Affiliations: Laboratory of Biomechanics, São Paulo State University, UNESP, Rio Claro-SP, Brazil
Correspondence:
[*]
Corresponding author: Pedro V.S. Moreira, Av: 20 A, n°1199, Vila Indaiá, Rio Claro-SP, 13506-710 Brazil. E-mail:[email protected]
Abstract: BACKGROUND: Hamstrings:quadriceps (H:Q) strength muscular
imbalances are frequently associated with injuries.
OBJECTIVE: To investigate the H:Q ratio dependencies of the fatigue
effect induced by an exhaustive isokinetic exercise.
METHODS: Nineteen male soccer players were evaluated, before and
after exhaustive isokinetic exercises, for electromechanical delay (EMD),
root mean square (RMS), median frequency (MF), and rate of electromyographic
rise (RER) of the rectus femoris (RF), vastus lateralis (VL), vastus
medialis (VM), biceps femoris (BF), semitendinosus (ST), isometric peak torque (PT) and
rate of torque development (RTD) of the knee extensors (KE)
and knee flexors (KF). The fatigue effect was measured by paired dependent
tests, with a significance level of p < 0.05.
RESULTS: RTD and PT were reduced (23-38%), with an H:Q reduction
of RTD100 ms by 21%. In PT, antagonist RMSVL and RMSRF
decreased by 32-39%, but at 0-50 ms, 0-100 ms and 0-200 ms, agonist
RMSRF diminished by > 32%. At 0-50 ms and 0-100 ms, the antagonist
RMSVM improved by > 149%. RERRF and RERST diminished in both
0-50 ms and 0-100 ms (38-41%), while RERBF decreased
at 0-50 ms (30%). Agonist MFRF and MFBF in PT decreased by
9-10%.
CONCLUSION: Neuromuscular fatigue due to maximal isokinetic
concentric voluntary contractions affects the hamstrings more than the
quadriceps in terms of producing rapid torque.
