CHARACTERIZATION OF THE PROLACTIN RESPONSE TO PROLONGED ENDURANCE EXERCISE

This study characterized the blood prolactin responses to a prolonged endurance exercise bout in comparison to a resting, control period with no exercise. Six healthy exercise trained males completed both a 90 minute cycle exercise (70% VO_2max) and a rest-control experimental session under standardized conditions. Blood samples were collected at - 15, 0 (exercise start), 15, 30, 45, 60, 75, 90 (exercise end), 105, and 120 minute time points in the exercise and rest-control sessions. Prolactin concentrations were analyzed using radioimmunoassay procedures and tested for significant changes with ANOVA analysis. In the exercise session, prolactin concentrations from 45 to 120 minutes were significantly greater than the 15 minute concentration before exercise (p < 0.01). Furthermore, the exercise concentrations at 45 to 120 minutes were also significantly greater than the concentrations observed at the comparable rest-control time points (p < 0.01; approximately 300% elevation). The frequent blood sampling protocol used in this study clearly portrays the magnitude, time-line, and extend of the prolactin response to prolonged endurance activity. The mechanism and role for the prolactin response was not the focus of this study, but relative to the latter, it is speculated the hormonal change could pertain to signaling energy usage-status within the body and, or prompting immune system activation.