coded developed program for the kinematic analysis of the movement enables the facility for rotation of the movement and view of the image in three different pairs of axes: X – Y, Y – Z and X – Z, with varying interval times between the frames. Thus, a better observation of the image movement can be accomplished. It is important to note that the design of the recording procedure (cameras view point and set up) has not focused in the knee joint, as has been reported in previous studies. Thus, the polynomial method presented is accurate and adequate for the kinematic parameters estimation of any body segment and consequently for the 3-D analysis of the movements.
CONCLUSION
A polynomial method was applied in the 3-D kinematic analysis of the level and downhill running. The comparison of the results, in knee kinematics with previous studies, indicates that the polynomial method is an adequate method for the analysis of the movement. The simplicity and the efficiency of the method in the calibration procedure, compared with previous calibrated methods and the accuracy in the determination of spatial points and angles, render the method suitable for 3-D analysis of movement.
The results indicate that the knee extensor muscle group is worked over a greater range during downhill running than in level running and furthermore, during the foot strike, t he knee flexion angle, in level running is higher than in downhill running, which probably could be affected to the magnitude of the compression forces applied to knee during downhill running
Dr. George Pigos is a graduate of the Physical Education and Sports Science department of the University of Athens, Greece with a specialization in swimming trtaining. He holds a Ph. D in Biomechanics/Kinisiology from the University of Liverpool in England. He is a research assistant at the University of Athens and has worked as a lecturer for seven years at Northumbira University in Newcastle, England. He is a member of the Board of Directors of the International “Sport for All” Federation and was the director of sector timeing, scoring and results for the Athens Organizing Committee for the 2004 Summer Olympic Games.
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Submitted by: Bert H. Jacobson, Jennifer Kaloupek & Doug B. Smith
ABSTRACT
Purpose
To compare the use of standard, anati-shock, and no hiking poles on medio-lateral (Fx), anaterio-posterior (Fy) and vertical (Fz) ground reaction forces for the foot and hiking poles while during load carriage walking at 0% grade. Methods: Subjects were solicited from experienced backpackers who had used hiking poles for at least 5 years. Each subject was fitted with an 18 kg internal frame backpack and allowed to practice walking with and without hiking poles to a metronome cadence equal to a walking speed of 4.42 Km.hr-1. During each successful trial the subjects contacted a piezoelectric force plate positioned in the floor with the foot and contralateral hiking pole. Three trials were conducted in random order 1) without hiking poles (NP), 2) with standard (SP) hiking poles, and 3) with anti-shock (AP) hiking poles. For each trial the following data were recorded: 1) Medio-lateral (FFx), anterior-posterior (FFx), and vertical (FFz) ground reaction force for the foot medio-lateral (PFx), anterior-posterior (PFx), and vertical (PFx) pole forces.
Results
No significant differences in foot reaction forces were found among the three conditions (NP, SP, and AP) for any of the recorded dimensions (medio-lateral, anterior-posterior, and vertical). Also, no significant differences in force parameters was evident between the two types of hiking poles.
Conclusion
No significant weight transfer from lower to upper body was evident regardless of pole design indicating that dependency on hiking poles during load carriage walking on level ground is negligible.
The use of hiking or trekking poles has become popular with both the weekend recreational hiker as well as the serious hiker. As early as 1996, 49% of hikers in the Austrian and Italian Alps were using “trekking poles” (Rogers et al, 1995). Over the last few years, hiking poles have evolved from simple, single walking sticks to dual, spring-loaded, telescopic poles equipped with wrist straps and carbide tips. Manufacturers of hiking poles have made largely unsupported and anecdotal claims of the benefits of employing hiking poles while hiking. Such claims as extra balance, surer walking, and reduction of stress are common (Jacobson et al, 2000). The claim supporting “reduction of stress” on lower limbs (Haid and Koller, 1995; Wilson et al, 2001) stems from the belief that part of the load is transferred from the legs to the arms and shoulders Neurether, 1981).
Previous studies involving hiking poles have included mixed protocols. For instance, some hiking poles with such names as Exerstriders® and Power PolesT are marketed for the purpose of increasing fitness parameters and caloric expenditure rather than for hiking activity by suggesting exaggerated arm swing. In a study using Power PolesT, Porcari and associates (1997) measured selected physiological variables during a 20 minute treadmill test at self selected speed and grade and found significant increases in oxygen consumption (VO2), respiratory exchange, caloric expenditure, and heart rate. In another study Rodgers and associates8 found that using Exerstriders® while walking for 30 minutes, at 6.7 km.hr-1 on 0% grade with exaggerated arm swing significantly increased VO2, and HR by 12% and 9% respectively.
However, in two separate studies utilizing hiking poles in a traditional hiking manner and without excessive arm motion, both groups of researchers found no significant differences in oxygen consumption between pole and no pole use during a 1 hr, 5% inclined treadmill walk with a 22.4 kg backpack (Knight and Caldwell, 2000) or during a 15 min. inclined (10%-25%) treadmill walk while carrying a 15 kg back pack (Jacobson et al, 2000). Also Jacobson and associates (2000) found no differences in minute ventilation (VE) or caloric consumption (Kcal.min-1 ) between pole and no pole conditions. Some authors have found greater heart rate (Neurether 1981; Procari et al, 1997; Sklar et al, 2003) with pole use, while others have reported no significant differences in heart rate between pole and no pole use (Jacobson and Wright, 1998; Jacobson et al, 2000). It has been suggested that discrepancies in results may be due to the variations in research protocols among the studies.
