Maurice Jetté

The effect of ambient temperature and exercise intensity on post-exercise thermal homeostasis

Abstract We have previously demonstrated a prolonged (65 min or longer) elevated plateau of esophageal temperature (Tes) (0.5–0.6°C above pre-exercise values) in humans following heavy dynamic exercise (70% maximal oxygen consumption, V˙O2max) at a thermoneutral temperature (Ta) of 29°C. The elevated Tes value was equal to the threshold Tes at which active skin vasodilation was initiated during exercise (Thdil). A subsequent observation, i.e., that successive exercise/recovery cycles (performed at progressively increasing pre-exercise Tes levels) produced parallel increases of Thdil and the post-exercise Tes, further supports a physiological relationship between these two variables. However, since all of these tests have been conducted at the same Ta (29°C) and exercise intensity (70% V˙O2max) it is possible that the relationship is limited to a narrow range of Ta/exercise intensity conditions. Therefore, five male subjects completed 18 min of treadmill exercise followed by 20 min of recovery in the following Ta/exercise intensity conditions: (1) cool with light exercise, Ta = 20°C, 45% V˙O2max (CL); (2) temperature with heavy exercise, Ta = 24°C, 75% O2 max (TH); (3) warm with heavy exercise, Ta = 29°C, 75% V˙O2max (WH); and (4) hot with light exercise, Ta = 40°C, 45% V˙O2max (HL). An abrupt decrease in the forearm-to-finger temperature gradient (Tfa −Tfi) was used to identify the Thdil during exercise. Mean pre-exercise Tes values were 36.80, 36.60, 36.72, and 37.20°C for CL, TH, WH, and HL conditions respectively. Tes increased during exercise, and end post-exercise fell to stable values of 37.13, 37.19, 37.29, and 37.55°C for CL, TH, WH, and HL trials respectively. Each plateau value was significantly higher than pre-exercise values (P < 0.05). Correspondingly, Thdil values (i.e., 37.20, 37.23, 37.37, and 37.48°C for CL, TH, WH, and HL) were comparable to the post-exercise Tes values for each condition. The relationship between Thdil and post-exercise Tes remained intact in all Ta/exercise intensity conditions, providing further evidence that the relationship between these two variables is physiological and not coincidental.

Physiological effects of inspiratory resistance on progressive aerobic work

SummaryThe purpose of this study was to determine the potential effects on progressive aerobic work while breathing through a new military type chemical and biological (CB) respirator loaded with three different types of purifying canisters. Twelve healthy well-motivated male subjects (mean age 23±3 years) participated in the study. Results indicated that mean maximal oxygen uptake

Reproducibility of body temperature response to standardized test conditions when assessing clothing.

(\dot V_{O_{2{\text{ max}}} } )

Effect of inspiratory resistance to prolonged exercise in a hot environment wearing protective clothing

, time to exhaustion, respiratory exchange ratio, rate of perceived exertion, respiratory rate and tidal volume at exhaustion, maximal lactate and the 2-min post-exercise lactate were not significantly influenced when breathing with the respirator and the canisters in comparison to a laboratory valve. Mean pulmonary ventilation, however, was reduced by 21% while oxygen and carbon dioxide ventilatory equivalents were significantly lower by 9% and 8% respectively. Review of the stage-by-stage responses to the treadmill test between the laboratory valve and respirator/canister conditions indicated no significant differences (NS) in oxygen uptake but slightly lower heart rates (NS). Ventilation was not influenced by the canisters until 80% of

Anthropometric and Selected Motor Fitness Measurements of Men Engaged in a Long-Term Program of Physical Activity.

\dot V_{o_{2{\text{ }}max} }

The Canadian Home Fitness Test as a predictor for aerobic capacity.

at which time the mean oxygen ventilatory equivalent became significantly lower. Blood lactate was significantly depressed between 60% and 90%