Muscle growth is determined not by the hormone spike after a workout but by the steady hormonal background a person lives in between sessions. The rise in testosterone and growth hormone after a heavy set lasts tens of minutes and, in controlled studies, is linked neither to gains in mass nor to gains in strength. Muscle is built over days, and across that distance what decides is the chronic hormone level, the muscle's own sensitivity to it, sleep, how much a person eats, and the total load of life. The practical conclusion: "exercises that raise testosterone" do not exist, while sleep, sufficient calories and a sensible training volume do exist and do work.
Two people "raised testosterone", and the outcome will differ
The first does heavy squats. Twenty minutes after the set, testosterone and growth hormone in his blood are noticeably above baseline. An hour later everything is back to where it started.
The second injects testosterone from outside and keeps it high around the clock.
Formally, both "raised testosterone". The second will grow muscle; the first will grow nothing from the hormone rise itself. The difference between these two cases is the central rule of training endocrinology.
What matters is the steady level of a hormone, not a short-lived spike. The spike after a set lasts tens of minutes. Muscle is built over days. One simply does not have time to influence the other.
This does not mean hormones are unimportant. It means they matter somewhere other than where people looked for thirty years. One sentence for the client: "Hormones do not decide during the hour you are in the gym, they decide during the twenty-three hours you are not."
How the axis that produces testosterone is built
Three floors, from the top down:
- The hypothalamus releases gonadotropin-releasing hormone, in pulses rather than as a steady stream.
- The pituitary responds by releasing luteinising and follicle-stimulating hormone.
- The testes: LH makes Leydig cells produce testosterone; FSH, together with testosterone, supports sperm production in the Sertoli cells.
Feedback runs upward: high testosterone in the blood inhibits the hypothalamus and the pituitary, so the system regulates itself. This loop has two practical consequences. First, secretion is pulsatile and follows a daily rhythm, so a single blood test taken at an arbitrary hour does not characterise a person. Second, if testosterone arrives from outside, the upper floors receive the instruction "production not required" and shut down.
Inside the muscle it is not only the hormone that decides, but the receptor
Testosterone binds to the androgen receptor inside the muscle cell; the complex travels to the nucleus and changes gene activity. The result: higher protein synthesis, more satellite cells, more nuclei in the fibre. More nuclei means a higher ceiling for growth, and that effect persists long after the hormone is gone.
The detail usually skipped: what matters is not only how much hormone there is, but how many receptors. In the work of Morton and colleagues (Frontiers in Physiology, 2018), muscle gain in healthy young men was associated with androgen receptor content in the muscle itself, not with systemic hormone levels.
Free and bound: why identical numbers mean different things
In blood, most testosterone is bound to sex hormone-binding globulin and to albumin. It is mainly the free fraction that works. So two men with the same total testosterone can be in very different states if their SHBG differs. Hence the clinical rule: at borderline values, free testosterone is examined, not only total. That is a physician's rule, not a coach's.
The other players: who actually affects what
| Hormone | What the gym says about it | What is known today |
|---|---|---|
| Growth hormone and IGF-1 | "The post-workout surge builds muscle" | The systemic spike produces no growth. Local factors inside the muscle itself matter more |
| Cortisol | "It destroys muscle and must be suppressed" | It rises during every hard session, and that is a normal part of adaptation. The problem starts at chronically high levels: too little sleep, a large deficit, too much life outside the gym |
| Insulin | "Fast carbohydrates are needed right after the set" | A permissive hormone, not a building one. With sufficient daily protein, an extra surge adds nothing |
| Thyroid hormones | "They need a push to speed up metabolism" | They set metabolic rate. During a hard cut their activity falls, and that is one reason everything slows down on low calories |
| Leptin | "The hunger hormone, it has to be tricked" | A signal of energy stores. It falls during weight loss and drags appetite, mood and the reproductive axis along with it |
The studies that closed the question of the hormone spike
West and colleagues (Journal of Applied Physiology, 2010) had young men train the elbow flexors under two conditions: the arm alone, at baseline hormone levels, or the arm plus a large volume of leg work, which produced a strong hormonal rise. Over fifteen weeks, gains in arm muscle and strength did not differ between conditions.
West and Phillips (European Journal of Applied Physiology, 2012) checked this in a large cohort: no association was found between the post-exercise hormone profile and gains in mass or strength. The current summary of the topic appeared in Exercise and Sport Sciences Reviews (2024) under the title "Hormones, Hypertrophy, and Hype", and its conclusion is the same.
The practical consequence is simple: do not build a programme around "hormonal" exercises. If you want big arms, load the arms. Squats and deadlifts are needed, but for other reasons.
The other side, which must not be left unsaid
The classic study by Bhasin and colleagues (New England Journal of Medicine, 1996) divided 43 men into four groups: placebo without training, testosterone without training, placebo with training, testosterone with training. Dose: 600 mg of testosterone enanthate per week for ten weeks. The group that received testosterone and did not train at all gained more muscle mass than the group that trained honestly on placebo.
Natural hormone fluctuations after a set decide almost nothing. Pharmacological doses decide a great deal. There is no contradiction between these two statements: they are different orders of magnitude.
