Exercise and hormones: what really changes, and for how long

Two questions that are often mixed up

The first question is acute: what happens in the minutes and hours around a session. The second is chronic: what happens to resting levels and to the way the body responds after weeks or months of regular training.

Most headlines take an acute finding and present it as a chronic one. A rise in a hormone for half an hour after lifting is not the same as a lasting change in your hormonal profile. Keeping the two apart makes almost every claim about "hormone-boosting workouts" easier to judge.

Cortisol rises with intensity

Hill and colleagues had 12 moderately trained men exercise for 30 minutes at three intensities and compared them with rest. At 40% of maximal oxygen uptake, cortisol barely moved. At 60%, it rose by about 40%. At 80%, it rose by about 83%.

The authors attributed the rise partly to a concentration of the blood during effort and partly to genuine activation of the stress axis. Once they corrected for plasma volume and the time of day, the easy session had actually lowered circulating cortisol.

So "exercise lowers cortisol" and "exercise raises cortisol" are both true, depending on intensity. A hard session is a short, deliberate stress. An easy one is not.

What changes with regular training

The chronic picture concerns how you react to other stresses. A systematic review by Mücke and colleagues found that higher activity or fitness was linked with a smaller cortisol and heart-rate response to a laboratory social-stress test in 7 of 12 studies. Most of those studies were cross-sectional, so they show an association, not proof that training caused the calmer response.

That is still a meaningful pattern for someone whose job is a series of social stress tests. The practical side, adjusting training on heavy weeks, is covered in exercise and stress.

Adrenaline and noradrenaline

The catecholamines are the fastest-acting hormones in exercise. Kraemer and Ratamess describe their acute rise as critical for producing force and releasing energy during resistance exercise. The review gives no figures, and we do not quote any.

These are the same hormones involved in the alertness you feel before a pitch. That shared chemistry is one reason a very hard session late in the evening can leave you wired, and one reason a moderate session before a meeting is a better choice than an all-out one. See exercise and decision-making.

Testosterone and growth hormone: the peak that does not build muscle

After resistance exercise with an adequate stimulus, testosterone and growth hormone stay raised for 15 to 30 minutes. According to Kraemer and Ratamess, the largest acute rises come from sessions with high volume, moderate to high loads, short rests and large muscle groups. Those same sessions also raise cortisol.

Over the longer term, many studies have found no significant change in resting hormone levels with resistance training, even while strength and muscle size increased.

West and colleagues tested whether the acute peak matters. Twelve young men trained one arm under conditions that produced a large hormone rise and the other arm under conditions that produced a small one, for 15 weeks. Muscle size grew by 10% in the first arm and by 12% in the second, with no difference in strength either. The temporary hormone peak did not enhance the result.

The conclusion for programme design is simple. Choose exercises, loads and rest for the progress they bring, not for a hormone response. See strength training for executives.

Endorphins, or something else

The "runner's high" is usually credited to endorphins. Siebers and colleagues tested this in 63 people. A 45-minute run at moderate intensity raised the endocannabinoids anandamide and 2-AG. When opioid receptors were blocked with naltrexone, the runners still felt euphoric and less anxious.

The mood lift after exercise is real. Its chemistry is less tidy than the endorphin story suggests, and endocannabinoids seem to play a part.

When training outruns recovery

Overtraining syndrome is described by Meeusen and colleagues as a "prolonged maladaptation" of biological, neurochemical and hormonal regulation. Their consensus statement found that no single marker, hormonal or otherwise, meets all the criteria needed to diagnose it.

In other words, a blood or saliva test cannot tell you that you are overtrained. Persistent fatigue, falling performance and poor sleep, set against your training load, tell you more. Watching your morning pulse is one simple signal: see resting heart rate and recovery after training.

Measuring load without a laboratory

Carl Foster's session-RPE method gives a practical alternative. After each session, rate its overall effort on a 0 to 10 scale and multiply by its length in minutes. Foster and colleagues compared this with a heart-rate method across steady, interval and team-sport sessions and judged it a valid way to quantify training.

The World Health Organization's guidelines help with the rating: moderate activity is usually a 5 or 6 on a 0 to 10 scale, and vigorous activity a 7 or 8.

Take an example. Four sessions a week of 45 minutes at an effort of 6 give 270 units per session and 1,080 units for the week. The figure is in arbitrary units. It is useful for following your own trend from week to week, not for comparing yourself with anyone else, and we know of no verified "normal" weekly total or "safe" weekly increase to give you.

A week that respects the job

• Put the hardest session on a day without a critical meeting the next morning.
• In a week of closings or long-haul flights, keep the sessions and lower the effort rating rather than cancelling.
• Keep at least one easy session in the week, at an effort of 3 or 4.
• If the weekly total climbs while sleep and mood fall, reduce the load before you push further.

The sources above concern mostly men, and none of them address testosterone in women or around menopause; we make no claims on either. For training questions specific to women, see women executives and training.

Persistent fatigue, low libido, mood changes or unexplained weight change have many medical causes. See a doctor rather than self-diagnosing a "hormone" problem, and never use testosterone or other hormones without medical supervision.

If you want someone to read your weekly load with you, a Club coach can do that; you can create your space here.