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In a previous study, we investigated the contribution of the surface of the face, chest, abdomen, and thigh to thermal comfort by applying local temperature stimulation during whole-body exposure to mild heat or cold. In hot conditions, humans prefer a cool face, and in cold they prefer a warm abdomen. In this study, we extended investigation of regional differences in thermal comfort to the neck, hand, soles, abdomen (Experiment 1), the upper and lower back, upper arm, and abdomen (Experiment 2). The methodology was similar to that used in the previous study. To compare the results of each experiment, we utilized the abdomen as the reference area in these experiments. Thermal comfort feelings were not particularly strong for the limbs and extremities, in spite of the fact that changes in skin temperature induced by local temperature stimulation of the limbs and extremities were always larger than changes that were induced in the more proximal body parts. For the trunk areas, a significant difference in thermal comfort was not observed among the abdomen, and upper and lower back. An exception involved local cooling during whole-body mild cold exposure, wherein the most dominant preference was for a warmer temperature of the abdomen. As for the neck and abdomen, clear differences were observed during local cooling, while no significant difference was observed during local warming. We combined the results for the current and the previous study, and characterized regional differences in thermal comfort and thermal preference for the whole-body surface.

This study compared cardiovascular responses to static extension and flexion exercises at four upper and lower limb joints. Eight males performed a 2 min static contraction at 30% of maximal voluntary torque followed immediately by 2 min post-exercise muscle ischaemia (PEMI) using each of four joints: the wrist, elbow, ankle, and knee. In the PEMI, an occlusion cuff placed around the proximal portion of the exercising muscle was inflated to 250 mmHg immediately before the cessation of exercise. Mean arterial pressure (MAP), heart rate (HR), calf blood flow, and calf vascular conductance (CVC) in the non-exercised calf were measured. There was a significant interaction for direction of movement (extension vs. flexion) and limb (upper vs. lower) in HR and CVC during both exercise and PEMI; extension in the wrist and elbow evoked a greater increase in HR and a greater decrease in CVC than flexion, whereas flexion in the ankle and knee elicited a greater increase in HR and a greater decrease in CVC than extension. These results suggest that the cardiovascular responses to extension and flexion differ between arms and legs, partly arising from the activation of the muscle metaboreflex.

To test whether changes in oxygenation of a resting skeletal muscle, evoked by a static contraction in a contralateral muscle, is uniform within a given skeletal muscle, we used near-infrared spectroscopy (NIRS). Seven subjects performed 2 min static knee extension exercise at 30% of maximal voluntary contraction. Changes in oxygenated hemoglobin (HbO(2)) were monitored using multiple-channel NIRS (40 channels, 13 sources and 12 detectors) attached on the contralateral nonexercising triceps surae muscle. Changes in HbO(2) were expressed as a percentage of total labile signals. To characterize the distribution of changes in HbO(2), channels were compared between their positions on the triceps surae muscle, and represented as 'proximal versus distal' and 'lateral versus medial' portions. During static muscle contraction, the averaged changes in HbO(2) of all channels were correlated with those in calf blood flow (plethysmography; R (2)=0.188, P<0.05) and with calf vascular conductance (R (2)=0.146, P<0.05). HbO(2) did not differ significantly between the lateral and medial portions of the triceps surae muscle. In contrast, the decrease of HbO(2) in the proximal portion of the muscle was greater than that of the distal portion (P<0.05). These results indicate that the changes in oxygenation of a resting muscle, evoked by static contraction of the contralateral muscle, are heterogeneous.