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Men worked (BMR 190 kcal/m2 hr) in the heat (45–50 C D.B.; 26 C W.B.) for periods of 5–7 hr, maintaining water and salt balance by drinking appropriate saline solutions. d-Aldosterone was administered by continuous intravenous infusion at 1.5 µg/kg hr during the third to seventh hours without altering the Na or Cl concentration of the men's sweat from control values determined during the first 2 hr of the exposures, or from the values observed during separate control experiments. Na and Cl concentrations of sweat secreted the day following the infusion experiments were not significantly different from those of samples collected the day after control experiments. The sodium-conserving responses of the men's sweat glands 7–24 hr following salt depletion (-140 to -230 mEq) were not significantly altered by infusion of 2.0–4.5 µg/kg hr of d-aldosterone. Continuous infusion of d-aldosterone at 1.8 µg/kg hr into one brachial artery did not alter the Na or Cl concentration of sweat being secreted by the infused arm, either from simultaneously collected samples from the man's other arm or from control values in both arms before the infusion was started. In all cases, pronounced reductions in urinary Na:K ratios were observed during and after d-aldosterone administration. Submitted on October 28, 1963

Determination of time relations of changes in oxygen consumption, oxygen debt, blood lactate of physically trained and untrained humans during aerobic work and recovery

Men worked on a treadmill for periods of 5, 5, 10, 10, 10 and 10 min, stopping for 2 min between work periods to be weighed. Finger and mean skin temperatures decreased at the beginning of work (10 mets). When room temperature was 25 C vasodilation occurred in the finger in the third work period as gastrocnemius muscle and femoral vein temperatures reached maximal values. Temperatures of skin and saphenous vein blood rose rapidly as the men reclined during the rest periods and decreased when work was resumed, coinciding with changes of femoral temperature in the opposite directions. These rapid shifts in temperature indicate that during the rest periods the proportion of blood coming from the skin into the trunk of the femoral was greater than during the work periods. The onset of sweating, the rate of its increase in the early stages of these work experiments, and its decline in recovery more nearly paralleled corresponding changes in femoral temperature than any of the other temperatures measured. exercise; femoral vein temperature; temperature regulation; saphenous vein temperature; skin temperature Submitted on October 5, 1964

The work capacity at sea level and high altitude has been measured on nine men, five of whom had taken part in similar studies at high altitudes from 18 to 33 years earlier. Except for a few measurements on the treadmill at sea level each subject rode the bicycle ergometer; the brakeload was increased minute-by-minute until his limit was reached. The maximum capacity for oxygen intake declined with age both at high altitude and at sea level. Individual responses varied greatly: the most fit individual, age 54, had about as great an oxygen intake on the ergometer at Pb 455 mm Hg as had a man one-half his age at sea level. After 5 or 6 weeks of acclimatization a man of 71 attained at Pb 485 a greater oxygen intake per minute and per kilogram than that of a man of 27. At that barometric pressure the limiting oxygen intake on the bicycle ergometer may be only one-half of the sea-level value 2 or 3 days after arrival; after 4–6 weeks it may range from two-thirds to five-sixths of the sea-level value. adaptation to altitude; altitude and heart rate; altitude and maximum O2 intake; altitude and respiratory volume Submitted on November 4, 1963