Robertson, K. M., Newton, R. U., Doan, B. K., Rogers, R. A., Shim, J., Popper, E. M., Horn, B., Hakkinen, K., Kraemer, W. J. (2001). Effects of in-season strength and power training on squat jump performance in NCAA women volleyball players. Medicine and Science in Sports and Exercise, 33(5), Supplement abstract 764.

The effects of four weeks of in-season strength and power training on the ability to rapidly develop force during jumping were evaluated in 12 Division I female volleyball players. Testing occurred before and after a traditional strength and power training experience. The dependent variable was force created by the concentric portion of a squat jump. Normal training and competitions occurred during the training period.

Time to peak force decreased, peak force increased, and average concentric force increased. There was no change in the rate of force development, a component of improved speed. Athletes were stronger as a result of the experience while "speed" of force development did not change.

Since no control group was used in this study, one is set to ponder whether the strength gains were "retraining gains", because the study implies that no strength training had occurred in-season. If pre-season strength training was experienced and then stopped, resulting in strength-detraining, it is possible the observed changes in this investigation were re-adaptations and possibly unrelated to performance. If strength gains from pre-season training were appropriate for volleyball, their use in training and competitions should have stimulated them to be maintained and additional strength training would have resulted in little to no further gains.

Implication. Additional in-season strength training improves existing strength in females if they are not undergoing concurrent strength training. The question as to whether the strength gains transfer to improved performance was not answered.

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