Comparison of internal temperature responses to prolonged arm and leg ergometer exercise

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Understanding thermoregulatory responses to different modes of exercise has important implications from both experimental and spaceflight‐countermeasure perspectives. It is unknown whether prolonged, dynamic arm or leg exercise at the same metabolic demand (i.e., VO2) will elicit similar internal temperature (Tcore) responses. Six subjects (N=6) completed separate, 60 minute trials of Arm and Leg cycle ergometry. Heart rate (HR), mean arterial pressure (MAP) and Tcore (via pill telemetry) were measured throughout exercise. The exercise workload was determined as follows: Watts = 0.35·Body Mass (kg). The VO2 responses to Arm (10.2±0.5) and Leg (9.9±0.6 ml/kg/min) exercise were not different (p = 0.4). However, HR responses were greater during Arm cycling (87±7) compared to Leg cycling (78±4 bpm) at minute 60 (mode*time interaction, p<0.01). MAP responses only tended to be different between Arm and Leg cycling (p=0.051). Interestingly, Tcore responses were greater during Arm cycling at minutes 40, 50 and 60 (mode*time interaction, p<0.01). Although the greater Tcore responses to Arm exercise were modest (difference of means ~0.1 °C), they are supportive of differences between exercise modes that may be of physiological relevance at both greater exercise intensities and during repeated exercise exposure (e.g., heat acclimation).Support by NASA Grant NNX08AY40G