Article

In the present study we investigated displacement, time, velocity and
acceleration history of center of mass (COM) and electrical activity of knee
extensors to estimate the dominance of the factors influencing the vertical
velocity in squat jumps (SJs), countermovement jumps (CMJs) and drop jumps (DJs)
performed with small (40 degrees ) and large (80 degrees ) range of joint motion
(SROM and LROM). The maximum vertical velocity (v4) was 23.4% (CMJ) and 7.8% (DJ)
greater when the jumps were performed with LROM compared with SROM (p < 0.05).
These differences are considerably less than it could be expected from the
greater COM and knee angular displacement and duration of active state. This
small difference can be attributed to the greater deceleration during eccentric
phase (CMJ:32.1%, DJ:91.5%) in SROM than that in LROM. v4 was greater for SJ in
LROM than for SJ in SROM indicating the significance of the longer active state
and greater activation level (p < 0.001). The difference in v4 was greater
between SJ and CMJ in SROM (38.6%) than in LROM (9.0%), suggesting that elastic
energy storage and re-use can be a dominant factor in the enhancement of vertical
velocity of CMJ and DJ compared with SJ performed with SROM.
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Langue : ANGLAIS