MENU ▼
Read by QxMD icon Read
search
OPEN IN READ APP
JOURNAL ARTICLE

Effects of training and acclimation on heat tolerance in exercising men wearing protective clothing

Y Aoyagi, T M McLellan, R J Shephard
European Journal of Applied Physiology and Occupational Physiology 1994, 68 (3): 234-45
8039520
This study examined the effectiveness of endurance training and heat acclimation in reducing the physiological strain imposed by exercising in the heat while wearing protective clothing. Seven young men underwent 8 weeks of physical training [60-80% maximal aerobic power (VO2max) for 30-45 min.day-1, 3-4 days.week-1 at < 25 degrees C] followed by 6 days of heat acclimation (45-55% VO2max for 60 min.day-1 at 40 degrees C, 30% relative humidity). Nine other young men underwent corresponding periods of control observation and heat acclimation. Before and after each treatment, subjects completed a treadmill walk (4.8 km.h-1, 2% grade) in a climatic chamber (40 degrees C, 30% relative humidity), wearing in turn normal combat clothing or clothing protecting against nuclear, biological, and chemical (NBC) agents. Criteria for halting this test were: (1) a rectal temperature (T(re)) of 39.3 degrees C; (2) a heart rate (fc) > or = 95% of the subject's observed maximum, maintained for 3 min; (3) unwillingness of the subject to continue; (4) the elapse of 120 min. The training regimen increased mean VO2max by 16% and mean plasma volume by 8%. When tested in normal combat clothing, the rates of increase in T(re) and fc were slower after training. However, when wearing NBC protective clothing, the only significant change induced by training was a higher mean skin temperature (Tsk) in the early part of the test. Heat acclimation increased the mean plasma volume of untrained subjects by 8%, but their VO2max remained unchanged. When tested in normal combat clothing, acclimation decreased their mean values of T(re), Tsk, fc, and metabolic rate. When wearing NBC protective clothing, the only significant decrease after acclimation was in overall T(re). In trained subjects, heat acclimation induced no further improvement in any physiological variable when wearing normal combat clothing, but reduced overall T(re) and Tsk when wearing NBC protective clothing. Training- or acclimation-induced increases of sweat secretion (an average increment of 0.14-0.23 kg.h-1) were not accompanied by any statistically significant increase in sweat evaporation when wearing NBC protective clothing. Moreover, tolerance times were unchanged in either normal combat (116-120 min) or NBC protective clothing (47-52 min). We conclude that neither endurance training nor heat acclimation do much to improve exercise tolerance when wearing NBC protective clothing in hot environments, because any added sweat secretion decreases blood volume and increases discomfort without augmenting body cooling.

Comments

You need to log in or sign up for an account to be able to comment.

No comments yet, be the first to post one!

Trending on Read

Available on the App Store

Available on the Play Store
Remove bar
Read by QxMD icon Read
8039520
×

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"