While there is general agreement that hiking poles do not reduce energy utilization and may, if used in an exaggerated manner, increase energy utilization as illustrated by caloric consumption, ventilation, and heart rate. With respect to rating of perceived exertion (RPE), the predominance of literature (Jacobson and Wright, 1998; Jacobson et al, 2000; Knight and Caldwell, 2000) suggest that walking with hiking poles provide an impression of reduced exertion when compared to not using hiking poles. It is possible that the perception of reduced exertion when using hiking poles results from an increase in stability provided by the additional points of contact (Neurether, 1981). Jacobson and associates (1997) found that stability and balance was significantly improved with the use of both one and two hiking poles.
Early claims that hiking poles reduces the overall stress on the limbs by transferring the weight to the arms and ultimately to the poles (Haid and Koller, 1995; Unione Internazionale, 1994) were largely unsupported until recently. Schwameder et al (1999) examined external and internal loads on the knee joint during declined (25%) walking with and without hiking poles and found significant differences in peak and average magnitudes of ground reaction forces, knee joint movement, an dtibiofemoral compressive and shear forces with pole use. Wilson and associates (2001) found a decrease in average vertical ground reaction force (Fz) while using walking poles at self-selected speeds. This decrease in vertical ground reaction force was evident for two separate poling conditions when compared to using no poles.
The purpose of this study was to compare differences in load bearing, three dimensional foot and hiking pole ground reaction force between standard, anti-shock or no hiking poles while during 0% grade walking.
Methods
Subjects
Twelve healthy males (mean age = 35.3, SD + 10.3yr.; mean mass = 81.6, SD + 5.4 kg; mean height = 177.8, SD + 12.6 cm) with a minimum of 5 years of hiking and hiking pole experience volunteered to participate in the study. Only those subjects known as active and current hikers/mountaineers were solicited for the study and all were briefed on the protocol and signed an informed consent document approved by the University IRB committee. These subjects had no history of orthopedic pathology of lower or upper extremities and were active year-around. Following, the oral briefing, subjects’ weights and heights were recorded and a medical history was obtained. No subject was unable to participate due to medical or physical constraints.
Procedure
Subjects were tested under three randomly assigned conditions: 1) without hiking poles (NP), 2) with two standard hiking poles (SP), and 3) with two anti-shock hiking poles (AP). Subjects were instructed to maintain an easy pace to replicate a typical long-term hike. A walking speed of approximately 5.0 Km·hr-1 as determined by photo-electric cells located immediately before and after the force plate was used to standardize the pace for each trial. The testing area consisted of an18 m runway with a piezioelectric force-plate positioned midway at ground level. Pre-test trials were conducted in order to assure consistent pace and contact with the force plate by the subjects’ foot and pole during testing. Subjects were instructed to walk so that pole plant coincided with contralateral heel strike (Wilson, et al. 2001).
Trials consisted of walking from each subject’s predetermined starting point and culminating by walking 3 meters beyond the force plate contact. Before testing, subjects were given ample opportunity to practice walking to the cadence along the runway in order to consistently and naturally contact the force plate.
Prior to each testing session a commercially made backpack, (Gregory Mountain Products, Inc.) including a load weighing 20 kg and consisting of an internal-frame and equipped with sternum strap, hip belt, and load lifters, was individually adjusted for each subject according to the manufacturer’s suggestions. Fitting the backpack involved shoulder strap adjustments to torso length, hip belt positioning, and sternum strap width and tightness. Two separate pairs of similarly weighted (~ 300 g) hiking poles, one standard pair (Cascade Designsâ Inc. Seattle, WA) and one pair with anti-shock capabilities (Leki-Sport USAâ Inc., Williamsville, NY) equipped with adjustable, telescopic sections and wrist straps, were individually fitted for each subject according to the manufacturer’s recommendations and previously conducted studies ( Jacobson and Wright, 1998; Jacobson et al. 2000; Wilson et al. 2001).
Instrumentation
A piezoelectric force plate (Kistler Instruments AG Winterthur, Schweis. 9287BA) interfaced with Bioware Analysis System Tym 2812A1-3 computer software capable of recording medio-lateral (Fx), anterior/posterior (Fy) and vertical (Fz) forces on contact was situated midway in the runway, level with the ground, and covered by a rubber mat extending the length of the runway. For each trial the following peak force data were recorded:
Foot Ground Reaction Force – Medio-lateral (FFx), anterior-posterior (FFy),
and vertical (FFz).
Pole Ground Reaction Force- Medio-lateral (PFx), anterior-posterior (PFy),
and vertical (PFz).
Following backpack/hiking pole fittings and practice sessions, subjects were randomly assigned to one of the three conditions (NP, SP, AP). Three successful trials were recorded for each condition for a total of nine trials. Data for each trial was spot-checked to assure consistency among results.
Statistical Analysis
Repeated measures of analysis for variance techniques were used to compare differences in medio-lateral, anterior-posterior, and vertical ground forces among the three conditions. Significant pair-wise differences were determined by the Newman-Keuls post-hoc test. An alpha level of P< 0.05 was required for statistical significance.
Results
The repeated measures analysis of variance analysis of foot ground force reaction among the three groups (NP, SP, AP) for the three dimensions (medio-lateral [FFx], anterior-posterior [FFy]and vertical [FFz]) yielded significant differences (Table 1) within the three dimensions, but no significant differences between groups (p= 0.87) and no significant interaction effect (p=0.95). Simply stated, these results indicate no modification in foot ground reactions forces for any of the pole conditions (NP, SP, or AP). Analysis of pole ground reaction force yielded significant differences (Table 2) within the three dimensions, but no significant group (SP and AP) difference (p=0.56) and no significant interaction effect (pp=0.65). These results provide no evidence that one pole design is more beneficial than the other in the transfer of ground reaction force from the foot to the pole.
