Eur J Appl Physiol DOI 10.1007/s00421-006-0331-5 123 ORIGINAL ARTICLE Attenuation of muscle damage by preconditioning with muscle hyperthermia 1-day prior to eccentric exercise K. Nosaka · M. Muthalib · A. Lavender · P. B. Laursen Accepted: 11 October 2006  Springer-Verlag 2006 Abstract This study investigated the hypothesis that muscle damage would be attenuated in muscles sub- jected to passive hyperthermia 1 day prior to exercise. Fifteen male students performed 24 maximal eccentric actions of the elbow Xexors with one arm; the opposite arm performed the same exercise 2–4 weeks later. The elbow Xexors of one arm received a microwave dia- thermy treatment that increased muscle temperature to over 40°C, 16–20 h prior to the exercise. The contra- lateral arm acted as an untreated control. Maximal vol- untary isometric contraction strength (MVC), range of motion (ROM), upper arm circumference, muscle soreness, plasma creatine kinase activity and myoglo- bin concentration were measured 1 day prior to exer- cise, immediately before and after exercise, and daily for 4 days following exercise. Changes in the criterion measures were compared between conditions (treat- ment vs. control) using a two-way repeated measures ANOVA with a signiWcance level of P < 0.05. All measures changed signiWcantly following exercise, but the treatment arm showed a signiWcantly faster recov- ery of MVC, a smaller change in ROM, and less muscle soreness compared with the control arm. However, the protective eVect conferred by the diathermy treatment was signiWcantly less eVective compared with that seen in the second bout performed 4–6 weeks after the ini- tial bout by a subgroup of the subjects (n = 11) using the control arm. These results suggest that passive hyperthermia treatment 1 day prior to eccentric exer- cise-induced muscle damage has a prophylactic eVect, but the eVect is not as strong as the repeated bout eVect. Keywords Microwave · Muscle temperature · Muscle soreness · Isometric strength · Creatine kinase · Myoglobin · Heat shock proteins Introduction Unaccustomed eccentric exercise induces muscle dam- age; the typical symptoms of which include delayed onset muscle soreness (DOMS), prolonged decreases in muscle function, and swelling (Clarkson et al. 1992; Proske and Morgan 2001). These symptoms are atten- uated however when the same eccentric exercise is performed several weeks beforehand (Clarkson et al. 1992; Nosaka et al. 2005). This protective eVect con- ferred by a single bout of eccentric exercise has often been referred to as the repeated bout eVect (Clarkson et al. 1992). The mechanisms underlying the repeated bout eVect are not clearly understood, but several the- ories have been documented. In his review, McHugh (2003) categorized the potential adaptations caused by K. Nosaka (&) · M. Muthalib · P. B. Laursen School of Exercise, Biomedical and Health Sciences, Edith Cowan University, 100 Joondalup Drive, Joondalup, WA 6027, Australia e-mail: k.nosaka@ecu.edu.au M. Muthalib e-mail: m.muthalib@ecu.edu.au P. B. Laursen e-mail: p.laursen@ecu.edu.au A. Lavender Department of Physiology School of Molecular and Biomedical Science, The University of Adelaide, Adelaide, Australia e-mail: andrew.lavender@adelaide.edu.au