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 specific 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±1095 W) and 6CJ (5795±1365 W) 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.

The ability of isoinertial assessment to monitor specific training effects.

AIM: The aim of this study was to investigate the ability of isoinertial assessment to monitor training effects. Both parametric and curve analysis of the results were used to underline the specificity of maximal strength and maximal velocity resistance training methods. METHODS: Twenty-four untrained subjects were randomly assigned into three groups: a maximal strength-training group (heavy loads: 80% to 98% of the one repetition maximum [1-RM]), a maximal velocity-training group (light loads: 25% to 50% of 1-RM) and a control group. All the subjects were tested in bench press exercises before and after the 6-week training period. An isoinertial dynamometer was used to assess velocity and power at four increasing loads: 35%, 50%, 70% and 95% of the 1-RM load. Post-test protocol also included a trial at 105% of the 1-RM load. RESULTS: Isoinertial assessment demonstrated for both training groups significant gains at each load. Some specific adaptations appeared: strength training presented a greater increase for average power (+49%, P<0.001) and average velocity (+48%, P<0.001) at 95% of 1-RM, while velocity training emerged as a more effective way to improve performance at 35% and 50% of 1-RM (+11 to 22%) in comparison with strength training (+7 to 12%). The analysis of power and velocity curves specified that strength training enhanced performance earlier in the movement, while velocity training extended the propulsive action at the end of movement. CONCLUSION: The original combination of parametric and curve isoinertial assessment appears to be a relevant method for monitoring specific training effects. The complementarity of both strength and velocity training programmes underlined in this study could lead to practical applications in profiling training programmes.

[Overtraining in endurance athletes]. / Surentraînement et efforts d'endurance.

Optimal training results in exercise-recovery harmonious balance. High frequency and volumic training, associated with insufficient recovery may induce overtraining. It depends on the kind of exercise but occurs mainly in endurance sports. The high frequency of upper respiratory track infection in endurance sportsmen results from a temporary immunosuppression state, possibly associated with overtraining. Many immune and haematological parameters have been associated with overtraining, but none seemed really efficient for diagnosis. Hormonal parameters, despite contradictions in studies, appear to give a good insight of athlete's staleness and are more predictive of overtraining. Actually, overtraining detection needs a combination of different parameters, and cannot sustain on isolated factors.