Table 1
ANOVA for Foot Ground Reaction Force by Group (NP, SP, AP) and Dimension (FFx, FFy, FFz).
Source
df
MS
F
p
Within Group
2
15.2
.130
0.874
Between Group
2
315395.8
5077.044
0.000
Interaction Effect
4
10.8
.173
0.951
Table 2
ANOVA for Pole Ground Reaction Force by Group (SP, AP) and Dimension (PFx, PFy, FPz).
Source
df
MS
F
p
Within Group
1
41.49
.341
.561
Between Group
2
8404.83
105.91
0.000
Interaction Effect
2
36.12
.455
.635
Conclusions
No significant differences in foot ground reaction forces were found among the three conditions (no poles, standard poles, and anti-shock poles) for medio-lateral (Fx), anterior-posterior (Fy), or vertical (Fz) dimensions. Also, no significant force differences were found between the use of standard poles and anti-shock poles while walking on flat ground. A previous study (Schwameder et al., 1999) involving down-hill walking found significantly less peak and average magnitudes of ground reaction force was produced when walking with hiking poles in comparison to not using hiking poles. The authors concluded that the reduction of ground reaction force was primarily due to the forces applied to the hiking poles in a breaking action. Another study involving uphill walking (Knight and Caldwell, 2000) concluded that hiking pole use reduced activity in several lower extremity muscles thereby reducing stress from lower extremities. These authors also suggested that such stress reduction was because of the transfer of propulsion force from the lower to the upper extremity.
In a study using level ground walking at self-selected speeds, Wilson and associates (2001) found that “walking” poles produced significantly faster walking, greater stride length and stance time, along with an average 2.9% reduction in vertical ground reaction forces. In comparison, the current study produced smaller ground reaction force (FFz) means with the employment of either of the two hiking pole designs while walking 4.42 Km·hr-1 at 0% grade. The current study yielded a decrease in foot reaction force (FFz) of .91% for the standard poles and 1.21% while using the anti-shock poles (Figure 1). The anti-shock poles (AP) group recorded 12% greater vertical ground reaction force (PFz) when compared to the standard poles (Figure 2).
In contrast to the current study, Wilson and associates sampled novice subjects and instructed them to utilize the hiking poles in two distinct manners: 1) plant pole to coincide with contralateral foot strike, 2) same pole/foot plant with pole angled backward at ground contact, and 3) same pole/foot plant with pole angled forward at pole plant (Wilson et al, 2001). The subjects for the current study were not given special instructions on pole use, rather, subjects employed the poles with the technique they had previously developed through their outdoor hiking experiences. It appears by these data that experienced hikers depend minimally on hiking poles while walking on flat gournd, in that no significant transfer of force between upper and lower extremities was evident. In contrast to up-hill and down-hill walking which requires increased propulsion (Knight and Caldwell, 200) and breaking force (Schwameder et al, 1999) respectively, 0% grade seems to require no additional dependency on hiking poles, specifically through the transfer of force away from the lower to the upper extremities.
It is plausible that the ground reaction variables measured in the current study were compromised by the short duration of testing. In contrast to actual hiking, the average testing duration for the current study involved a practice period and thee successfully completed trials, which lasted a total of betwenn15 and 20 minutes. In normal hiking situations, the duration of walking is extended by several hours and as fatigue becomes a factor, the reliance on the hiking poles is likely to become greater in order to reduce the demand on the lower extremities. Further, greater dependency on hiking poles may become evident as the terrain changes from flat to incline, decline or lateral slant. Recommendations for future studies should encompass longer walking durations, inclined/declined walking, and lateral slant in order to more closely resemble actual hiking activity.
ACKNOWLEDGEMENT
Equipment furnished by Gregory Mountain Products, Inc., Cascade Designsâ Inc. Seattle, WA., Leki-Sport USAâ Inc., Williamsville, NY
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8. Porcari J, Hendrickson T, Walter R, Terry L, Walsko G. The physiological responses to walking with and without Power PolesT on treadmill exercise. Res Q Exerc Sports 1997;68: 161-166.
9. Roeggla M, Wagner A, Moser B, Roeggla G. Hiking sticks in mountaineering. Wild Environ Med 1996; 3: 258.
10. Schwameder H, Roithner R, Müller E, Niessen W, Raschner C. Knee joint forces during downhill walking with hiking poles. J Sports Sciences 1999; 17(12): 969-978.
11. Sklar J, DeVoe D, Gothall, R. Metabolic effects of using bilateral trekking poles whilst hiking. 2003; 44: 173-185.
12. Unione Internazionale delle Associazoni Alpinistiche Medical Commission Official Standards of the. Hiking poles in mountaineering, vol. 3. Swiss Medical Commission of UIAA, 1994.
13. Wilson J, Torry MR, Decker MJ, Kernozek T, Steadman JR. Effects of walking poles on lower extremity gait mechanics. Med Sci Sports Exerc 2001, 33(1): 142-147.
