title: Impact of muscle injury and accompanying inflammatory response on thermoregulation during exercise in the heat.
abstract: This study examined whether muscle injury and the accompanying inflammatory responses alter thermoregulation during subsequent exercise-heat stress. Sixteen subjects performed 50 min of treadmill exercise (45-50% maximal O(2) consumption) in a hot room (40 degrees C, 20% relative humidity) before and at select times after eccentric upper body (UBE) and/or eccentric lower body (LBE) exercise. In experiment 1, eight subjects performed treadmill exercise before and 6, 25, and 30 h after UBE and then 6, 25, and 30 h after LBE. In experiment 2, eight subjects performed treadmill exercise before and 2, 7, and 26 h after LBE only. UBE and LBE produced marked soreness and significantly elevated creatine kinase levels (P < 0.05), but only LBE increased (P < 0.05) interleukin-6 levels. In experiment 1, core temperatures before and during exercise-heat stress were similar for control and after UBE, but some evidence for higher core temperatures was found after LBE. In experiment 2, core temperatures during exercise-heat stress were 0.2-0.3 degrees C (P < 0.05) above control values at 2 and 7 h after LBE. The added thermal strain after LBE (P < 0.05) was associated with higher metabolic rate (r = 0.70 and 0.68 at 2 and 6-7 h, respectively) but was not related (P > 0.05) to muscle soreness (r = 0.47 at 6-7 h), plasma interleukin-6 (r = 0.35 at 6-7 h), or peak creatine kinase levels (r = 0.22). Local sweating responses (threshold core temperature and slope) were not altered by UBE or LBE. The results suggest that profuse muscle injury can increase body core temperature during exercise-heat stress and that the added heat storage cannot be attributed solely to increased heat production.
authors.affiliation: Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts 01760-5007, USA. scott.montain@na.amedd.army.mil
authors.forename: S J
authors.initials: SJ
authors.lastname: Montain
authors.forename: W A
authors.initials: WA
authors.lastname: Latzka
authors.forename: M N
authors.initials: MN
authors.lastname: Sawka
mesh_terms: D000064:Acclimatization; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001831:Body Temperature; D001833:Body Temperature Regulation; D003402:Creatine Kinase / Q000378:metabolism; D015444:Exercise / Q000502:physiology*; D005260:Female; D006358:Hot Temperature; D006801:Humans; D015850:Interleukin-6 / Q000097:blood; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000293:injuries* / Q000378:metabolism; D009220:Myositis / Q000209:etiology / Q000503:physiopathology*; D010146:Pain / Q000209:etiology; D013312:Stress, Physiological / Q000503:physiopathology; D013546:Sweating; D014947:Wounds and Injuries / Q000150:complications / Q000503:physiopathology*
chemical_list: D015850:Interleukin-6; D003402:Creatine Kinase