ERFORMANCE
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SOCCER
CONDITIONING
A NEWSLETTER DEDICATED TO IMPROVING SOCCER PLAYERS
www.performancecondition.com/soccer
Training - Higher May NOT Be Better
Gary Rothbart
Gary Rothbart is the Canadian Director of the Tudor Bompa Institute. He is certified by the
Tudor Bompa Institute as a Strength and Conditioning Specialist, Periodization Planning Specialist,
Conditioning Specialist for Ice Hockey and Junior Athletic Training Specialist. He is a Level 2 TPI
Certified Golf Fitness Instructor and is certified by the American Council on Exercise.
BEG
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lyometric training is a form of power training. It is defined by the Webster's dictionary
as "exercise involving repeated rapid stretching and contraction of muscles (as by jumping and rebounding) to increase muscle power". The most common forms of plyometric
exercises involve the lower body but both lower body and upper body exercises can be
performed.
As mentioned in Webster's definition, the goal of plyometric training is to increase muscle
power. This can be accomplished by increasing the speed of muscle contractions by moving the time
curve to the left. Moving the time curve to the left refers to the speed of muscle contractions. The ability
to do so is dependent upon the type of training techniques being performed. As an example, if the athlete's goal is to increase size (muscle hypertrophy) slower resistance training that induces high levels
of fatigue is required. This type of training will move the time curve to the right as the time that it takes
Gary Rothbart
to perform a muscle contraction will increase to 250 milliseconds or greater.
There are many types of plyometric training techniques that are currently being used to train elite athletes. When designing
a plyometric training program, consideration must be given to the biomotor abilities of the sport. The goaltending position in soccer
involves repeated jumping/instant change of direction movements throughout the competition. Therefore, plyometric training should
be a major component of the training program. The purpose of this article will be to examine the physiological effects of plyometric
training and its relationship to improved performance for elite soccer goaltenders.
The goal of power training is to decrease the time needed to perform a muscle contraction. When performing plyometric exercises the goal should be to lessen the amount of time the athlete spends on the ground. This is known as the amortization phase.
Ideally, the time would be less than 200 milliseconds. On average, ground contact times of the plant/takeoff foot in jumping events
range from 100 milliseconds to less than 200 milliseconds.
Another determining factor for improved performance is intensity. For many years, exercises such as loaded jump squats,
depth jumps from higher heights, single leg jumps and single leg bounding exercises have been associated with greater intensity
levels. A recent study on plyometric training contradicts this theory. The study compared EMG activity for 10 commonly used plyometric training exercises. One test measured EMG activity in athletes performing unloaded double leg jumps and compared these
results to loaded jumps with the industry standard load of 30% of 1RM placed across the athletes shoulders. The other test compared
depth jumps from a 30cm height (approximately one foot) and depth jumps from a 61cm height (approximately two feet). The group
performing the study were surprised to find that EMG activity was LOWER in the loaded jump group and in the group performing
depth jumps from the 61cm height. The natural inclination would be to assume that more intense activities would yield greater intensity levels. In this instance, the opposite is true. The reason for a reduction in intensity can be attributed to the golgi tendon organ.
The golgi tendon organ is a proprioceptive sensory receptor and is a protective mechanism that is designed to protect the body. When
jumping from heights that are in excess of one's potential, the golgi tendon organ sends a signal to the central nervous system slowing
the rate of descent at a rate of 50-100 milliseconds resulting in less force being applied upon landing. As a result, many of the plyometric training exercises currently being performed by elite athletes are inhibiting performance. "Studies by Bosco and Komi (1979)
demonstrate that jump performance increases with increasing stretch loads applied. For example, during drop jumping, the height of
the subsequent jump increases with increases in drop height. This occurs only up to a point. There is a threshold at which the stretch
load is too great and the golgi tendon organ reflex causes an inhibition of muscle contraction reducing the jump height attained (Goll-
hofer @ Kyrolainen, 1991; Schmidtbleicher et al., 1988)".
Another popular form of plyometric training involves single leg exercises such as jumps and bounding. For many years the
assumption has been that this form of training produces greater levels of intensity compared to double leg jumping exercises. This
does not appear to be the case. The study mentioned earlier in this article compared EMG activity with participants performing
double leg jumps and single leg jumps. The results show that double leg jumps induce higher EMG response and are considered to
be higher intensity exercises. In addition, single leg jumps will lead to increases in the amortization phase and impact the athlete's
ability to increase power.
Now that we have an understanding of intensity levels and the amortization phase, let's look at the physiology. Plyometrics
are based on the theory that a pre-stretched muscle contracts more forcefully. This is known as the stretch-shortening cycle. The progression is as follows; the participant performs an eccentric contraction also known as the stretch portion of the movement, performed
as a downward movement of the lower body or semi-squat, followed by an involuntary isometric contraction. The third phase of the
movement is the jumping portion or takeoff and is referred to as the concentric phase or shortening phase. The force is applied in
both directions with the force being slightly higher during the concentric phase.
There are numerous types of plyometric exercises currently being used by elite athletes. These include but are not limited to
the following; skipping, stepping, two-foot vertical jumps, tuck jumps, single leg hops, cone jumps, single leg and double leg bounding
exercises, drop jumps, box jumps, low reactive jumps and shock tension. The types of exercises, number of sets, repetitions per set,
training sessions per week, age of the athlete and experience performing these types of exercises should be considered when designing
the program.
It is important that the training program does not induce high levels of fatigue. The coach should reduce the number of repetitions per set and or discontinue the set if the athlete is showing signs of fatigue. Increases in the amortization phase are a sign that
the athlete is in a state of fatigue. Verbal communication can also be used to identify levels of fatigue.
Adequate rest intervals between sets are a priority and longer rest periods of up to 10 minutes between sets may be necessary
following intense bouts of activity.
References: Periodization Training For Sports Second Edition, Human Kinetics, Bompa T.O. PhD, Carrera M.C., 2005.
Evaluation of Plyometric Intensity Using Electromyography, Journal of Strength and Conditioning Research; 22(3)/861-868, Ebben
W.P., Simenz C., Jensen R.L., 2008.
What is the most direct means to achieve strength gains specific to the demands of jumping events? Kerin, D.
More Information Please! contact Gary Rothbart [email protected].