The aim of this study was to investigate changes in vertical jump technique over the course of a training session. Twelve plyometric and ballistic exercise trained male athletes (age = 23.4 ± 4.6 years, body mass = 78.7 ± 18.8 5 kg, height = 177.1 ± 9.0 cm) performed three sets of 10 repetitions of drop (DJ), rebound (RJ) and squat jumps (SJ). Each exercise was analysed from touch down to peak joint flexion and peak joint flexion to take-off. SJ were analysed from peak joint flexion to take-off only. Jump height, flexion and extension time and range of motion, and instantaneous angles of the ankle, knee and hip joints were measured. Separate one-way repeated ANOVAs compared vertical jump technique across exercise sets and repetitions. Exercise set analysis found SJ had lower results than DJ and RJ for the angle at peak joint flexion for the hip, knee and ankle joints and take-off angle of the hip joint. Exercise repetition analysis found the ankle joint had variable differences for the angle at take-off, flexion and extension time for RJ. The knee joint had variable differences for flexion time for DJ and angle at take-off and touch down for RJ. There was no difference in jump height. Variation in measured parameters across repetitions highlights variable technique across plyometric and ballistic exercises. This did not affect jump performance, but likely maintained jump performance by overcoming constrains (e.g. level of rate coding).
Chandler, P., Greig, M., Comfort, P., & McMahon, J. J. (2018). Variability of plyometric and ballistic exercise technique maintains jump performance. Journal of Strength and Conditioning Research, 32(6), 1571-1582. https://doi.org/10.1519/JSC.0000000000002572