The purpose of this study was to examine the effects of the speed function on some technical elements (dribbling, slalom and agility) in soccer, and to determine the effect ratio of these elements on one another. Some information regarding the purpose of this research is given by means of literature review. The subjects of the study, 177 soccer players selected from the 1st, 2nd, and 3rd League, amateur and two youth teams in Ankara, Turkey, has undergone a performance test including one each of a sprint 0-15-30 m, slalom 0-15-30 m, and dribbling 0-15-30 m, and an agility test. Sprint, slalom and dribbling tests were applied twice, with the players resting between each trial. Finally, the agility test was performed. The reliabilities of the tests (Sprint = .74; Slalom = .61; Dribbling = .76; Agility = .81) were determined for the players (n=40). The performance values of the subjects examined showed that while speed function does affect the agility competency, it had no effect on slalom and dribbling competency. The other findings showed that slalom and dribbling competencies affect each other positively.
Introduction
In soccer, in addition to mental, psychological, physiological and coordinational features, the improvement of conditional features is important as well. Peak conditional features in soccer players provide an advantage. Much of what affects the results of a match occurs during or after the high intensity sprint. Analysis of the specific movements and activities performed by football players during games can provide much relevant information on which suitable training programs can be designed (Dawson, 2003).
Success in soccer is dependent upon a variety of factors including the physical characteristics and physiological capacities of the players, their level of skill, their degree of motivation, and tactics employed by them against the opposition. Some of these factors are not easily measured objectively, but others can be tested using standardized methods and can provide useful information for coaches (Mosher, 1985).
In soccer, speed plays an important role; the accelerated pace of the game calls for rapid execution of typical movements by every member in a team. In many instances, successful implementation of certain technical or tactical maneuvers by different team members is directly related with the degree of velocity deployed (Kollath & Quade, 1991).
According to the Dawson study (2003), the large majority of sprints performed in soccer take six seconds or less to complete, over distances of only 10-30 meters, and many of the sprints involve at least one change of direction.
As running speed increases, longer strides are taken. In this instance, the swing phase involves greater knee flexion and hip extension, and greater hip flexion in the latter part of the phase (Howe, 1996).
During soccer games, many actions affect the result of games. These actions are characterized by intermittent and multi-directional movements, as well as the movements of changing intensity and time.
Reilly and Ball (1984) stated that each game typically involves about 1000 changes of activity by each individual in the course of play, and each change requires abrupt acceleration or deceleration of the body or an alteration in the direction of motion.
Specific physical and physiological characteristics of soccer players can be used by coaches to modify training programs and to help players prepare for the game strategy. The modern soccer relies on the ability of all players to attack and defend whenever necessary. Therefore, it is important that all players achieve a high level of performance in the basic skills of kicking, passing, trapping, dribbling, tackling and heading. Analysis of the physical and physiological characteristics of the players and determination of the specific requirements for optimal performance are thus a necessity (Tiryaki et al., 1996).
Technique refers to the relationship and harmony a player demonstrates with the ball and describes the performance of a solitary action in isolation from the game, e.g. pass or dribbling (Bate, 1996).
Dribbling a ball was chosen in this study as this represents one of the most exciting aspects of the game for spectators, and a great deal of time is devoted in training to its practice (Reilly & Thomas, 1979).
When running with a ball, much shorter strides are taken as the player must be ready to change direction and speed. At the toe-off phase, the leg may not be as extended heel stride may not be as pronounced, rather the foot may land in a more neutral position or be plantarflexed (Howe, 1996).
It is known that players with sprint skills have advantage over other players. However, the degree of effect has not been determined. In this study, we wanted to determine the degree of effect of sprint on technical elements. In other words, the purpose of this study was to examine the effects of the speed function on some technical elements in soccer, and to determine the effect ratio of these elements on one another. Thus, soccer-training programs could specify and propose the degree, frequency, intensity and volume of sprint and technical elements.
Methodology
Participants
This investigation was performed during the 1999-2000 season and included players from different league group teams competing in Ankara, Turkey (177 soccer players selected from 1st, 2nd, 3rd League, amateur and two youth teams). All subjects were informed about the purpose of the study and of its voluntary nature, and all provided their consent to participate. The study involved analyses of performance of these players. We examined the literature for related investigations.
Apparatus and Task
To establish reliability, the tests were applied to 40 players in ‘on season’ and ‘off season’. Paired sample t – test statistical tests were used. The reliability values were determined as follows:
According to match analysis, in match situation maximum sprint distance is approximately 20 – 30 m. However, the soccer players run about 100 sprints in the match (Kelly et al., 1982).
The subjects ran 30 m to measure their sprint performance. Crossing values (15 m and 30 m) were recorded by photocell (sprint 0 – 15; = .67 ; sprint 0 – 30; =.74).
The subjects ran between nine slalom sticks located 1.5 m apart. With photocell, 15 m and 30 m crossing values were recorded. Slalom – dribbling tests established by Kunts were applied (1991). Van Rossum practiced the test over 15 m, and reliability was determined as approximately .51. In this investigation, we determined reliability for slalom 0 -15 m as = .53; and for slalom 0 -30 m as = .61. The subjects dribbled the ball between the nine slalom sticks located 1.5 apart. With photocell, 15 m and 30 m crossing values were recorded, and reliability for dribbling 0 -15 m was determined as = .68; and for dribbling 0 -30 m, = .76.
“Agility refers to the capability to change the direction of the body abruptly. The ability to turn quickly, dodge and sidestep calls for good motor coordination and is reflected in a standardized agility run test.” (Reilly, 1996). Agility tests comprise different directional movements with changes between 35 m and 142 m in area (Haywood, 1986). Wilmore (1992) has defined agility as the ability to change movement direction, and it constitutes conjunction of sprint, strength, stability and coordination factors.
