Abstract
The present study assessed the impacts of two distinct protocols, static
stretching (StS, 4 sets of 30 seconds) and static stretching combined with
conditioning contractions (10 repetitive drop jumps) (SC), on neuromuscular
response and rate of force development (RFD) in the lower limbs during squat
jumps (SJs) at varying initial knee-joint angles (60°,90°,120°). Twelve
participants completed three randomized experimental trials (no intervention,
StS intervention, and SC intervention). Except for the intervention segments,
each trial included standardized warm-ups and SJs at three different angles.
Data were collected using a 3-dimensional injury motion capture system, an
electromyography (EMG) recording system, and a force platform. The collected EMG
data were subjected to amplitude calculations, while force-time data were used
for RFD computation. Neither StS nor SC significantly impacted the average or
peak EMG amplitudes of the five muscles examined (p>0.05). However, at an
initial knee-joint angle of 120°, the StS group demonstrated significantly lower
RFD values at three distinct phases (0–50 ms, 50–100 ms, and 0–peakforce)
compared to those seen in the SC and control groups (p<0.05). For activities
starting with a knee-joint angle of 120°, it is recommended to either avoid StS
or combine it with ten repetitive drop jumps to mitigate any potential negative
impact on explosiveness.
Keywords
electromyography - muscle activation - rate of force development - force-time characteristics
