Acute effect of static stretching on older women isometric force-time curve during single and multiple joint exercise

Abstract

During the aging process are observed changes in the neuromuscular system that causes decreased of different components of functional capacity, among them, flexibility. Accordingly, the stretching exercises have been recommended by the literature as a means of mitigating / reversing such declines. Anyway, recent studies show acute deleterious effects of stretching on different expressions of muscle strength. However, no definitive conclusion can be adopted with respect to such behavior, since the authors have used different stretching routines. Moreover, it has been demonstrated that changes in muscle strength can be exercise-dependent. Most studies examined the effect of stretching on muscle strength in young subjects. Thus, the aim of this study is to analyze the acute effect of stretching on the older women isometric force-time curve during single and multiple joint exercise. Participants in this study, 30 elderly women, participants of a regular program of physical exercises generalized (frequency of three times a week). Each participant will visit the laboratory for three non-consecutive days. Participants will be instructed to not perform any intense physical activity in the 24 hours preceding the measures. The first visit will aim to familiarize the procedures adopted in the measure of the isometric force-time curve exercises leg press and extension chair (extension of the knee). Also be determined on the first day, the anthropometric measurements of participants and places for fixing the electrodes used to record the EMG activity. In two subsequent visits (an interval of 48 hours between visits), the registration of the isometric force-time curve EMG activity will be conducted in the Leg Press or the extensor chair, chosen at random (control condition) (C). In the same session, after 30 minutes of interval, the participants will be subjected to static stretch (3x30 seconds to the femoral quadriceps), and the isometric force-time curve and isometric EMG activity, agonist muscles vastus medialis (VM) and vastus lateralis (VL ) and antagonist biceps femoral (BF) will be evaluated in the following intervals: immediately, 1 minute after (1m-post), 2 minutes (2m-post), 4 minutes (4m-post), 8 minutes (-8m post) and 16 minutes (16m-post) (stretching condition) (A). In order to avoid circadian variations in the behavior of muscle strength, all participants come to the place where the evaluation at the same time. For the treatment of data will be used descriptive statistics (mean and standard deviation). Once verified the normal distribution of data by Shapiro Wilk test, will be used ANOVA for repeated measures 2x2. Subsequently, the post-hoc Bonferroni test applied. Once rejected the normal distribution of data, the comparison between the conditions will be performed by the Wilcoxon test. The significance level will be p d 0.05. (AU)