And the price straight away, because an honest conversation has two halves. The review by Vilar Neto and colleagues (Andrologia, 2021) collected 179 cases; the outcome was fully known in only 38, and the condition proved fully reversible in four. Recovery of gonadotropin secretion takes months, and in some people full recovery never happens. The 2026 guideline of the European Association of Urology states separately that testosterone therapy is ineffective when baseline total testosterone is above 12 nmol/l. In other words, in a man with normal testosterone, adding testosterone does not "improve health". It switches off his own production, and "fixing it later" does not work.
What Arnold did and what science says today
| The view of that era | Today |
|---|---|
| Heavy compound lifts "raise hormones" and therefore grow the whole body | The spike does not decide. Compound lifts grow what they load |
| The more strongly you feel a session, the stronger the hormonal response and the growth | Sensations are not a measure. The measure is load progression in the log from month to month |
| Recovery is the rest between sets | Recovery is sleep, food and the total load of life. The hormonal background is made at night |
| That era knew almost nothing about the price of pharmacology | Arnold himself said publicly that he used drugs in the years when it was legal and done under medical supervision, and that he does not recommend it to young athletes. Data on irreversible hypogonadism and infertility simply did not exist then; today it does |
The real levers, the ones you can move legally and effectively
- Sleep, 7 to 9 hours. Sleep restriction hits muscle protein synthesis, strength performance and injury rates. It is the most common and most often overlooked limiter of progress.
- Sufficient energy. Low energy availability is a direct hit to the reproductive axis. The 2023 International Olympic Committee consensus on Relative Energy Deficiency in Sport describes, in men, reduced libido, fewer morning erections and lower work capacity, and in women, cycle disturbances up to amenorrhoea.
- Protein 1.4 to 2.0 g per kilogram of body mass per day, at 0.25 to 0.40 g/kg per meal every 3 to 4 hours.
- Fat not below 0.5 to 1.0 g/kg per day. Staying under that minimum for long has hormonal and functional consequences.
- A sensible training volume. For hypertrophy the 2026 ACSM position names at least ten working sets per muscle group per week, while the mid-point in the data sits at around twelve. Beyond that the return fades and the cost in recovery grows.
- Body fat not at either extreme, and lower chronic stress outside the gym.
- Vitamin D deficiency. A genuinely relevant topic for our region, but it is a physician who tests and corrects it, not a coach.
Where a coach's job ends
This is not caution and not covering oneself. Selecting, prescribing and withdrawing hormone therapy is medical practice. A coach who takes it on is acting outside his qualification and, if harm results, answers personally.
What a coach does: explains the mechanism calmly, without scare tactics and without romance; describes what is observable as fact, without naming a presumed cause; refers to a physician in writing, to a general practitioner, endocrinologist, andrologist or urologist; and records both the client's request and his own answer.
What a coach never does: name drugs, doses, protocols or "post-cycle exits", or compare substances; interpret lab results, including a printout the client brings in; make a diagnosis or tell the client the presumed cause of his condition; take on supervising someone through a cycle, or hint at where to obtain the substances.
Reasons to refer to a physician rather than "add more compound lifts": loss of energy, loss of morning erections, reduced libido, absence of progress despite normal food and sleep, and in women the absence of menstruation for three consecutive cycles or more.
What is still open
An honest text has to name the limits of knowledge. It is unclear why people with the same hormone levels respond so differently to the same programme. It is unclear how far androgen receptor content in muscle can be trained. The boundary of normal in older men is disputed: the 2026 Endocrine Society statement specifically underlines the continuing uncertainty about the long-term safety of replacement therapy. High-quality prospective data on the natural course of axis recovery after steroids are withdrawn are also scarce.
Five myths and short answers to them
- "Squats raise testosterone, so they grow your arms." No. The short-lived rise is not linked to gains; this has been tested in controlled work. Arms grow from loading the arms.
- "Growth hormone after training builds muscle." No. The systemic spike does not build; what matters are local factors inside the muscle itself.
- "Cortisol destroys muscle and must be suppressed." Cortisol is part of normal adaptation. The problem is not its rise during a session but a chronically high level driven by poor sleep and stress.
- "You need fast carbohydrates right after training for the insulin." With sufficient daily protein this decides nothing. The daily total matters more than the minutes.
- "You can see low testosterone by how someone looks." The diagnosis rests on symptoms plus repeated morning blood tests, not on a glance and not on a single printout.
Test yourself in thirty seconds
Answer out loud. How does a hormone spike differ from a steady level? Describe the axis controlling testosterone, all three floors. What will you say to someone who plans to deadlift in order to grow his arms? What will you do if a client brings you a printout of blood results?
Answers: the spike lasts tens of minutes and is not linked to gains, while the steady level acts across days. Hypothalamus, pituitary, testes, with feedback running upward. Arms grow from loading the arms. We do not interpret blood results; we refer to a physician.
Where this knowledge comes from
This material is built on module M-19, "Hormones and Growth", of the 720-hour coach retraining programme standing behind which is the Bodybuilding and Fitness Federation of Uzbekistan. The sourcing rule there is strict: position stands from ACSM, NSCA and ISSN, guidelines from the Endocrine Society and the European Association of Urology, meta-analyses and systematic reviews instead of single studies, and anything disputed is called disputed.
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