Newton, R. U., Kraemer, W. J., & Hakkinen, K. (1999). Effects of ballistic training on preseason preparation of elite volleyball players. Medicine and Science in Sports and Exercise, 31, 323-330.

Male NCAA volleyball players (N = 16) were pretested for vertical jump (standing and three-step) and a variety of aspects of vertical jumping (force, velocity, power production). Two groups were then formed. Each group participated in the team's volleyball practices and traditional strength training program. The treatment group participated in eight weeks of squat jump (ballistic) training while the control group completed squat and leg press exercises at 6 RM load. Thus, the independent variable was the type of squat contraction, ballistic or traditional heavy-isotonic. All Ss were retested after the training period.

Ballistic training consisted of six sets of six repetitions performed with two sets at each load of 30%, 60%, and 80% of each S's pretest 1 RM squat. An eccentric brake system removed close to 75% of the bar weight on the downward or eccentric phase of the squat.

The traditionally trained control group did not improve significantly on any of the measured variables. The ballistic group improved significantly more than the control group in standing and three-step vertical jumps. Overall force output increased, with increased rate of force development being the primary contributor to the vertical jump performance improvement.

Implication. Ballistic resistance training improves explosive performances such as vertical jump. Heavy resistance training does not improve explosive performance because it does not stimulate rapid force development.

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