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The aim of the present study was to determine the combined effects of pre-cooling and water ingestion on thermoregulatory responses and exercise capacity at 32 degrees C and 80% relative humidity. Nine untrained males exercised for 60 min on a cycle ergometer at 60% maximal oxygen uptake (VO2max) (first exercise bout) under four separate conditions: No Water intake, Pre-cooling, Water ingestion, and a combination of pre-cooling and water ingestion (Combined). To evaluate the efficacy of these conditions on exercise capacity, the participants exercised to exhaustion at 80% VO2max (second exercise bout) following the first exercise bout. Rectal and mean skin temperatures before the first exercise bout in the Pre-cooling and Combined conditions were significantly lower than in the No Water and Water conditions. At the end of the first exercise bout, rectal temperature was lower in the Combined condition (38.5 +/- 0.1 degrees C) than in the other conditions (No Water: 39.1 +/- 0.1 degrees C; Pre-cooling: 38.7 +/- 0.1 degrees C; Water: 38.8 +/- 0.1 degrees C) (P < 0.05). Heat storage was higher following pre-cooling than when there was no pre-cooling (P < 0.05). The final rectal temperature in the second exercise bout was similar between the four conditions (39.1 +/- 0.1 degrees C). However, exercise time to exhaustion was longer (P < 0.05) in the Combined condition than in the other conditions. Total sweat loss was less following pre-cooling than when there was no pre-cooling (P < 0.001). Evaporative sweat loss in the Water and Combined conditions was greater (P < 0.01) than in the No Water and Pre-cooling conditions. Our results suggest that the combination of pre-cooling and water ingestion increases exercise endurance in a hot environment through enhanced heat storage and decreased thermoregulatory and cardiovascular strain.

A cross-sectional survey examined whether habitual endurance exercisers retained a higher level of T cell function than sedentary individuals in old age. Subjects, all male, comprised 17 elderly runners, 16 young, and 19 elderly controls (mean ages +/- SD: 63.8 +/- 3.3, 23.6 +/- 1.6, and 65.8 +/- 3.5 yr, respectively), whose resting blood samples served for the immunological tests. Compared with the young subjects, both elderly groups had lower circulating CD3+ and CD8+ cell-counts (P = 0.029, P = 0.001, respectively), with a trend to a higher CD4/CD8 ratio, but higher percentages of activated CD3+, and "memory" CD4+ and CD8+ cells (all, P < 0.0001). Proliferative responses to phytohemagglutinin, pokeweed mitogen, and alloantigens were markedly reduced in the elderly (P < 0.001, and P = 0.024, respectively). IL-2 production tended to be decreased in the elderly sedentary subjects. However, natural killer cell activity and other cytokine production remained unchanged in the elderly sedentary subjects. Comparison between the active and sedentary elderly groups showed no differences in circulating counts of immunocompetent cells. However, the active elderly subjects demonstrated significantly greater proliferative responses to phytohemagglutinin ( P = 0.016) and to pokeweed mitogen (P = 0.011), and higher rates of IL-2 (P = 0.021), IFN-gamma (P = 0.015) and IL-4 production (P = 0.012). These results suggest that endurance training in later life is associated with a lesser age-related decline in certain aspects of circulating T cell function and related cytokine production.

We evaluated changes in body temperature, heart rate, and oxygen uptake during arm cranking exercise (20 watts, 30 min) in an artificial climate room at a temperature of about 25 degrees C or 35 degrees C (relative humidity, about 50%) in 5 patients with paraplegics due to spinal cord injury (SCI). The tympanic temperature (Tty) was significantly higher from rest to recovery at 35 degrees C than at 25 degrees C. The mean Tty after 10 minutes of rest was 36.68 degrees C +/- 0.396 (mean +/- SD) at a room temperature of 25 degrees C and 37.25 degrees C +/- 0.253 at 35 degrees C, showing a difference of about 0.5 degrees C. This difference was maintained during exercise and recovery. The Tty at the end of exercise was higher than that at the start of exercise by 0.66 degrees C +/- 0.218 (mean +/- SD) at 25 degrees C and by 0.59 degrees C +/- 0.210 at 35 degrees C. The skin temperature (Tsk) in each measurement area (the head, arm, chest, thigh, shin, and calf) was significantly higher at 35 degrees C. Oxygen uptake did not differ between 25 degrees C and 35 degrees C. The heart rate was significantly higher at 35 degrees C than at 25 degrees C during rest and at the start of exercise but did not differ during exercise and recovery. Thus, mild-moderate exercise in this study did not cause marked changes such as increases in body temperature and heart rate that affect biological function in SCI.(ABSTRACT TRUNCATED AT 250 WORDS)

Five male subjects performed steady exercise on a cycle ergometer at an intensity of 60% maximal O2 uptake (VO2max) for 6 min on three separate occasions while breathing gas mixtures of 12,16 or 21% O2 in N2. Expired gas fractions, ventilation, heart rate, arterial O2 saturation (SaO2), blood lactate (La) and plasma catecholamines (epinephrine: E and norepinephrine: NE) were measured. O2 uptake (VO2) was calculated for the last minute of exercise. Blood samples were drawn at rest and immediately after exercise. By inspiring hypoxic gas mixtures, the SaO2 value decreased during exercise to 85.0 +/- 5.4 (16%) and 66.4 +/- 4.1 (12%) from 95.0 +/- 0.1 in normoxia. VO2 during exercise was not different among the three conditions. Exercise-induced La accumulation was increased by hypoxia. E and NE during exercise were not affected by hypoxia statistically. There was a significant correlation between La and E (P < 0.01) and between La and NE (P < 0.01) during exercise in the three conditions. The present findings suggest a relationship between glycogen metabolism and sympathoadrenal activity which results in an increase of plasma catecholamines during exercise in humans acutely exposed to hypoxia.

The purpose of this study was to clarify the effect of the level of spinal cord injury (SCI) and of daily exercise on the relationship between heart rate (HR) and oxygen uptake (VO2) in persons with SCI (PSCI) during an arm cranking exercise. Eighteen PSCI were divided into three groups according to the level of SCI; 4 quadriplegics (C6-C8), 7 high- level paraplegics (T3-T8), and 7 low-level paraplegics (T10-L2). In the relationship between HR and VO2, the higher the level of SCI, the smaller the slope of regression line, that means the HR at a given VO2 become larger as level of SCI was higher. Significant differences were found among these regression lines (P < 0.01). In addition, the regression lines between HR and VO2 in active persons tended to shift toward upper in comparison with those in inactive persons. The present investigation clearly shows that the HR-VO2 relationship in PSCI is remarkably influenced by the level SCI and physical training.