GOLDFARB, A. H., B. D. HATFIELD, G. A. SFORZO, and M. G. FLYNN. Serum [beta]-endorphin levels during a graded exercise test to exhaustion. Med. Sci. Sports Exerc, Vol. 19, No. 2, pp. 78-82, 1987. Nine untrained college age males completed a graded exercise protocol to maximal capacity on a bicycle ergometer to determine if there was a relationship between intensity of exercise and serum [beta]-endorphin ([beta]-EP) levels. Subjects fasted for 12 h and abstained from physical activity at least 24 h prior to testing. Subjects completed the Multiple Affect Adjective Check List prior to and following exercise to ascertain if psychological state would be associated with [beta]-EP levels. The initial workload was 150 kilopond meters and was increased 150 kilopond meters every 3 min until [latin capital V with dot above]O2max or leg fatigue occurred. Expired gases were continuously analyzed, and a venous blood sample was drawn from an indwelling catheter during the final 30 s of each stage and 5-min post-exercise. [beta]-EP levels were determined from serum using a radioimmunoassay technique and corrected for cross-reactivity with [beta]-lipotropin using affinity chromatography. Resting [beta]-EP levels were 25.3 +/- 4.1 pg[middle dot]ml-1 and did not demonstrate significant changes during any stage of exercise. A correlation analysis (r = 0.30) revealed no significant relationship between exercise intensity and [beta]-EP levels. Following exercise, [beta]-EP levels were significantly increased compared to resting values (38.8 +/- 4.8 pg[middle dot]ml-1). In addition, psychological state was unaffected by exercise despite significant increases in recovery [beta]-EP levels. These data support previous studies reporting increases in [beta]-EP levels following exercise, but do not indicate a relationship between intensity of exercise and [beta]-EP levels during graded exercise or peripheral [beta]-EP levels and psychological state.
(C)1987The American College of Sports Medicine