This is the topic nobody in the cycling world wants to talk about properly. Every bloke over 40 has heard the word testosterone thrown around, usually in the context of some dodgy supplement advert or a mate at the club who reckons he has figured it all out. But the actual science of what happens to your hormones as you age — and what it means for your cycling — rarely gets discussed in a way that is useful.
So let me lay it out. Testosterone declines at roughly 1 to 2 percent per year after about age 30. If you are 45, you might be operating with 15 to 30 percent less testosterone than you had at your peak. That affects how quickly you recover from hard sessions, how effectively your muscles repair and grow, and even how motivated you feel to get on the bike in the first place.
But testosterone is only half the picture. Cortisol — the stress hormone — is the one I think matters more for most masters cyclists. When I had Joe Friel on the podcast, he was emphatic that recovery is the ceiling for older athletes. And cortisol is a big part of why. You finish a hard interval session and your cortisol spikes. That is normal. But if you go straight from the bike into a stressful work call, skip lunch, sleep poorly, and then hit another hard session the next day — cortisol stays elevated. It becomes chronic. And chronic cortisol is catabolic. It breaks down muscle. It blunts adaptation. It makes you slower.
The good news is that the biggest levers are things you can control. Sleep is number one. Seven to eight hours of quality sleep does more for your hormonal profile than any supplement on the market. Protein intake matters — Joe Friel recommends 1.6 to 2.0 g/kg/day for masters athletes, and the research supports that. Strength training twice a week stimulates testosterone production and preserves the muscle mass that endurance training alone tends to erode after 40.
Training load management ties it all together. You cannot train like you did at 30 and expect your 45-year-old body to recover the same way. That is not a limitation — it is information. Use it. Spread your hard sessions further apart. Protect your easy days. And stop treating rest as laziness.
Get a blood panel done at least once a year. Total and free testosterone, cortisol, thyroid function, DHEA-S. Know your numbers. If they come back low and lifestyle changes are not moving them, see an endocrinologist. Do not buy testosterone boosters off Instagram.
You are not done yet. But you do need to train smarter than you did 15 years ago.
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