INTRODUCTION:
The preparation for sports activities often involves warm-up and/or stretching in order to prevent injuries and/or improve performance. However, how these practices may interfere with neuromuscular mechanisms of joint control is unclear.
OBJECTIVE:
To analyze the immediate effect of stretching and warm-up exercises, alone or combined, on muscle latency time (MLT) and hamstrings activation amplitude after sudden knee joint disturbances.
METHODS:
Sixty female volunteers (mean age 22.3±1.7 years, BMI 21.4±1.3kg/cm2)were randomly divided into four groups: (1) control, (2) warm-up, (3) stretching, (4) warm-up + stretching. Hamstrings electrical activity was recorded by surface electromyography during a sudden knee disturbance. An electrogoniometer detected the onset of angular variation, while electrodes recorded the onset and amplitude of muscle activity before and after interventions. Two-way ANOVA and post hoc Tukey were used in statistical analysis, considering a significance level of p<0.05.
RESULTS:
The MLT of the biceps femoris and semitendinosus muscles was reduced in groups 3 (p=0.048 and 0.027, respectively), and 4 (p=0.026 and 0.039, respectively). There was no significant change in the amplitude of muscle activation amplitude in the evaluated groups.
CONCLUSIONS:
The results of this study suggest that although no changes in electromyographic amplitude were observed, static and passive stretching used alone or in combination with warm-up, caused a reduction in the hamstrings MLT. This reduction may prove to be a protective factor for muscle and joint injuries, after a sudden disturbance, such as those that occur in sports.
electromyography; reaction time; proprioception
