Time-course Of Changes In Maximal Force And Rate Of Force Development After A Plyometric Training Session

Abstract

Plyometric exercise causes reductions in muscular performance that may persist for several days. However, there may be differences in the magnitude and the duration of changes in maximal force and muscle power. PURPOSE: To evaluate the effects of a single session of plyometric training on the time-course of changes in maximal force and rate of force development (RFD) measured during maximal isometric and dynamic exercise METHODS: Seven moderately trained university students (4 males and 3 females, age: 20.0±0.7 yrs, height: 174±3 cm, body mass: 70±5 kg) performed a plyometric training session consisting of 3 sets of 10 repetitions of 7 jumping exercises: drop, scissor, box, stride crossover and depth jumps and steps and single leg hops on the track (total volume: 210 jumps), with 1 min recovery between sets and 3 min between exercises. Maximal isometric leg press strength and RFD (knee angle set at 90o) and countermovement jump (CMJ) height and RFD were measured using a force platform, before, 30 min after and 24, 48, 72, and 144 h after the plyometric training session. Data were analyzed using one-way ANOVA with repeated measures and Tukey’s post-hoc test. RESULTS: Maximal isometric force was decreased by 26±9% (from 3541±456 to 2436±256 N, p<0.05) only 30 min post-training and returned to baseline after 24 h. However, RFD during isometric exercise was decreased to a greater extent 30 min after (-38±9%, p<0.01), remained lower than baseline 24 h later (-16±8%, p<0.05) and returned to baseline 48 h after training. The reduction in CMJ height was larger 48 h after training (-7.2±2.5 %, p<0.05) and remained below baseline for 72 h after training (-5.2±2.5 %, p<0.05). RFD during the CMJ exhibited a decrease that was larger 48 h after training (-30±9 %, p<0.01) and persisted until the 72 h time-point. CONCLUSION: These data show that a single training session with a high volume of plyometric jumping exercises reduces maximal isometric force only temporarily, while the decrease in RFD is larger and persisting, especially during dynamic muscle contractions.