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Peak physique with low testosterone
He was exercising roughly 26 hours a week, swimming and cycling hard and lifting hard, and was grossly overtrained. His testosterone was in the toilet, yet he looked like twice the man he is today. His testosterone now is probably twice as high as it was then, and it has fluctuated quite a bit across his life.
What testosterone offers is the ability to do more work, recover more from workouts, and build muscle through protein synthesis. Given to someone who sits on the couch with no change in nutrition or exercise, it does little. On its own it probably helps with insulin resistance, which leaves most of what it can offer unused.
How does overtraining lower testosterone?
Heavy training with too little recovery or food can dampen the brain's signal to the testes. The hypothalamus releases gonadotropin-releasing hormone in smaller pulses, which lowers luteinizing hormone and, in turn, testosterone. The physiologist Anthony Hackney has described this as the exercise-hypogonadal male condition in endurance athletes. In his reviews, resting testosterone was lower in many endurance athletes than in sedentary men.
How does testosterone build muscle?
Testosterone binds androgen receptors inside muscle cells and switches on genes that increase protein synthesis. It also increases the number of satellite cells, the stem cells that donate nuclei to growing muscle fibers. In a 2003 study led by Indrani Sinha-Hikim, men given graded amounts of testosterone showed increases in muscle fiber size and in the number of satellite cells.
Is there a natural ceiling for muscularity?
In 1995, Kouri and colleagues published a study in the Clinical Journal of Sport Medicine comparing fat-free mass index in 157 male athletes, some who admitted using anabolic steroids and some who did not. No non-users exceeded an index of about 25, and the authors proposed it as a rough natural limit. Critics have pointed out that steroid use in the sample was self-reported.
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