K. B. Pandolf

A physiological strain index to evaluate heat stress

A physiological strain index (PSI), based on rectal temperature (Tre) and heart rate (HR), capable of indicating heat strain online and analyzing existing databases, has been developed. The index rates the physiological strain on a universal scale of 0-10. It was assumed that the maximal Tre and HR rise during exposure to exercise heat stress from normothermia to hyperthermia was 3 degrees C (36.5-39.5 degrees C) and 120 beats/min (60-180 beats/min), respectively. Tre and HR were assigned the same weight functions as follows: PSI = 5(Tret - Tre0) . (39.5 - Tre0)-1 + 5(HRt - HR0) . (180 - HR0)-1, where Tret and HRt are simultaneous measurements taken at any time during the exposure and Tre0 and HR0 are the initial measurements. PSI was applied to data obtained from 100 men performing exercise in the heat (40 degrees C, 40% relative humidity; 1.34 m/s at a 2% grade) for 120 min. A separate database representing seven men wearing protective clothing and exercising in hot-dry and hot-wet environmental conditions was applied to test the validity of the present index. PSI differentiated significantly (P < 0.05) between the two climates. This index has the potential to be widely accepted and to serve universally after extending its validity to women and other age groups.

Differentiated Ratings of Perceived Exertion during Physical Exercise

The typical overall (undifferentiated) rating of perceived exertion (RPE) appears to represent an individuals integration of various physiological sensations that have different subjective weightings. Two categories of physiological factors have been suggested as major determinants of RPE during physical exercise. These two factors are a local factor that relates to sensations or feelings of strain from the exercising muscles and/or joints and a central factor relating primarily to cardiopulmonary sensations. This paper attempts to characterize the relative importance of the various physiological cues in the exertional rating pertinent to these local and central factors. The majority of the related literature suggests that local factors are usually perceived as dominant; however, recent findings that evaluate differentiated RPE during exercise at high altitude imply a greater importance for central factors. When a particular physiological cue is markedly altered over others during exercise, it appears that the resultant sensation can easily dominate the overall RPE. In contrast, when this particular cue is not changed during exercise, as the result of some experimental manipulation or intervention, then another cue can become pronounced. Finally, an experimental model for evaluating differentiated RPE that allows comparisons between local and central exertion and further comparison to the general or overall exertion is discussed.

Predicting Sweat Loss Response to Exercise, Environment and Clothing

SummaryMetabolic heat production (M), clothing heat transfer characteristics, and the environment dictate a required evaporative cooling (Ereq) from the body to maintain thermal balance. However, the maximal evaporative capacity (Emax) is dictated by vapor transfer properties of the clothing and environment. Relationships between metabolic load, environmental conditions, clothing and sweat loss were studied in 34 heat-acclimatized males categorized into four groups (eight, eight, eight, and ten subjects) and exposed to various environmental conditions (ambient temperature, 20–54‡ C, and relative humidity, 10–90%), three levels of metabolic rate (resting; walking 1.34 m·s−1, level; or walking 1.34 m·s−1, 5% grade) while wearing various clothing ensembles (shorts and T-shirts, fatigues, fatigues plus overgarment, or sweat suit). Individual groups were not exposed to all combinations. Exposures lasted 120 min: either 10 min rest — 50 min exercise — 10 min rest — 50 min exercise, or 120 min at rest. Physiological measurements included heart rate, rectal temperature, mean skin temperature, energy expenditure and sweat loss (δmsw). Emax and Ereq were calculated from environmental conditions, metabolism, clothing insulation and permeability. The ratio Ereq/δmsw was found to correlate with Emax and not with M. The predictive equation for sweat loss was: δmsw=18.7×Ereq×(Emax)−0.455 within the limits 50

Influence of heat stress and acclimation on maximal aerobic power

SummaryThirteen male volunteers performed cycle ergometer maximal oxygen uptake (

Erythrocyte, plasma, and blood volume of healthy young men

\dot V_{{\text{O}}_{{\text{2max}}} }

Prediction modeling of physiological responses and human performance in the heat

tests) in moderate (21‡ C, 30% rh) and hot (49‡ C, 20% rh) environments, before and after a 9-day heat acclimation program. This program resulted in significantly decreased (P<0.01) final heart rate (24 bt·min−1) and rectal temperature (0.4‡ C) from the first to last day of acclimation. The

Differentiated ratings of perceived exertion and various physiological responses during prolonged upper and lower body exercise

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