Kinematic and Neuromuscular Measures of Intensity During Drop Jumps in Female Volleyball Players
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2021
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The aim of this study was to assess drop jump (DJ) performance variables (jump height,
contact time, and reactive strength index) concomitant to surface electromyography
(sEMG) of lower limb muscles during DJs from different drop heights (intensities).
The eccentric and concentric phase sEMG from the gastrocnemius medialis, biceps
femoris, and vastus medialis muscles were assessed during all tests, with sEMG
activity normalized to maximal voluntary isometric contraction (MVIC). In a crosssectional,
study, 10 amateur female volleyball players (age 22.1 1.8 years; body mass
72.9 15.2 kg; height 1.70 0.08 m) completed DJs from six heights [15–90 cm
(DJ15 to DJ90)]. During DJs there was no jump-target box to rebound on to. Results of
one-way analysis of variance (ANOVA) showed that the jump height, contact time, and
reactive strength index were not significantly (p > 0.05) different between drop heights.
Mean biceps femoris eccentric and concentric sEMG ranged from 27 to 50%, although
without significant differences between drop heights. Mean gastrocnemius medialis
eccentric and concentric sEMG remained relatively constant ( 60–80% MVIC) across
DJs heights, although eccentric values reached 90–120% MVIC from DJ75 to DJ90.
Mean variations of 50–100% MVIC for eccentric and 50–70% MVIC for concentric
sEMG activations were observed in the vastus medialis across DJs heights. The biceps
femoris eccentric/concentric sEMG ratio during DJ45 (i.e., 1.0) was lower (p = 0.03)
compared to the ratio observed after DJ90 (i.e., 3.2). The gastrocnemius medialis and
vastus medialis eccentric/concentric sEMG ratio were not significantly different between
drop heights. In conclusion, jumping performance and most neuromuscular markers
were not sensitive to DJ height (intensity) in amateur female volleyball athletes.