The agility test used was that developed by Lindquist and Bangsbo (1994), and its formation and dimension included the football penalty area. The reliability was found as .81 (n=20). We conformed to the elements of this agility test, in which the athletes ran as fast as possible through the tests with this sequence: sprint (40 m), back sprint (8.25 m), sprint (8.25 m), sprint (8 m), slalom (70 m), sprint (8 m), side sprint (8.25 m), side sprint – opposite direction (8.25 m).
Testing Procedure
The tests included one each sprint 0-15-30 m, slalom 0-15-30 m, and dribbling 0-15-30 m, followed by the agility test. Sprint, slalom and dribbling tests were applied twice, with the players resting between trials. Finally, the agility test was performed. Descriptive statistics of the subjects are presented in Table 1.
Data Analysis
The acquired data was transferred to the computer and evaluated with SPSS (Statistical Package for Social Sciences). The descriptive statistics (f, %) and Pearson Moments Multiple Correlation and Paired sample t-test statistical tests were used. Significance level was determined at .05.
Results
All participants completed the test procedure. Results attained from the subjects were classified according to the mean, standard deviation, minimum, maximum and range, and are presented in Table 2.
Correlations between sprint, slalom, and dribbling were tested with bi-variate Pearson Moments Multiple Correlation, and results are given in Table 3. As can be seen, statistically significant positive (p.05) correlation was determined between the following: agility and sprint 15; agility and sprint 30; dribbling 15 and dribbling 30; slalom 15 and slalom 30; sprint 15 and sprint 30; dribbling 15 and slalom 15; dribbling 30 and slalom 15; dribbling 30 and slalom 30; and dribbling 15 and slalom 30.
Apart from the above, other relation among the variables was statistically insignificant. No statistically significant relation was determined between sprint and dribbling and slalom values, but there was a positive correlation between slalom and dribbling.
Discussion
We determined participants’ mean age as 23.72 3.4 years, mean height 179 6.5 cm, mean weight 72.4 6.7 kg, and mean training years as 8.5 3.4 years. In this study 0-15 m sprint value was approximately 2.25 sec, 15-30 m 1.85 sec and 0-30 m 4.14 sec. Winkler (1991) reported 0-15 m sprint value as approximately 2.43 sec, 15-30 m as 1.71 sec, and 0-30 m as 4.14 sec. These findings support our study.
In subjects with good sprint values, agility values were significantly more meaningful (r = .49) (P < .05). Although according to Balsom (1994), soccer players who have good sprint ability cannot also be skilled in agility. In this study, players having good sprint values also had significantly more meaningful agility values. Similar results were also found in the study done by Herm (1993). He found that there was a correlation between 30 m sprint value and agility (r =.65), and this data support our findings.
According to the Little & Williams study (2003), there is a significant correlation between maximum speed and agility ( r = 0.34 p< 0.05). There is a notion that maximum speed and agility are distinctly specific attributes. The specificity may be attributable to differences in the musculature utilized strength qualities required and complexity or of motor control, between the different speed components.
To find the relationships between dribbling and slalom, one study was conducted by Van Rossum and Wijbenga (1991). According to the statistical analysis, correlation value was found (r=.59). In this investigation, a statistically meaningful relationship (r=.55) was determined between dribbling and slalom. High perception skills are needed in slalom and dribbling skills; however, perception does not affect sprint and agility skills. The participants who did well in the slalom test also performed well in dribbling tests. This high correlation between slalom and dribbling can be explained by the similarity among step frequencies, movement and dynamic changes, and specific and compulsive concentration.
No significantly meaningful relation was found between sprint and dribbling and slalom values. According to the definitions of sprint and dribbling elements (Howe, 1996), it is seen that while the anatomical movements resemble each other, angle and velocity of the extremities differ. We assume this is why speed had no affect on dribbling.
According to the study, it is seen that performance of acyclic speed and dribbling are affected by performance of cyclic speed run. In soccer, the importance of cyclic running has decelerated because of changes in the structure of play. Because action is limited to a narrow field, acyclic speed and dribbling can be more important in taking opponents out of play and gaining an advantage. It is suggested that speed drills should be formatted with both acyclic and different dribbling, which more directly supports the necessary qualities of modern soccer.
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Appendices
Table 1. Height, Weight and Training Years of the Football Players
Variable ( n = 177 )Height (cm)Weight (kg)Training (year)
Mean (sec.)1.7972.48.55
SD (sec.).066.753.40
Min. (sec.)1.6560.01.0
Max. (sec.)1.9892.020.0
Range (sec.).3332.019.0
Table 2. Agility, Sprint, Slalom and Dribbling Results,
Variables ( n = 177 )AgilitySprint 0-15Sprint 15-30
Submitted by: Don Melrose Ph.D. CSCS & Ronald G. Knowlton Ph.D. FACSM
ABSTRACT
The purpose of this investigation was to examine the effects of a hybrid, simultaneous, resistance and aerobic training program on aerobic power and muscular strength. Free-weight 1RM elbow flexor strength and cycle ergometer maximal aerobic power (CE VO2 max) were assessed for 15 untrained subjects. All tests were performed prior to and following a six-week training program. Subjects were randomly assigned to three training groups: an aerobic-training group, a strength-training group, and a simultaneous-training group. All training was performed three times per week. Aerobic training consisted of five to six, three-minute bouts of high-intensity exercise performed on a calibrated Monark cycle ergometer. All training intervals occurred at 85 to 100% of the subject’s CE VO2 max. Training intervals were separated by three minutes of rest. Strength training consisted of performing arm-flexion exercise with the subject’s dominant arm using a free-weight dumbbell. The strength training protocol consisted of performing four working sets of exercise per session separated by three minutes of rest. The first two weeks of training consisted of four sets of 10RM, the third week at 8RM, the fourth at 6RM, the fifth at 4RM, and the sixth at 2RM. The simultaneous training group performed both the aerobic and strength training protocols simultaneously. The aerobic and simultaneous groups significantly (p< 0.05) increased aerobic power 33.6 ± 6.1 to 39.1 ± 6.8 and 36.2 ± 3.7 to 42.3 ± 5.4 ml×kg-1×min-1 respectively. There was no significant difference in aerobic power increase between the aerobic and simultaneous training groups. The strength and simultaneous training groups significantly (p < 0.05) increased 1RM strength 11.36 ± 3.2 to 16.81 ± 5.1 kg and 13.81 ± 5.13 to 17.72 ± 6.15 kg respectively. There was no significant strength difference between the strength and simultaneous training groups. In conclusion, simultaneous high-intensity, cycle ergometer, aerobic training and one-arm, free-weight, strength training can be effectively utilized to increase maximal aerobic power and dynamic elbow-flexor strength. This study shows that the concept of simultaneous, high-intensity, aerobic and strength training is viable and that this approach to training may perhaps become a conditioning option for athletes and non-athletes.
