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Acute effects of static versus dynamic stretching on isometric peak torque, electromyography, and mechanomyography of the biceps femoris muscle
by
Herda TJ, Cramer JT, Ryan ED, McHugh MP, Stout JR.
—
last modified
2009-10-09 15:17
J Strength Cond Res. 2008 May;22(3):809-17.
The purpose of this study was to examine the acute effects of static versus
dynamic stretching on peak torque (PT) and electromyographic (EMG), and
mechanomyographic (MMG) amplitude of the biceps femoris muscle (BF) during
isometric maximal voluntary contractions of the leg flexors at four different
knee joint angles. Fourteen men ((mean +/- SD) age, 25 +/- 4 years) performed two
isometric leg flexion maximal voluntary contractions at knee joint angles of 41
degrees , 61 degrees , 81 degrees , and 101 degrees below full leg extension. EMG
(muV) and MMG (m x s(-2)) signals were recorded from the BF muscle while PT
values (Nm) were sampled from an isokinetic dynamometer. The right hamstrings
were stretched with either static (stretching time, 9.2 +/- 0.4 minutes) or
dynamic (9.1 +/- 0.3 minutes) stretching exercises. Four repetitions of three
static stretching exercises were held for 30 seconds each, whereas four sets of
three dynamic stretching exercises were performed (12-15 repetitions) with each
set lasting 30 seconds. PT decreased after the static stretching at 81 degrees (p
= 0.019) and 101 degrees (p = 0.001) but not at other angles. PT did not change
(p > 0.05) after the dynamic stretching. EMG amplitude remained unchanged after
the static stretching (p > 0.05) but increased after the dynamic stretching at
101 degrees (p < 0.001) and 81 degrees (p < 0.001). MMG amplitude increased in
response to the static stretching at 101 degrees (p = 0.003), whereas the dynamic
stretching increased MMG amplitude at all joint angles (p </= 0.05). These
results suggested that the decreases in strength after the static stretching may
have been the result of mechanical rather than neural mechanisms for the BF
muscle. Overall, an acute bout of dynamic stretching may be less detrimental to
muscle strength than static stretching for the hamstrings.