Heat shock protein (HSP-72) levels in skeletal muscle following work in heat.
BACKGROUND
Acute bouts of heat stress and exercise have been shown to independently increase heat shock protein levels; however, the combination of these two stressors on HSP-72 expression in human skeletal muscle has not been established. The purpose of this study was to determine the effect of a bout of exercise in the heat on HSP-72 expression.


METHODS
There were eight recreationally active men (Age = 26.4 +/- 3.1 yr, V(O2)peak = 4.01 +/- 0.25 L min(- 1)) who completed two 30-min bouts of cycle ergometry at 75% of V(O2)peak in a hot (39 degrees C; RH 30%) and cold (9 degrees C; RH 61%) environment. Muscle biopsies were obtained from the vastus lateralis prior to, 6 h post, and 24 h post-exercise to measure HSP-72 protein. Core rectal temperature (Tc), average skin temperature (T(SK)), intramuscular temperature (T(IM)), heart rate (HR), oxygen uptake (V(O2)), sweat rate (SR), and plasma cortisol were measured to determine thermal loads.


RESULTS
No significant interactions were present between V(O2) (2.80 +/- 0.2 vs. 2.65 +/- 0.1 L min(-1)) or plasma cortisol (27.1 +/- 2 vs. 19.2 +/- 4 microg dl(-1)) when comparing HT and CD. HR (184 +/- 5 vs. 159 +/- 7 bpm), T(IM) (40.7 +/- 0.2 vs. 40.0 +/- 0.2 degrees C), Tc (38.3 +/- 0.2 vs. 37.9 +/- 0.1 degrees C), T(SK) (36.7 +/- 0.2 vs. 29.6 +/- 0.8 degrees C), and SR (2.0 +/- 0.2 vs. 1.2 +/- 0.2 L h(-1)) were significantly greater when comparing HT and CD. HSP-72 was not altered as a result of either treatment (4.04 +/- 0.87 vs. 2.91 +/- 1.58 ng microg(-1) protein for HT and CD at 6 h post-exercise).


CONCLUSIONS
Exercise in the heat produced a greater thermal load than exercise in the cold; however, no significant increases in HSP-72 were seen when comparing hot and cold conditions.
Watkins
Austen M
AM
Department of Kinesiology, Texas Christian University, Fort Worth, TX 76129, USA.
Cheek
Dennis J
DJ
Harvey
Alison E
AE
Goodwin
John D
JD
Blair
Kara E
KE
Mitchell
Joel B
JB
D000222:Adaptation, Physiological; D000328:Adult; D001831:Body Temperature / Q000502:physiology*; D017079:Exercise Tolerance / Q000502:physiology; D050884:HSP72 Heat-Shock Proteins / Q000378:metabolism*; D006358:Hot Temperature; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D010101:Oxygen Consumption; D005082:Physical Exertion / Q000502:physiology*
D050884:HSP72 Heat-Shock Proteins; D006854:Hydrocortisone