GENDER DIFFERENCES IN MUSCULOTENDINOUS STIFFNESS AND RANGE OF MOTION AFTER AN ACUTE BOUT OF STRETCHING KATHERINE M. HOGE, 1 ERIC D. RYAN, 2 PABLO B. COSTA, 1 TRENT J. HERDA, 1 ASHLEY A. WALTER, 1 JEFFREY R. STOUT, 3 AND JOEL T. CRAMER 1 1 Biophysics Laboratory, Department of Health and Exercise Science, University of Oklahoma, Norman, Oklahoma; 2 Applied Musculoskeletal and Human Physiology Laboratory, Department of Health and Human Performance, Oklahoma State University, Stillwater, Oklahoma; and 3 Metabolism and Body Composition Laboratory, Department of Health and Exercise Science, University of Oklahoma, Norman, Oklahoma ABSTRACT Hoge, KM, Ryan, ED, Costa, PB, Herda, TJ, Walter, AA, Stout, JR, and Cramer, JT. Gender differences in musculoten- dinous stiffness and range of motion after an acute bout of stretching. J Strength Cond Res 24(10): 2618–2626, 2010—The purpose of the present study was to examine musculotendinous stiffness (MTS) and ankle joint range of motion (ROM) in men and women after an acute bout of passive stretching. Thirteen men (mean 6 SD age = 21 6 2 years; body mass = 79 6 15 kg; and height = 177 6 7 cm) and 19 women (21 6 3 years; 61 6 9 kg; 165 6 8 cm) completed stretch tolerance tests to determine MTS and ROM before and after a stretching protocol that consisted of 9 repetitions of passive, constant-torque stretching. The women were all tested during menses. Each repetition was held for 135 seconds. The results indicated that ROM increased after the stretching for the women (means 6 SD pre to post: 109.39° 6 10.16° to 116.63° 6 9.63°; p # 0.05) but not for the men (111.79° 6 6.84° to 113.93° 6 8.15°; p . 0.05). There were no stretching-induced changes in MTS (women’s pre to postchange in MTS: 20.35 6 0.38; men’s MTS: +0.17 6 0.40; p . 0.05), but MTS was higher for the men than for the women (MTS: 1.34 6 0.41 vs. 0.97 6 0.38; p # 0.05). electromyographic amplitude for the soleus and medial gastrocnemius during the stretching tests was un- changed from pre to poststretching (p . 0.05); however, it increased with joint angle during the passive movements (p # 0.05). Passively stretching the calf muscles increased stretch tolerance in women but not in men. But the stretching may not have affected the viscoelastic properties of the muscles. Practitioners may want to consider the possible gender differ- ences in passive stretching responses and that increases in ROM may not always reflect decreases in MTS. KEY WORDS constant torque, viscoelastic properties, electro- myography INTRODUCTION S tretching is commonly used to improve perfor- mance (2,49,51,52) and reduce the risk of injury (5,18,47) before athletic events. It has been suggested that stretching will decrease the amount of strain through a range of motion (ROM), thereby reducing the risk of injury (12,44,53). A stiffer musculotendinous unit (MTU) is thought to better withstand large and rapid forces better than a compliant system, thus reducing the likelihood of injury (9,20,29,35). However, there is little evidence to support the relationship between increased flexibility and reduced incidence of injury (25,26,54,55). Yet, a recent study by Shehab et al. (48) found that stretching routines are still performed by high-school athletes as an injury prevention strategy. In addition, there is little research indicating that stretching improves performance. An acute bout of static stretching has been found to reduce muscle strength (14,22) and power (11), impair balance (3), and increase movement and reaction times (3). In addition, a study by Nelson and Kokkonen (37) asked subjects before testing whether stretching would have a beneficial or detrimental outcome, and all subjects believed that an acute bout of stretching would result in better performance. However, because of the limited evidence supporting stretching before competition, the President’s Council for Physical Fitness and Sports released a statement concluding that stretching may not prevent injury and may also compromise performance (27). Despite the discrepancy between knowledge and practice, stretching is still a major component of preactivity warm-up routines, and therefore, additional research is necessary to determine the precise effects of stretching on injury prevention. Address correspondence to Dr. Joel T. Cramer, jcramer@ou.edu. 24(10)/2618–2626 Journal of Strength and Conditioning Research Ó 2010 National Strength and Conditioning Association 2618 Journal of Strength and Conditioning Research the TM Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.