Running Elevates Plasma β-Endorphin Immunoreactivity and ACTH in Untrained Human Subjects

Abstract Twenty minutes of submaximal treadmill running was associated with an elevation in plasma levels of β-endorphin immunoreactivity (P < 0.02). This increase was greater in men (14.9 ± 3.4 fmole/ml) than women (2.6 ± 1.2 fmole/ml) (P < 0.05). Plasma levels of ACTH and growth hormone also increased after running. ACTH increased more in men (7.8 ± 1.1 fmole/ml) than in women (1.1 ± 0.44 fmole/ml) (P < 0.02). There was a similar growth hormone response in both sexes. No correlation can at this time be made with levels in the central nervous system. Changes in plasma levels of β-endorphin immunoreactivity may be responsible for some of the euphoria and analgesia anecdotally associated with running.