INTRODUCTION
Strength and endurance training serve as the cornerstone of both athletic training and basic fitness regimens. A seemingly endless variety of modes, methods, and techniques are routinely utilized to achieve greater performance and fitness. At the forefront of these training methods is concurrent training. Concurrent training generally refers to the performance of both aerobic and anaerobic exercise within a fitness or athletic training program. To that end, strength and endurance training are applied in varying sequences within the same workout, daily, or weekly schedule. Athletes as well as popular and commercial fitness applications capitalize on these basic themes and supply the consumer with unlimited exercise options. Included within this variety are techniques which combine both resistance and aerobic training at the same moment in time, not separately. Such techniques are now very popular and are most commonly utilized in group-exercise settings in which individuals utilize barbells or dumbbells with the upper body and some kind of aerobic movement with the lower body at the same moment in time. For clarity, this type of training will be referred to as simultaneous training.
Currently, available research does not document simultaneous training as defined above. However, numerous studies have investigated the interactions of strength and aerobic training on muscular strength and aerobic power resulting from traditional same day or different day simultaneous training. These investigations often report mixed results (Abernethy & Quigley, 1993; Dudley & Djamil, (1985), Gravelle & Blessing, 2000; Hennessy & Watson, 1994; Hickson, 1980; Hunter, Demment, and Miller, 1987, McCarthy, Pozniak, and Agre, 2002; McCarthy, Agre, Graf, Pozniak, and Vailas, 1995). In all reviewed investigations, experimental training groups that performed concurrent training had no impairment in the magnitude of aerobic power increase as compared to those training groups that performed aerobic training only. The numerous physiological and structural adaptations resulting from aerobic training appear to be unaffected when combined concurrently with strength training. Some studies in which concurrent training was performed showed significantly less increase in muscular strength as compared to those experimental groups that performed strength training only (Dudley & Djamil, 1985; Hennessy & Watson, 1994; Hickson, 1980). Then again there are a number of studies which show little, if any, impairment in the magnitude of strength gain (Abernethy & Quigley, 1993; Hunter et al. 1987, McCarthy et al., 2002; McCarthy et al, 1995, Volpe, Walberg-Rankin, Webb-Rodman, and Sebolt, 1993). Most investigations reporting strength decrement report that strength gain decrement is isolated to the same muscle group that was utilized during the aerobic training portion of the study. Currently there is a lack of consensus among investigators as to the exact cause(s) of strength gain impairment as a result of concurrent training
Regardless of the degree of compatibility concurrent training may afford to increases in muscular strength and aerobic capacity, each of the aforementioned studies utilizes unique training methodologies and experimental designs. These key differences make it difficult to discern the degree of effectiveness and optimal application of concurrent training. Simultaneous training further complicates training and training outcomes due to its hybrid nature. This type of training is physically complicated and requires full body coordination. Since it does not involve a separation of the two modes of training and is relatively difficult to effectively coordinate, the efficacy of this training is unclear in either laboratory or group-exercise settings. The objective of this experiment was to examine the efficacy of synchronizing strength and endurance training and its effect on muscular strength and aerobic power.
METHODS
Subjects
Fifteen subjects, nine women and six men, ranging in age from 18 to 28, were recruited for this study (Table 1). Prior to data collection, subjects had not participated in a regular exercise program for a period of six months. All subjects were required to fill out a medical history questionnaire for the purpose of screening for contraindications to participation. The Southern Illinois University at Carbondale Human Subjects Committee granted approval for this study. Subjects were informed of the risks associated with participation in the study and subsequently signed an informed consent prior to data collection.
Table 1. Subject characteristics (mean ±SD )
Variable
Women (n = 9)
Men (n = 6)
Age (y)
21.1 ± 2.6
21.2 ± 1.5
Height (cm)
158.5 ± 16.6
180 ± 6.7
Weight (kg)
69.8 ± 7.7
88.0 ± 20.7
Body Fat (%)
26.1 ± 5.2
15.2 ± 5.5
Experimental Design
Subjects were assigned to one of three training groups. Each training group was randomly assigned three women and two men. The first training group was a strength-training group (STG) only, the second was an aerobic-training group (ATG) only, and the third was a simultaneous-training group (SNTG). All subject testing occurred one week pre- and one week post-training. Subjects in all three training groups performed both strength and aerobic testing. All training was conducted three times per week at regular intervals, typically on an alternating daily basis. The duration of the training period was six weeks. All pre-testing took place within one week prior to and following the training period.
