Coordination and power during Squat Jumps with loads controlled by an electromechanical dynamometer
The coordination between lower limb segments and power output developed during Squat Jumps in different load conditions was analyzed in ten trained male subjects (age 22.5±2.1 years; body height 176.5 ±5.4 cm; body mass 75.8 ±5.8; BMI 24.3± 1.8). We used a functional electromechanical dynamometer to control added load, 0% to 30% of body weight during the push-off phase. Significant differences between load conditions were evaluated by one-way repeated-measures ANOVA, p <0.05, for jump height, maximum vertical force, maximum vertical speed, and maximum angular speeds of the hip, knee and ankle. Pearson correlation coefficients were calculated to examine the relationships between jump height and the other variables. Angular velocities that presented significant differences between conditions were considered to analyze coordination through the graphs of the angular speed average values per condition during push-off phase. Power output decreased with the load and showed higher correlation with jump height at 30% load. This indicates that power training with SJ must be carried out without load, but to evaluate the power through the SJ height, a load of at least 30% should be used. Maximum articular velocities of hip and knee changed with increasing load and were correlated with height at 30% load. The final values and slope at the beginning of the push-off phase of relationship between hip and knee speed, indicate different coordination for 0% and load conditions and suggest a greater transfer from rotational to vertical speed in jumps without added load.