DIFFERENTIAL EFFECTS OF 30- VS. 60-SECOND STATIC MUSCLE STRETCHING ON VERTICAL JUMP PERFORMANCE MATHEUS D. PINTO, 1 EURICO N. WILHELM, 1 VALMOR TRICOLI, 2 RONEI S. PINTO, 1 AND ANTHONY J. BLAZEVICH 3 1 Exercise Research Laboratory, Physical Education School, Federal University of Rio Grande do Sul, Porto Alegre, Brazil; 2 Laboratory of Neuromuscular Adaptations to Strength Training, School of Physical Education and Sport, University of Sa˜o Paulo, Sa˜o Paulo, Brazil; and 3 Center for Exercise and Sports Science Research, School of Exercise and Health Sciences, Edith Cowan University, Joondalup, Australia ABSTRACT Pinto, MD, Wilhelm, EN, Tricoli, V, Pinto, RS, and Blazevich, AJ. Differential effects of 30- vs. 60-second static muscle stretch- ing on vertical jump performance. J Strength Cond Res 28(12): 3440–3446, 2014—It has been proposed that pre-exercise static stretching may reduce muscle force and power. Recent systematic and meta-analytical reviews have proposed a thresh- old regarding the effect of short (,45 seconds) and moderate ($60 seconds) stretching durations on subsequent perfor- mance in a multi-joint task (e.g., jump performance), although its effect on power output remains less clear. Furthermore, no single experimental study has explicitly compared the effect of short (e.g., 30 seconds) and moderate (60 seconds) durations of continuous static stretching on multi-joint performance. Therefore, the aim of the present study was determine the effect of acute short- and moderate-duration continuous stretching interventions on vertical jump performance and power output. Sixteen physically active men (21.0 6 1.9 years; 1.7 6 0.1 m; 78.4 6 12.1 kg) volunteered for the study. After familiarization, subjects attended the laboratory for 3 testing sessions. In the nonstretching (NS) condition, subjects per- formed a countermovement jump (CMJ) test without a preced- ing stretching bout. In the other 2 conditions, subjects performed 30-second (30SS; 4 minutes) or 60-second (60SS; 8 minutes) static stretching bouts in calf muscles, ham- strings, gluteus maximus, and quadriceps, respectively, followed by the CMJ test. Results were compared by repeated-measures analysis of variance. In comparison with NS, 60SS resulted in a lower CMJ height (23.4%, p # 0.05) and average (22.7%, p # 0.05) and peak power output (22.0%, p # 0.05), but no difference was observed between 30SS and the other conditions (p . 0.05). These data suggest a dose-dependent effect of stretching on muscular perfor- mance, which is in accordance with previous studies. The pres- ent results suggest a threshold of continuous static stretching in which muscular power output in a multi-joint task may be impaired immediately following moderate-duration (60 sec- onds; 8 minutes) static stretching while short-duration (30 sec- onds; 4 minutes) stretching has a negligible influence. KEY WORDS stretch volume, countermovement jump, muscular performance, muscle power INTRODUCTION M uscle power is considered a critical element for successful athletic performance (24). One way to indirectly evaluate multi-joint lower limb power production is through the use of the countermovement jump (CMJ) test. For example, Tillin et al. (29) found significant correlations between CMJ height, sprint performance, and squat rate of force development in rugby players, indicating a reasonable similarity in the factors underpinning their performances. However, an adequate level of flexibility is also a potentially important physical attribute influencing athletic performance, thus stretching exercises organized to improve flexibility are usually included in training and performance-preparation programs by individuals who require high power outputs. Indeed, a recent study demonstrated that static stretching is com- monly used during training sessions and before competitions by recreational and competitive athletes (14). One reason indicated for its use is to decrease delayed onset muscle sore- ness (DOMS) (11), despite the prevailing evidence that stretching before an event does not reduce DOMS (8). A second, and possibly more important, reason is that stretch- ing may increase muscle-tendon unit compliance, which was reported to be altered after short periods (e.g., 5 seconds) of Address correspondence to Matheus D. Pinto, matheus.daros@ufrgs.br. 28(12)/3440–3446 Journal of Strength and Conditioning Research Ó 2014 National Strength and Conditioning Association 3440 Journal of Strength and Conditioning Research the TM Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.