Eur J Appl Physiol (2008) 102:533–538 DOI 10.1007/s00421-007-0618-1 123 ORIGINAL ARTICLE Muscle sympathetic nerve activity at rest compared to exercise tolerance Arto J. Hautala · Antti M. Kiviniemi · Timo H. Mäkikallio · Suvi Tiinanen · Tapio Seppänen · Heikki V. Huikuri · Mikko P. Tulppo Accepted: 6 November 2007 / Published online: 22 November 2007  Springer-Verlag 2007 Abstract Cardiovascular autonomic function is associ- ated with physical performance and exercise training adap- tation. The association between physical performance and sympathetic regulation is not well known. We hypothesized that sympathetic nervous system activity is associated with physical performance among male runners. The study pop- ulation included 26 healthy male club runners [age 33 § 5 years, body mass index (BMI) 24 § 1 kg/m 2 , VO 2max 58 § 5 ml kg ¡1 min ¡1 ; mean § SD]. Muscle sym- pathetic nerve activity (MSNA) was assessed from the peroneal nerve by the microneurography technique during 5 min of supine rest. Physical performance was assessed by time to exhaustion during treadmill running. The mean rest- ing MSNA was 20 § 6 bursts min ¡1 (range 6–34). The mean time to exhaustion was 1,005 § 136 s (range 720– 1260). When the study group was divided into tertiles according to their running performance (866 § 69, 994 § 30 and 1154 § 71 s in time to exhaustion, P < 0.0001 between the groups), MSNA was lower (P = 0.032) in the group with the best running performance (16 § 5 bursts min ¡1 ) compared to those with the worst running performance (23 § 7 bursts min ¡1 ). In conclusion, baseline sympathetic activity, measured by a microneurog- raphy at rest, may be associated with the maximal running performance of healthy subjects. Keywords Microneurography · Autonomic nervous system · Physical performance Introduction Physical Wtness and exercise training are associated with changes in cardiovascular autonomic regulation. The altered cardiovascular autonomic regulation after an exer- cise training intervention is manifested as a decreased heart rate (HR) and increased beat-to-beat HR variability as evi- dence of enhanced vagal outXow to the heart (Goldsmith et al. 1997; Hautala et al. 2004; Levy et al. 1998; Tulppo et al. 1998, 2003). The sympathetic arm of the autonomic nervous system plays a key role in the regulation of cardiovascular homeo- stasis. Direct measurement of muscle sympathetic nerve activity from the peroneal nerve by the microneurography (MSNA) has provided information about autonomic regula- tion in various clinical and physiological settings (Wallin and Charkoudian 2007). The associations between MSNA and physical performance remain equivocal, however. Cross-sectional studies have revealed either a positive corre- lation between resting MSNA and physical Wtness (Alvarez et al. 2005; Ng et al. 1994) or no association at all (Seals 1991; Svedenhag et al. 1984). Training intervention studies have reported increased (Sinoway et al. 1992), decreased (Grassi et al. 1994; Ray 1999), or unchanged resting MSNA A. J. Hautala (&) · A. M. Kiviniemi · M. P. Tulppo Department of Exercise and Medical Physiology, Verve Research, Kasarmintie 13, PO Box 404, 90101 Oulu, Finland e-mail: arto.hautala@verve.W A. J. Hautala · A. M. Kiviniemi · T. H. Mäkikallio · H. V. Huikuri · M. P. Tulppo Division of Cardiology, Department of Internal Medicine, University of Oulu, Oulu, Finland S. Tiinanen · T. Seppänen Department of Electrical and Information Engineering, University of Oulu, Oulu, Finland T. H. Mäkikallio Lapland Central Hospital, Rovaniemi, Finland