Effect of active warm-up on metabolism prior to and during intense dynamic exercise SUSAN C. GRAY, GIUSEPPE DEVITO, and MYRA A. NIMMO Strathclyde Institute for Biomedical Sciences, University of Strathclyde, Glasgow, UNITED KINGDOM ABSTRACT GRAY, S. C., G. DEVITO, and M. A. NIMMO. Effect of active warm-up on metabolism prior to and during intense dynamic exercise. Med. Sci. Sports Exerc., Vol. 34, No. 12, pp. 2091–2096, 2002. Purpose: This study investigated whether active warm-up (AW) would increase muscle acetylcarnitine concentration before exercise, thereby reducing the reliance on nonoxidative ATP production during subsequent high-intensity exercise. Methods: Six female subjects performed a 30-s sprint at 120% of their maximal power output on an electronically braked cycle ergometer 5 min after undertaking an active warm-up. To exclude any effect of muscle temperature (T m ) on metabolism, AW was compared with control (C), which involved passively heating the muscle to the same temperature as that achieved by active warm-up (37.1  0.3 vs 37.2  0.2°C AW and C, respectively). Results: Active warm-up significantly increased the concentration of acetylcarnitine from 4.5  1.5 mmol·kg dry muscle (dm) 1 at rest to 9.4  1.6 mmol·kg dm 1 before the onset of exercise. There was no change in acetylcarnitine concentration in C. During exercise the accumulation of muscle lactate was significantly less in AW compared with C (21.9  3.8 vs 34.3  2.3 mmol·kg dm 1 , respectively). Conclusion: The main finding of this study was that there was less accumulation of blood and muscle lactate during intense dynamic exercise preceded by active warm-up, which could not be accounted for by a difference in T m between trials immediately before the onset of exercise Key Words: ACETYLCARNITINE, HIGH-INTENSITY CYCLING, LACTATE, MUSCLE TEMPERATURE W arm-up has been reported to alter the metabolic response during a subsequent exercise bout when compared with control (7,8,18,19). It has been suggested that this response is the result of an increase in blood flow and therefore oxygen (O 2 ) delivery to the active muscles after active warm-up (18). However, a recent study by Bangsbo et al. (1) has shown that O 2 supply to the contracting muscle is in excess of demand in the initial phase of dynamic exercise and that O 2 delivery is not limiting for oxygen uptake (V ˙ O 2 ) of the contracting mus- cles. Thus, it does not seem likely that a differing metabolic response during exercise preceded by warm-up is the result of a difference in O 2 delivery to the active muscle. It has also been proposed that the associated increase in muscle temperature (T m ) during warm-up influences metab- olism during subsequent exercise (7,8,18,21). After passive warm-up, it has been reported that there is an increased dependency on anaerobic metabolism during high-intensity dynamic exercise (8) and an increase in muscle glycogen utilization during submaximal exercise (21). During exer- cise preceded by active warm-up, reductions in the accu- mulation of both blood and muscle lactate concentrations have been observed (10,18,19). Although both Febbraio et al. (8) and Starkie et al. (21) attributed alterations in me- tabolism to a direct effect of T m , Gray and Nimmo (10) observed no difference in blood metabolites during exercise despite a significant difference in T m between passive and control trials immediately before the onset of exercise, sug- gesting that other factors may also be responsible for the observed metabolic alterations during exercise preceded by warm-up. There is evidence to suggest that mitochondrial acetyl group availability may partly determine the relative contri- bution made by anaerobic and oxidative ATP regenerating pathways at the onset of intense skeletal muscle contraction (22,23,24). An increase in muscle acetylcarnitine concen- tration after pharmacological activation of the pyruvate de- hydrogenase complex (PDC) by dichloroacetate (DCA) re- sults in a reduction in PCr degradation and lactate accumulation during exercise in both canine (22,23) and human (14,24) skeletal muscle. It has also been reported in a refereed abstract by Campbell et al. (3) that a low-intensity warm-up (55% V ˙ O 2max ) elevates muscle acetylcarnitine concentration without affecting PCr degradation or lactate accumulation during a subsequent bout of intense exercise (3 min at 90% V ˙ O 2max ). Because the concentration of mus- cle acetylcarnitine has been shown to be related to exercise intensity and increases with increasing intensity (6,13), it is possible that the intensity of active warm-up employed by Campbell et al. (3) did not result in a sufficient increase in acetylcarnitine concentration before the onset of exercise to significantly reduce the reliance on anaerobic metabolism during exercise. Address for correspondence: Dr. Susan Gray, School of Life Sciences, Napier University, Merchiston Campus, 10 Colinton Road, Edinburgh, EH10 5DT, United Kingdom; E-mail: s.gray@napier.ac.uk. Submitted for publication March 2002. Accepted for publication August 2002. 0195-9131/02/3412-2091/$3.00/0 MEDICINE & SCIENCE IN SPORTS & EXERCISE ® Copyright © 2002 by the American College of Sports Medicine DOI: 10.1249/01.MSS.0000039308.05272.DF 2091