GONADAL-HORMONES AND SEMEN QUALITY IN MALE RUNNERS - A VOLUME THRESHOLD EFFECT OF ENDURANCE TRAINING

Eleven high mileage runners (HR) (108.0 +/- 4.5 km.wk(-1)), 9 moderate mileage runners (MR) (54.2 +/- 3.7 km.wk(-1)) and 10 sedentary contro ls (SC) of similar age (28.3 +/- 1.5 yr) were studied to evaluate the effects of volume of endurance training on reproductive function in ma le runners. Levels of reproductive, adrenal and thyroid hormones were measured during a 1-hr period of serial blood sampling (q20 min) and u rinary excretion of 24-hr luteinizing hormone (uLH) was determined on two separate days. Semen exams and sperm penetration of standard cervi cal mucus (Penetrak) were performed 2-5 times. Levels of total testost erone (TT) and free testosterone (FT) were significantly lower in HR ( 15.3 +/- 1.3 nmol.l(-1) and 60.2 +/- 5.1 pmol.l(-1)) compared to MR (2 1.4 +/- 1.6 nmol.l(-1) and 86.0 +/- 6.1 pmol.l(-1)) and SC (19.5 +/- 0 .9 nmol.l(-1) and 75.9 +/- 3.6 pmol.l(-1)). No differences (p > 0.05) were found in uLH, serum LH, follicle-stimulating hormone (FSH), and p rolactin (PRL) among the three groups. No other hormonal differences ( p > 0.05) were observed among the groups. Total motile sperm count and density were lower (p < 0.05) in HR than SC. Decreased (p < 0.0006) s perm motility and an increased (p < 0.004) population of immature sper m and round cells were observed in HR compared to MR and SC. Sperm pen etration of bovine cervical mucus was also decreased (p < 0.024) in HR compared to SC. Volume of training, defined by km wk(-1) run, was sig nificantly correlated to sperm motility, density and number of round c ells. TT was significantly correlated to number of round cells. These findings suggest that well defined differences in reproductive functio n exist between HR and MR, including decreased gonadal steroids and di sturbed semen quality that is not observed in runners participating in more moderate volumes of training. Thus, a 'volume-threshold' effect of training is apparently coincident with high volumes of endurance ru nning.