Context: Although stretching exercises are commonly used in clinical and athletic practice, there is a lack of evidence regarding the methodological variables that guide the prescription of stretching programs, such as intensity. Objective: To investigate the acute effects of different stretching intensities on the range of motion (ROM), passive torque, and muscle architecture. Design: Two-group pretest–posttest design. Setting: Laboratory. Participants: Twenty untrained men were allocated into the low- or high-intensity group. Main Outcome Measures: Subjects were evaluated for initial (ROMinitial) and maximum (ROMmax) discomfort angle, stiffness, viscoelastic stress relaxation, muscle fascicle length, and pennation angle. Results: The ROM assessments showed significant changes, in both groups, in the preintervention and postintervention measures both for the ROMinitial (P < .01) and ROMmax angle (P = .02). There were no significant differences for stiffness and viscoelastic stress relaxation variables. The pennation angle and muscle fascicle length were different between the groups, but there was no significant interaction. Conclusion: Performing stretching exercises at high or low intensity acutely promotes similar gains in flexibility, that is, there are short-term/immediate gains in ROM but does not modify passive torque and muscle architecture.
Camila Ximenes Santos, Natália Barros Beltrão, André Luiz Torres Pirauá, João Luiz Quagliotti Durigan, David Behm and Rodrigo Cappato de Araújo
Natália Barros Beltrão, Camila Ximenes Santos, Valéria Mayaly Alves de Oliveira, André Luiz Torres Pirauá, David Behm, Ana Carolina Rodarti Pitangui and Rodrigo Cappato de Araújo
Context: Stretching intensity is an important variable that can be manipulated with flexibility training. However, there is a lack of evidence regarding this variable and its prescription in stretching programs. Objective: To investigate the effects of 12 weeks of knee flexor static stretching at different intensities on joint and muscle mechanical properties. Design: A randomized clinical trial. Setting: Laboratory. Participants: A total of 14 untrained men were allocated into the low- or high-intensity group. Main Outcome Measures: Assessments were performed before, at 6 week, and after intervention (12 wk) for biceps femoris long head architecture (resting fascicle length and angle), knee maximal range of motion (ROM) at the beginning and maximal discomfort angle, knee maximal tolerated passive torque, joint passive stiffness, viscoelastic stress relaxation, knee passive torque at a given angle, and affective responses to training. Results: No significant differences were observed between groups for any variable. ROM at the beginning and maximal discomfort angle increased at 6 and 12 weeks, respectively. ROM significantly increased with the initial angle of discomfort (P < .001, effect size = 1.38) over the pretest measures by 13.4% and 14.6% at the 6- and 12-week assessments, respectively, and significantly improved with the maximal discomfort angle (P < .001, effect size = 1.25) by 15.6% and 18.8% from the pretest to the 6- and 12-week assessments, respectively. No significant effects were seen for muscle architecture and affective responses. Initial viscoelastic relaxation for the low-intensity group was lower than ending viscoelastic relaxation. Conclusion: These results suggest that stretching with either low or high discomfort intensities are effective in increasing joint maximal ROM, and that does not impact on ROM, stiffness, fascicle angle and length, or affective response differences.