Effects of a plyometric program on vertical landing force and jumping performance in college women

Objectives: To examine the effects of a plyometric program on peak vertical ground reaction force as well as kinetic jumping characteristics in recreationally athletic college women. Design: Six week prospective exercise intervention. Setting: Division I university campus. Participants: Twenty college females who competed recreationally in basketball were randomly assigned to a training (n=10) or control (n=10) group. Main outcome measures: The absolute change values for vertical ground reaction force, countermovement jump height, peak and average jump power, and peak jump velocity. Comparisons were made using Mann-Whitney U tests. Results: Vertical ground reaction force decreased in the intervention group (-222.8±610.9 N), but was not statistically different (p=0.122) compared to the change observed in the control group (54.6±257.6 N). There was no difference in the absolute change values between groups for countermovement jump height (1.0±2.8 cm vs. -0.2±1.5 cm, p=0.696) or any of the associated kinetic variables following the 6-week intervention. Conclusions: Although not statistically significant, the mean absolute reduction in vertical ground reaction force in the training group is clinically meaningful. Eight of the 10 women in the training group reduced vertical ground reaction force by 17-18%; however, improvements in jumping performance were not observed. This indicates that programs aimed at enhancing performance must be designed differently from those aimed at reducing landing forces in recreationally athletic women.