Langenfeld, M. E., L. S. Hart, and P. C. Kao. Plasma [beta]-endorphin responses to one-hour bicycling and running at 60% [latin capital V with dot above]O2max. Med. Sci. Sports Exerc, Vol. 19, No. 2, pp. 83-86, 1987. Ten adult male volunteers were studied to examine the effect on plasma [beta]-endorphin (B-EN) of bicycling and running for 1 h at 60% [latin capital V with dot above]O2max. All subjects were physically active and accustomed to both exercise modes (mean [latin capital V with dot above]O2max in ml[middle dot]kg-1[middle dot]min-1; bicycling, 54; running, 59).
Following preliminary [latin capital V with dot above]O2max tests, subjects participated in randomly ordered experimental sessions of bicycling and running for 1 h at loads requiring 60% of their mode-specific [latin capital V with dot above]O2max. Five subjects also participated in control sessions. Blood samples were collected immediately pre- and immediately post-exercise, and hematocrits were determined. Samples were centrifuged, separated, and plasma was stored at -50[degrees]C until analysis for B-EN. Analysis involved separation of B-EN from [beta]-lipotropin by short column chromatography followed by radioimmunoassay. Despite an observed trend for elevated B-EN following exercise, there were no significant pre- to post-exercise differences (P > 0.05) in mean B-EN levels in any of the three sessions. Expressed as percentage change in B-EN, there were no significant differences between bicycling, running, or control. These results indicate that 1 h bicycling or running exercise at 60% [latin capital V with dot above]O2max does not consistently increase B-EN, and that responses are variable between individuals.
(C)1987The American College of Sports Medicine