RESISTANCE EXERCISE DECREASES BETA-ENDORPHIN IMMUNOREACTIVITY

Previous research investigating the response of plasma beta-endorphins (beta-EP) to resistance exercise has resulted in equivocal findings. To examine further the effects of resistance exercise on beta-EP immun oreactivity, 10 male and 10 female college-age students participated i n a series of controlled isotonic resistance exercises. The session co nsisted of three sets of eight repetitions at 80% of one repetition ma ximum (1-RM) for each of the following exercises: (1) bench press; (2) lateral pull-downs; (3) seated arm curls; and (4) military press. Blo od plasma was sampled both before and after the lifting routine and be ta-endorphin levels were determined by radioimmunoassay. A Students t test for paired samples indicated that mean(s.e.) plasma beta-endorphi n levels after exercise (10.5(1.3) pg beta-EP ml(-1)) were significant ly decreased as compared with pre-exercise (control) levels (16.5(1.2) , P<0.05). While the mechanism(s) contributing to the decrease in immu noreactivity is unclear, it may be the result of the synergistic effec t of beta-EP clearance during rest intervals and changes in psychologi cal states between sampling.