Influence of jumping strategy on kinetic and kinematic variables

Aim: Different jumping strategies can be used during plyometric training. Understanding how manipulating variables such as the counter-movement, flexion amplitude, the drop and the load could influence neuromuscular adaptation would be beneficial for coaches and athletes. The purpose of this study was to analyze how these variations in the vertical jump influenced kinematic and kinetic parameters as measured by a force platform.
Methods: Ten male subjects performed, eight kinds of vertical jumps on a force platform : (1) squat jump (SJ); (2) shallow counter-movement jump (S-CMJ); (3) natural counter-movement jump (N-CMJ); (4) deep counter-movement jump (D-CMJ); (5) loaded (20kg) counter-movement jump (20-CMJ); (6) shallow drop jump (S-DJ); (7) deep drop jump (D-DJ); (8) six consecutive jump test (6CJ). Customised Labview software was used to calculate time, displacement, velocity, acceleration, force, power, impulse and stiffness. After statistical analysis, jumping variables were grouped to achieve spécific training objectives.
Results: The mechanical parameters were largely influenced by the jump strategy, all the deep jumps produced superior jump heights and concentric velocities as compared to the shallow jumps. The exercises associated with greater power outputs were the S-DJ (5386±1095w) and 6CJ (5795±1365w) that involved short impulse durations and very high accelerations. The greatest values of muscle stiffness were not recorded during the highest vertical jumps, meaning that stiffness is not critical for jumping high.
Conclusion: This study gives an overview of what is changing when we manipulate jumping variables and instructions given to the athletes. Plyometric exercises should be carefully selected according to the sport and specific individual needs.