CHANGES IN STATURE FOLLOWING PLYOMETRIC DROP-JUMP AND PENDULUM EXERCISES

The aim of this study was to compare the changes in stature following the performance of plyometric exercises using drop-jumps and a pendulu m swing. Eight male participants aged 21.7+/-1.8 years with experience of plyometric training gave their informed consent to act as particip ants. :Participants undertook two exercise regimens and a 15-min stand ing test in a random order. The exercises entailed the performance of 50 drop-jumps from a height of 0.28 m or 50 pendulum rebounds. Partici pants were instructed to perform maximal jumps or rebounds using a 'bo unce' style. Measurements of stature were performed after a 20-min per iod of standing (pre-exercise), 2-min after exercise (post-exercise) a nd after a 20-min standing recovery (:recovery). Back pain and muscle soreness were assessed using an analogue-visual scale, at each of the above times and also 24 and 36 h after the test. Peak torque during is okinetic knee extension at 1.04 rads(-1) was measured immediately befo re and after the exercise bouts, to assess the degree of muscular fati gue. Ground/wall reaction force data were recorded using a Kistler for ce platform mounted in the floor for drop-jumps and vertically on the rebound wall for pendulum exercises. Drop-jumps resulted in the greate st (p < 0.05) change in stature (-2.71+/-0.8 mm), compared to pendulum exercises (-1.77+/-0.7 mm) and standing (-0.39+/-0.2 mm). Both exerci se regimens resulted in a significant (p<0.01) decrease in stature whe n compared to the standing condition. Drop-jumps resulted in significa ntly greater peak impact forces (p<0.05) than pendulum exercises (drop -jumps = 3.2+/-0.5 x body weight, pendulum = 2.6+/-0.5 x body weight). The two exercise conditions both invoked a small degree of muscle sor eness but there were no significant differences between conditions. Bo th exercise regimens resulted in a non-significant decrease in peak to rque indicating a similar degree of muscular fatigue. Based on the low er shrinkage resulted and lower peak forces, it can be concluded that pendulum exercises pose a lower injury potential to the lower back tha n drop-jumps performed from a height of 28 cm.