Effects of Dynamic or Static Stretching Performed Before Resistance Training on Muscle Adaptations in Untrained Men

Abstract

Stretching and resistance exercises are often recommended due to their positive effects on health and quality of life. Stretching exercises are frequently performed before a session of resistance exercise, however, muscle stretching has been shown to acutely reduce muscular strength, and impair chronic muscular adaptations to training. However, the chronic effects of static stretching exercises performed prior to bouts of resistance exercise are conflicting. Additionally, the chronic effects of dynamic stretching on muscle adaptations to resistance training remain unknown. Therefore, research that evaluates the chronic effects of both static and dynamic muscle stretching before resistance exercise is needed. PURPOSE: To evaluate the chronic effects of dynamic and static stretching performed before resistance training on muscle adaptations in untrained young men. METHODS: Forty-five untrained young men (21.2±0.5 yrs., 72.2±5.6 kg and 178±1 cm) were randomly assigned to one of three groups: 1) static stretching (SS, n= 14) in which subjects performed 80s of static stretching prior to resistance exercise; 2) dynamic stretching (DS, n= 13) that included 80s of dynamic stretching prior resistance exercise; or 3) control group (CON, n= 18) in which subjects performed no stretching prior to exercise. All subjects performed 4 sets of 8-12RM (repetition maximum) of knee flexion exercise two days per week for 8 weeks, with a period of at least 48 h between sessions. Unilateral knee flexor maximal isometric strength (MIS) and posterior leg muscle thickness (MT) were measured before and after the training period. Data normality was confirmed by the Shapiro-Wilk test and a two-way repeated measures ANOVA (group x time) was performed. Statistical significance was set a priori at p≤ 0.05. RESULTS: There were significant increases in MIS (SS= 48.3%, DS= 37.6%, CON= 49.4%, p< 0.05) and MT (SS= 13.3%, DS= 13.1%, Control= 11.4%, p< 0.05) with no significant differences across groups (p> 0.05). CONCLUSIONS: Eighty seconds of static or dynamic muscle stretching performed prior to bouts of resistance exercise did not affect the training-induced muscular adaptations in untrained young men. Supported by FAPEMIG and IF Sudeste MG- Brazil.