Maintenance of testosterone status in fitness joggers after increased training mileage

The primary objective was to evaluate the early effect of increased training mileage on testosterone (T) status in recreational joggers. Serum total (T(tot)) and free (T(free)) concentrations at rest, overnight urinary T(tot) excretion, and the T(tot) and T(free) responses to maximal exercise were used as indicators of T status. A group of 13 male [mean (SD) age 24.5 (2.5) years] fitness joggers [maximal oxygen consumption, VO(2max), 52.9 (4.9) ml.kg(-1).min(-1)] qualified as subjects. The training intervention consisted of a 100% increase in the habitual distance run [12 (3) miles.week(-1)] for 2 consecutive weeks, while maintaining the customary training intensity. Blood samples were obtained at rest and after maximal exercise tests, at the beginning and end of a control week of habitual jogging (baseline) and also following the 1st and 2nd weeks of the intervention. The and treadmill exercise endurance time were unchanged across sampling times. Serum T(tot) and T(free) concentrations averaged 565 (62) and 24 (2.6) ng.dl(-1), respectively, at baseline and did not change significantly. Urinary T(tot) excretion averaged 1.5 (0.21) ng.min(-1) at baseline, and also remained unchanged during the intervention. Relative increases in T(tot) (23%) and T(free) (22%) were observed following maximal exercise compared to rest ( P