241 Journal of Strength and Conditioning Research, 2001, 15(2), 241–246  2001 National Strength & Conditioning Association Inhibition of Maximal Voluntary Isokinetic Torque Production Following Stretching Is Velocity-Specific ARNOLD G. NELSON, 1 IVAN K. GUILLORY, 1 ANDREW CORNWELL, 2 AND JOKE KOKKONEN 3 1 Department of Kinesiology, Louisiana State University, Baton Rouge, Louisiana 70803; 2 Department of Kinesiology and Physical Education, California State University-Los Angeles, Los Angeles, California 90032; 3 Physical Education Division, Brigham Young University-Hawaii Campus, Laie, Hawaii 96762. ABSTRACT Recent research has shown that a regimen of stretching pro- vides an acute inhibition of maximal force production by the stretched muscle group. To further characterize this phenom- enon, the effect of an acute stretching regimen on maximal isokinetic knee-extension torque at 5 specific movement ve- locities (1.05, 1.57, 2.62, 3.67, and 4.71 rad· s -1 ) was examined in 10 men and 5 women (22–28 years). Each person’s 5 base- line maximal isokinetic knee-extension torques (dominant leg) were measured on a Cybex NORM dynamometer. Fol- lowing the baseline torque measurements, the participants stretched the dominant quadriceps for 15 minutes using 1 active and 3 passive stretching exercises. Once the stretching exercises were completed, the maximal torque measurements were repeated. Poststretch maximal torque at 1.05 rad·s -1 was significantly reduced (p  0.05) from 218  47 Nm (mean  SD) to 199  49 Nm (7.2% decrease). At 1.57 rad·s -1 , a similar decrease (p  0.05) was also seen (204  48 Nm vs. 195  47 Nm; 4.5% decrease), but at the other velocities (2.62, 3.67, and 4.71 rad·s -1 ), poststretch maximal torque was unaltered (p  0.05). It appears, therefore, that the deleterious impact of stretching activities on maximal torque production might be limited to movements per- formed at relatively slow velocities. Key Words: isokinetic contraction, flexibility, strength loss, warm-up Reference Data: Nelson, A.G., I.K. Guillory, A. Corn- well, and J. Kokkonen. Inhibition of maximal voluntary isokinetic torque production following stretching is ve- locity-specific. J. Strength Cond. Res. 15(2):241–246. 2001. Introduction A lthough stretching exercises designed to enhance flexibility are regularly included in both the train- ing programs and the pre-event warm-up activities of most athletes, research exists that suggests pre-exercise stretching could have a negative impact on the perfor- mance of skills where success is related to maximal force or torque output (1, 3, 9). For example, Fowles and Sale (3) found that maximum isometric plantar- flexion torque about the ankle joint was decreased by 28% immediately after the plantar flexors were pas- sively stretched. A decrement in maximum torque was also present 60 minutes after stretching, albeit to a lesser degree (9%). In addition, stretching has been shown to elicit a strength deficit in concentric muscle actions. Kokkonen et al. (9) reported that a regimen of acute static stretching inhibited the 1 repetition maxi- mum (1RM) lift of both knee extension (8% decrease) and knee flexion (7% decrease). The mechanism(s) re- sponsible for such strength decrements following a bout of passive, static stretching, however, is (are) not clear. Acute increases in flexibility as a result of stretching have been attributed to both neurophysio- logical and mechanical factors (7). Consequently, a re- duction in maximal force/torque output poststretch- ing might be related to a change in neural or mechan- ical status. Studies of static stretching have consistently re- ported decreases in motoneuron excitability during stretching as measured by the Hoffman-reflex (H-re- flex; 2, 4). It is not apparent, however, if this depres- sion in motoneuron excitability persists once a stretch is terminated. Some studies have found a significant mean decrease in the H-reflex immediately after stretching (1, 15), whereas others have not (4, 16). Until more conclusive evidence is available, it is possible that a reduction in maximal force output following stretch- ing could be related to a decrease in neuromuscular function. Nevertheless, we suggest that such a mechanism is probably not the prevailing cause of stretch-induced