1RM Testing
A one repetition maximum (1RM) elbow flexion (bicep curl) test was performed unilaterally using the subject’s dominant arm. A plate loaded dumbbell was utilized for 1RM testing. Subjects were seated with their feet on the floor. Bicep curling was performed with the hand in the supinated position throughout the lift’s range of motion. A 1RM protocol consistent with NSCA guidelines was utilized prior to maximal testing (Baechle & Earle, 2000). A maximal lift was determined when the subject could complete only one repetition in strict form.
Aerobic Power Testing
A calibrated Monark cycle ergometer (Varberg, Sweden) was utilized for all aerobic power testing. Maximal cycle ergometer oxygen consumption (CE VO2max) was measured using a Parvo Medics, True Max 2400 Metabolic Measuring system (Concentius Technology). Subjects wore a Polar heart rate monitor during all testing. A five-minute submaximal warm-up period preceded commencement of the aerobic power testing protocol. A pedaling rate of 60 rpm was maintained throughout the test. An initial work load of 60 Watts (W) was performed for one minute. At the beginning of each minute following the first minute, pedaling intensity was increased by 30 W. Heart rate was annotated at the end of each respective workload. Cycle ergometer VO2max was determined by the occurrence of one of the following; a plateau or decrease in oxygen consumption with a subsequent increase in workload, obtaining age predicted maximum heart rate or volitional fatigue. A brief cool-down period followed test termination.
Strength Training
Strength training was performed unilaterally with the subject’s dominant arm. A plate-loaded dumbbell was used to perform elbow flexion (bicep curl) exercise. As with the 1RM trial, strength training was performed in the seated position. The first and third training sessions of each week were designated “heavy” training days while the second was a “light” training day. Pilot testing revealed that muscular and joint soreness were an issue with three heavy training sessions per week. A brief warm-up period, consisting of two to three sets of 12-15 repetitions at about 50% of the subject’s 1RM, preceded each training session. Four working sets were performed during each training session following the warm-up period. The strength-training protocol was periodized by RM loads over the course of the six-week training program. The first two weeks of training consisted of performing arm flexion exercise at the subject’s 10RM load. The third week was performed at the subject’s 8RM load. The fourth was performed at the 6RM load, the fifth at 4RM, and the sixth at 2RM. Training loads were adjusted as needed throughout training sessions to achieve target repetitions across all sets. Light-day training sessions were performed at approximately 75 to 80% of the heavy training loads. All working sets were separated by three minutes of rest.
Aerobic Training
Aerobic training was performed on a Monark (Varberg, Sweden) cycle ergometer. Cycles were calibrated each week. A heart-rate monitor was worn by each subject during training to monitor exercise intensity during training. Following a brief warm-up period consisting of five to 10 minutes of light, sub-maximal pedaling, aerobic training commenced. Training sessions consisted of five, three-minute exercise intervals separated by three minutes of rest. All training intervals were performed at a pedaling rate of 60 rpm. Exercise bouts were performed at power outputs corresponding to the subject’s 85 to 100% CE VO2 max. Beginning the fourth week of training a sixth training interval at 85 to 100% VO2 max was added. Percentages of the subject’s CE VO2 max were calculated using the Karvonen method (American College of Sports Medicine [ACSM], 2000).
Simultaneous Training
Simultaneous training consisted of both the strength and aerobic training protocols performed at the same time. Upon initiating the aerobic training protocol and achieving the desired pedaling rate of 60 rpm, subjects were handed an appropriately loaded dumbbell. Subjects continued pedaling while curling the dumbbell until the desired repetition number for that set was achieved. Coordination of simultaneous exercise activities was achieved quickly by each subject. Upon completion of the set the dumbbell was removed and the subject completed the aerobic interval.
Statistical Analyses
All statistical analyses were performed using the SIUC mainframe Statistical Analysis Systems (SAS) program. Measures of central tendency and spread of data were represented as means and standard deviations. The experimental protocol employed a repeated measures design. A two by three repeated measures analysis of variance (ANOVA) was performed to analyze within and between group differences. Between- and within-group analyses consisted of the following for each group: 1) pre- and post- training 1RM and 2) pre- and post-training aerobic power measurements. The criterion alpha level was set at p < 0.05. All statistically significant interactions were analyzed to determine if either of the training groups had greater increases in either aerobic power or muscular strength from pre- to post-training than other training groups. Differential effects, a post-hoc technique, were utilized to analyze significant interactions between training groups (Khanna, 1994).
RESULTS
Muscular Strength
There was a significant increase in 1RM for the simultaneous training group from pre- to post-training (13.81 ± 5.13 to 17.72 ± 6.15 kg), an increase of 28.29%. There was a significant increase in 1RM for the strength training group from pre- to post-training (11.36 ± 3.20 to 16.81 ± 5.1 kg), an increase of 48.0% (Figure 1.). There was no significant difference in muscular strength increase between the simultaneous and strength training groups. The aerobic training group had no significant increases in muscular strength.
Figure 1. Changes in muscular strength pre-training to post-training.
Aerobic Power
The simultaneous training group significantly increased CE VO2max from pre- to post-training (36.2 ± 3.7 to 42.3 ± 5.4 ml · kg -1 · min-1), an increase of 16.75%. The aerobic training group significantly increased CE VO2max from pre- to post-training (33.5 ± 6.1 to 39.1 ± 6.8 ml · kg -1 · min-1), an increase of 16.49% (see Figure 2.). There was no significant difference in the magnitude of increase of the CE VO2max between the aerobic and simultaneous training groups. There was no significant increase in aerobic power for the strength training group.
