1227 Journal of Strength and Conditioning Research, 2007, 21(4), 1227–1232  2007 National Strength & Conditioning Association PRE-EXERCISE STRETCHING DOES NOT IMPACT UPON RUNNING ECONOMY PHILIP R. HAYES 1 AND ADRIAN WALKER 2 1 Health, Exercise and Sport Performance Research Group, Division of Sport Sciences, Northumbria University, Newcastle-Upon-Tyne, United Kingdom; 2 Gateshead College, Sports Academy, Gateshead International Stadium, Neilson Road, Gateshead, Tyne and Wear, United Kingdom. ABSTRACT. Hayes, P.R., and A. Walker. Pre-exercise stretching does not impact upon running economy. J. Strength Cond. Res. 21(4):1227–1232. 2007.—Pre-exercise stretching has been widely reported to reduce performance in tasks requiring maximal or near-maximal force or torque. The purpose of this study was to compare the effects of 3 different pre-exercise stretching rou- tines on running economy. Seven competitive male middle and long-distance runners (mean  SD) age: 32.5  7.7 years; height: 175.0  8.8 cm; mass: 67.8  8.6 kg; V ˙ O 2 max: 66.8  7.0 ml·kg -1 ·min -1 ) volunteered to participate in this study. Each participant completed 4 different pre-exercise conditions: (a) a control condition, (b) static stretching, (c) progressive static stretching, and (d) dynamic stretching. Each stretching routine consisted of 2  30-second stretches for each of 5 exercises. De- pendent variables measured were sit and reach test before and after each pre-exercise routine, running economy (ml·kg -1 ·km -1 ), and steady-state oxygen uptake (ml·kg -1 ·min -1 ), which were measured during the final 3 minutes of a 10-minute run below lactate threshold. All 3 stretching routines resulted in an in- crease in the range of movement ( p = 0.008). There was no change in either running economy ( p = 0.915) or steady-state V ˙ O 2 ( p = 0.943). The lack of change in running economy was most likely because it was assessed after a period of submaximal running, which may have masked any effects from the stretch- ing protocols. Previously reported reductions in performance have been attributed to reduced motor unit activation, presum- ably IIX. In this study, these motor units were likely not to have been recruited; this may explain the unimpaired performance. This study suggests that pre-exercise stretching has no impact upon running economy or submaximal exercise oxygen cost. KEY WORDS. warm-up, endurance, oxygen cost INTRODUCTION A number of recent studies have looked at the influence of pre-exercise stretching upon per- formance (2, 8–10, 13, 14, 27, 28, 31, 32, 39). Some studies focused upon purely concentric- work, others examined stretch shortening cy- cle (SSC) activities. The mechanism(s) causing the reduc- tion in performance have yet to be fully elucidated. It is thought that there is a reduction in muscle tendon unit (MTU) stiffness or a reduction in motor unit activation (MUA) as a consequence of the stretching procedure (2, 9, 13, 14, 28, 31–33). Where concentric actions have been employed, there is a unanimous finding of reduced muscle performance after static stretching (2, 13, 14, 28, 31, 32). Most of the studies on concentric muscle actions used performance as the main dependent variable. These papers have, there- fore, been unable to identify the effect of changes in both MTU stiffness and MUA arising from the stretching. In many sporting activities, the muscle actions used are SSC. The evidence for reduced SSC activity after static stretching is less consistent (8, 10, 27, 39). At present, it is unclear whether the same inhibitory mechanisms in- fluence SSC activity. To some extent, this is a reflection of the different SSC activities employed within the stud- ies. Most of these papers (8, 27, 39), however, did not examine both the neural and muscular stiffness changes due to the stretching. Young and Elliott (39) suggested that for activities with short ground-contact times (250 ms) a stiffer MTU would be beneficial. Luhtanen and Komi (29) found con- tact times of 200 ms at velocities typically used by en- durance runners. Based upon the prediction of Young and Elliott (39), this implies that a stiffer MTU would be ben- eficial for endurance runners. This is consistent with pre- vious findings highlighting that less flexible individuals had better movement economy (11, 17, 25). Both Craib et al. (11) and Jones (25) used trained runners finding less- flexible individuals to be more economic. If pre-exercise static stretching increases muscle compliance, then run- ning economy could be compromised. Pre-exercise stretching reduces stretch reflex (33) and H-wave:M-wave ratio (37). These neural changes could effect myoelectric potentiation (5, 6) and thereby SSC performance. The im- pact of any myoelectric potentiation changes during sub- maximal running are, to the best of our knowledge, un- known. Using untrained subjects, Godges et al. (18) examined pre-exercise stretching to increase hip flexion and exten- sion on running economy. They found improved running economy after stretching. This agrees with the general belief that pre-exercise stretching is beneficial to running performance (34). It is in conflict with both the notion of a stiffer MTU being beneficial, and the reduction in per- formance found in other studies employing pre-exercise static stretching. The effect of pre-exercise stretching on running economy in trained runners, therefore, remains unclear. Any increase in running economy would have implications for performance in long-distance events, such as the half marathon and marathon. The purpose of the present study, therefore, was to investigate the effects of pre-exercise stretching techniques on running econo- my. METHODS Experimental Approach to the Problem Previous research has suggested that a stiffer muscle ten- don unit would benefit running economy. This implies that pre-exercise static stretching could have a negative impact upon running economy; to date, this has not been tested. A randomized, counterbalanced, repeated mea- sures design was employed to examine the effects of pre- exercise stretching on running economy. Participants in the study completed 4 different pre-exercise routines.