Essentials: How to Exercise for Strength Gains & Hormone Optimization | Dr. Duncan French

Andrew Huberman opens this Essentials episode by introducing himself as a Stanford professor of neurobiology and ophthalmology, then reintroduces his guest, Dr. Duncan French, at the UFC Performance Institute. Huberman says he found dozens of papers on how weight training affects hormones with French's name on them. His first question is about mechanism: what about engaging motor neurons under heavy loads tells the endocrine system to release testosterone? He says he has never found the answer in a textbook.

French frames it as a stress response, with both a mechanical and a metabolic part. He notes that testosterone release at the gonads is regulated by many different areas, and says his own work focused on catecholamines and sympathetic arousal: epinephrine (adrenaline) and noradrenaline. He studied how they signal through the HPA axis to release cortisol, and how that cascade also acts on the adrenal medulla to release androgens before the signal reaches the gonads.

I think it's the stress response, right? It's mechanical stress and it's metabolic stress.

Huberman asks whether weight training raises testosterone in women, who lack testes. French says yes, and describes the adrenal glands as the only site of testosterone release in females, through the same downstream cascade. He adds that the effect is much smaller in females, but says there is good data showing that women can use resistance training as a stressor to raise their "internal anabolic milieu." That can then drive muscle growth along with tendon and ligament adaptations.

When Huberman asks whether the testosterone men produce during training comes from the adrenals or the testes, French says the field is "divided presently." One view centers on the acute adrenergic response to a stress-driven stimulus, which might come partly from the adrenal glands and partly from the gonads. The other centers on long-term exposure to an anabolic environment, which he says is primarily driven by the gonads. The open question, in his words, is whether hypertrophy comes from the acute, largely adrenal responses or from "elevated basal levels" of habitual testosterone.

The two then widen the view beyond muscle. French notes that androgen receptors sit on neural tissue and neural axons, and Huberman calls them "pretty much everywhere." French lists ligaments, tendons and, "to some extent," bone as tissues testosterone can influence. He says it could help counter osteopenic characteristics, and calls it "a magic hormone, let's say, with many end impacts in terms of adaptation." He speaks of potential and offers no specific bone data.

Huberman asks for general training principles that favor testosterone, aimed at non-elite people who want to build or keep muscle, change body composition, or stay strong for other sports. French draws a line between two hormones. He says testosterone responds to both an intensity factor and a volume factor, while growth hormone is "largely driven by an intensity factor alone."