Figure 2. Changes in aerobic power, pre-training to post-training.
DISCUSSION
In the present study, simultaneous training induced significant increases in both aerobic power and muscular strength. The independent strength and endurance training programs produced significant increases in both muscular strength and aerobic power respectively. Results indicate that hybrid simultaneous training, consisting of strength training and high-intensity aerobic training is capable of inducing significant increases in both muscular strength and aerobic power.
In simultaneous exercise, especially in group settings, the upper body is most benefited by resistance training since the lower body is performing the primary aerobic movement. Therefore, the greatest muscular strengthening occurs in the musculature of the upper body. Kraemer et al. (1995) referred to this effect as compartmentalization in which the upper body muscle groups are essentially unaffected by any negative effects of aerobic training. Group simultaneous exercise typically involves the use of relatively light barbells, dumbbells, or power bands. Training sessions persist up to an hour and include a variety of aerobic and resistance training movements. In the current study, utilizing lighter weights and a variety of movements was not practical. A primary goal of this study was to explore the efficacy of applying the two types of training so that the respective aerobic and resistance training stimuli occurred at the same time as in group settings. Given the results of the current investigation, it is reasonable to presume that group-style simultaneous training is a viable form of training.
Changes in aerobic capacity represent a durable adaptation in concurrent training. Superficially, it appears as if many physiological and structural adaptations that occur as a result of performing aerobic and strength training exercise may be antagonistic to each other. The specific adaptations common to endurance training include increases in capillary density, myoglobin, mitochondria, and oxygen uptake (Holloszy & Coyle, 1984). Aerobic training also has a tendency to decrease myofibrillar protein production in the muscle (Hoppeler, 1986). Strength training, however limits mitochondria, capillary supply, and production of aerobic enzymes (Luthi, Howald, Claassen, Vock, and Hoppeler, 1986; MacDougall, Sale, Moroz, Elder, Sutton, and Howald, 1979). According to Hurley, Seals, and Eshani (1984) while peripheral changes are important in the development of aerobic power, adaptations of the central circulatory mechanisms such as cardiac output and stroke volume are not affected by strength training. With respect to aerobic and strength training independently, this demonstrates that some physiological and structural adaptations to exercise have a more profound effect on the magnitude of the increase or decrease than others. The lack of significant difference in VO2max increases between the endurance and concurrent groups in several studies demonstrate that the development of aerobic capacity is independent of muscular strength increase (Dudley and Djamil, 1985; Hickson, 1980, Hunter et al. 1987; McCarthy et al. 2002; McCarthy et al., 1995; Volpe et al., 1993). The aerobic results of the current study were in agreement with those of the concurrent training studies.
Resistance training in its various forms elicits increases in muscular hypertrophy, increased stores of ATP and PCr, force generation, and anaerobic enzymes (Costill, Coyle, Fink, Lesmes, and Witzmann, 1979; Fleck & Kraemer, 1988; MacDougall, Sale, Elder, and Sutton, 1982; MacDougall et al., 1979). However, the greatest issue surrounding any type of simultaneous training regimen is strength gain inhibition. In some concurrent investigations in which the lower body was involved in strength and aerobic training, the lower body strength gains in the concurrent training groups were inhibited (Dudley & Djamil, 1985; Hennessy & Watson, 1994; Hickson, 1980). In Leveritt and Abernethy’s (1999) investigation, the ability of subjects to perform strength training was reduced following aerobic training. The strength inhibition experienced in the lower body demonstrates the susceptibility of the legs in general to strength gain impairment in response to concurrent training. Studies that performed resistance training with the upper body noted few if any problems with upper body strength increase when the legs were used to perform aerobic training. Kraemer et al. (1995) reported that effects of upper body strength training performed with endurance training seem to be generally compartmentalized to the upper body musculature, and did not significantly affect the force production or endurance capabilities of the lower body musculature. Interestingly, this does not appear to be the same relationship with aerobic and strength training performed by the arms. Abernethy and Quigley’s investigation (1993) noted no strength gain inhibition in a concurrent group that performed arm ergometry and isokinetic arm strength training. It was noted that further research will be needed to understand the different strength adaptation patterns in the quadriceps and triceps brachii respectively. The current study is in agreement with concurrent training study observations that show the upper body strength increases are not compromised by the aerobic activity performed by the lower body. Sale, MacDougall, Jacobs, and Garner (1990) noted; whether impairment, compatibility, or synergistic enhancement occur, the application of training volume, intensity, frequency, mode, training status of subjects decides the final outcome.
CONCLUSIONS
In the current investigation, aerobic and strength gain adaptations resulting from simultaneous training group were not negatively impacted. The adaptations of hybrid simultaneous training are much aligned with observations of traditional simultaneous training. While simultaneously achieved, muscular strength and aerobic power adaptations in the present study were likely not achieved due to the respective adaptations functioning in a complimentary capacity, but perhaps a compatible or even independent capacity. This training technique does pose limitations with respect to equipment, coordination, and number of exercises possible in combination. However, this type of training appears to be effective and may be used as a legitimate, but limited mode of exercise or conditioning. This type of training may also be used for off-season and pre-season conditioning for athletes as well. In conclusion, in untrained adults, simultaneous strength and aerobic training are as effective for increasing muscular strength and aerobic power.
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