Effect of long-term physical training on total red cell volume

Abstract

Six months of military training elicited a significant 4% mean increase in total red cell volume (TRCV) measured by the ⁵¹Cr-labelled red cell method. This increase was associated with a mean 16% increase in predicted maximal oxygen uptake (VO₂max). The increases in TRCV and predicted VO₂max were inversely related to their initial levels. A statistically highly significant correlation between TRCV and predicted VO₂max was observed (r = 0.59). The trained group had larger initial TRCVs than the sedentary group and the subjects who became well conditioned had a significant increase in TRCV, which contrasted with the unchanged TRCV in the subjects who did not become well conditioned. The greatest increase in TRCV (11%) was found in corporals, who had the hardest training. A statistically significant correlation between the changes in TRCV and estimated plasma volume was observed (r = 0.62, P < 0.001). Owing to the 1.8% increase in body weight the TRCV and predicted VO₂max in terms relative to the body weight did not demonstrate the changes as clearly as did the absolute values. The factors affecting the TRCV increase are discussed.

Key Words:

• physical fitness
• plasma volume
• red cell mass