A lack of muscle flexibility affects the functionality of the human body, making it difficult to carry out certain activities of daily living. The aim of the present study was to compare the technique of passive static stretching on hamstring muscles in isolation, or combined with heating techniques and different application times. Fifty women were randomly assigned to 5 groups (n = 10 each): The Microwave Diathermy Group had the hamstrings heated by microwave before stretching; Treadmill Group, in which warm-up walking was performed before stretching; 30-Second Group, in which 30 s of stretching was performed; 10-Minute Group, which involved stretching for 10 min and Control Group. In all groups, the leg extension range of motion was assessed, and the flexibility by the third finger-ground test was performed before and after application. The individuals in the experimental groups performed three stretching sessions on three consecutive days. All statistical analysis was performed with p ≤ 0.05. The results showed that all treatments were effective compared to the control group. The Treadmill Group and the 10-Minute group were superior for an acute effect (soon after the stretch--related to a decreased muscular viscoelasticity). The 10-Minute Group was the most effective for the chronic effect (long lasting--related to increased numbers of sarcomeres). A 10-minute stretch, when performed over four subsequent days, is suggested for faster increase in flexibility. The results could suggest a systemic warming (such as the one provided by a treadmill workout) before stretching for an acute gain of flexibility in the same day. It was possible to identify the inefficiencies associated with the use of microwaves in terms of stretching to gain flexibility. In fact, the values recorded were similar to stretching without any heat at all.
Keywords: Flexibility; Microwave; Range of motion; Stretching.
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