2007 Volume 67 Issue 5 Pages 414-421
High intensity and resistance exercises such as running and weight training reportedly increase beta-endorphin (BE) levels in venous blood. Although these reports suggest that several types of exercises may affect nervous-endocrine systems and result in an increase of BE levels, the precise mechanisms by which exercises cause changes in BE levels are unknown. Since the intensity, frequency, and duration are considered the most important kinetic elements, we examined these three elements on BE production using experimental animals. F344 male rats were exercised on a treadmill and BE levels in the hypothalamus were examined by enzyme-linked immunosorbent assay (ELISA) . Training at more than 25 m/min but not less than 20 m/min caused a significant increase in BE levels in the hypothalamus. Although no significant changes in BE levels were observed in rats subjected to training at 10 m/min twice and three times per day, training at 20 m/min twice and three times per day significantly increased BE levels. Furthermore, training at 20 m/min for 7 to 28 days also caused an increase in BE levels in the hypothalamus. These results strongly suggest that exercise may affect the central nervous system and cause an increase in BE levels in the hypothalamus.
