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The purpose of this research was to determine the effect of a 7-day heat acclimation protocol on HSP-72 expression in human skeletal muscle, and to examine the relationships between molecular and physiological markers of heat acclimation. Ten recreationally active male subjects (age = 23.3 +/- 2.81 yrs, VO(2peak) = 3.85 +/- 0.11 L . min (-1)) completed a 7-day heat acclimation protocol consisting of cycling at 75 % of VO(2peak) in a hot environment (39.5 degrees C, 27 % RH). Muscle biopsies were obtained on days 1 (HTT1) and 7 (HTT2) prior to, 6 h post, and 24 h postexercise to measure HSP-72 protein via SDS-PAGE and silver staining. Core rectal temperatures (T(C)), intramuscular temperatures (T(IM)), skin temperatures (T(SK)), heart rate (HR), oxygen uptake (VO(2)), sweat rate (SR), and plasma cortisol were measured. TC, HR, and plasma cortisol were significantly lower in HTT2 than HTT1 (p < or = 0.05). No significant differences were seen for VO(2), TIM, TSK, or SR when comparing HTT2 with HTT1 (p < or = 0.05). No significant time or day x time interactions were detected for HSP-72 expression (24.48 +/- 2.55 vs. 25.04 +/- 1.43 ng/microg protein for HTT1 and HTT2, respectively, p < or = 0.05). Evidence of heat acclimation was seen at the physiological level; however, no evidence of enhanced thermotolerance at the cellular level was indicated by HSP-72 expression.

The purpose of this study was to investigate the differences between lactate thresholds determined from venous and arterialized blood. Seven endurance-trained college males performed an incremental bicycle ergometer exercise test until exhaustion. At the end of each 3 min stage, blood was sampled simultaneously from a hyperemized ear-lobe and an antecubital vein for the measurement of blood lactate (La-). Two-minute rest intervals separated each stage. Arterialized blood La-concentrations ([La-]) were significantly higher than venous blood at 350 W (14.5 and 9.7 mmol.l-1), maximal exercise (15.5 and 11.39 mmol.l-1), and throughout recovery. Arterialized [La-] was significantly higher than venous blood at the onset of blood La- accumulation (OBLA) (4.0 and 2.8 +/- 0.1 mmol.l-1), the individual anaerobic threshold (IAT) (3.4 +/- 0.3 and 2.1 +/- 0.1 mmol.l-1), and the ventilatory threshold (VT) (4.7 +/- 0.9 and 3.2 +/- 0.6 mmol.l-1). No significant differences were found between either La-threshold for arterialized or venous blood. The oxygen consumption (VO2) at OBLA was significantly lower when determined from arterialized blood La (2.3 +/- 0.2 and 2.8 +/- 0.2 l.min-1). No significant differences existed between the LT, OBLA, and IAT threshold-VO2 determinations from arterialized blood; however, significant differences were found between IAT-OBLA (2.1 +/- 0.2 and 2.8 +/- 0.2 l.min-1) and LT (2.2 +/- 0.2 l.min-1)-OBLA from venous blood. These results indicate that differences between venous and arterialized blood [La-] need to be considered when comparing different anaerobic threshold determinations.

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