Six weeks of conditioning exercise increases total, but not free testosterone in lifelong sedentary aging men

IntroductionAdvancing age is associated with a gradual decline in circulating androgens, and the putative role of exercise training on systemic androgens remains to be adequately defined. 
MethodsThe present investigation examined the impact of 6 weeks of supervised exercise training on resting levels of systemic hormones in a cohort of lifelong sedentary men [ SED ( n = 28), 62.5 +/- 5.3 years], compared with a positive control group of age- matched lifelong exercisers [ LE ( n = 20), 60.4 +/- 4.7 years, 430 years training history]. Blood hormones were sampled pre- and post- intervention from an antecubital forearm vein and analysed using electrochemiluminescent immunoassay. Cardiorespiratory fitness (VO2peak) was determined via indirect calorimetry during an incremental cycle test to volitional exhaustion. 
ResultsAnalysis of variance ( ANOVA) revealed a lack of significant change in any parameter amongst LE, whilst SED experienced a significant exercise- induced improvement in cardiorespiratory fitness and total testosterone ( all p<0.05). Concurrent increases in sex hormonebinding globulin ( SHBG; p<0.05) resulted in a lack of change to either bioavailable or calculated free testosterone ( p>0.05) amongst SED. 
ConclusionsAlthough resting levels of systemic total testosterone increased in response to 6 weeks of exercise training, increases in SHBG negated any potential relationship between calculated- free or bioavailable testosterone. These findings indicate that increases in bioavailable testosterone fraction are not required for cardiorespiratory fitness improvements in aging men.