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Effect of Endurance Training and Heat Acclimation on Aerobic Capacity, Blood Volume and Plasma Testosterone.

Pivarnik J. M.; Goetting, M. P.; Senay, L. C. Jr.
Journal of Strength & Conditioning Research: May 1987
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The influence of endurance training and heat acclimation (ET/A) on blood volume and plasma testosterone was examined in 16 healthy males. Each performed a peak VO2 test on a cycle ergometer and had his blood volume (BV) estimated with carbon monoxide. All subjects then participated in an ET/A program which consisted of cycling 90 minutes per day, 6 days per week, at 60 percent of peak VO2 Ambient temperature was 20 degrees celsius for the first 3 weeks and 40 degrees celsius for the final week (rh = 30%-35%). Peak VO2 and BV estimates were repeated following ET/A. Plasma was obtained from a resting venous blood sample. Testosterone concentration ([T]) was measured before and after ET/A using a solid-phase I-125 radioimmunoassay. Peak VO2 improved 12.4 percent and BV increased 13.2 percent after ET/A. Red cell mass and plasma volume increased proportionally. There were no significant changes in either mean [T] or testosterone content (T) following ET/A. There was a significant negative correlation between initial testosterone levels and individual [T] (r = .68) and T (r = .76) changes. This suggests that individuals with low initial values would be more likely to show increases in both [T] and T following ET/A. It appears that changes in peak VO2 and BV following ET/A occurred independently of plasma testosterone levels. The results of this investigation appear to indicate that for untrained males, the combination of endurance training and heat acclimation, rather than an increase in plasma testosterone is the primary stimulus for an increase in peak VO2 and blood volume.

(C) 1987 National Strength and Conditioning Association