Does Lifting Weights Increase Testosterone? Yes — And It Made No Difference
Yes. Lift something heavy and your testosterone goes up. It is real, it is measurable, and it has been documented for decades.
It also appears to do nothing whatsoever.
And we know that with unusual confidence, because somebody designed an experiment specifically to find out — one of the cleverest in exercise science.
They trained one man’s two arms under different hormones
In 2010, twelve young men trained their elbow flexors for fifteen weeks. Each man trained both arms, on separate days, doing the same arm exercise — but under deliberately different hormonal conditions. [1]
On one day: arm curls, and nothing else. Blood tests confirmed no rise in testosterone, growth hormone or IGF-1.
On the other day: the identical arm curls, immediately followed by a large volume of heavy leg work — squats and leg presses — purely to flood the bloodstream with hormones. That worked: significant elevations in all three, measured straight after and again at 15 and 30 minutes, and the effect held across the whole fifteen weeks. [1]
So the same arm exercise, in the same man, with the same genetics, sleep, diet and training history — the only difference being whether it was performed in a bath of anabolic hormones.
| Arm | Hormones after training | Muscle gained |
| Curls only | no rise | +12% |
| Same curls, then heavy leg work | big rise in testosterone, growth hormone and IGF-1 | +10% |
The arm that got no hormone spike grew 12%. The arm bathed in testosterone, growth hormone and IGF-1 grew 10%. The difference was not statistically significant. Strength went up in both, equally. Type I and type II fibres both grew, with, in the paper’s words, “no effect of hormone elevation”. [1]
If the post-workout hormone surge were driving muscle growth, that experiment would have found it. It is about as direct a test as you can run in a human being.
Then they did it again, bigger, in people who already lift
The obvious objection is that twelve untrained men and one arm exercise is a narrow test. So the same group ran it wider.
In 2016: 49 resistance-trained men, twelve weeks of whole-body training, with muscle biopsies, DXA scans, strength testing and hormone measurement before and after. The verdict: “No significant correlations between the acute postexercise rise in any purported anabolic hormone and the change in strength or hypertrophy were found.” [2]
Their summary sentence leaves no room: acute post-exercise hormonal rises are “not related to or in any way indicative of” the muscle and strength you gain. [2]
And in a separate cohort of 56 men, measuring hormone responses at the midpoint of a twelve-week programme: no significant correlations between growth hormone, free testosterone or IGF-1 and gains in lean mass or leg press strength. No correlations with strength at all. [3]
The funny part
In that cohort of 56, one hormone did correlate positively with gains in lean body mass and type II fibre size.
Cortisol. [3]
The hormone marketed to you as catabolic — the one whole supplement categories exist to suppress — was the one that tracked upward with growth. The correlations were weak (r = 0.29 and r = 0.35, which is to say cortisol explained under a tenth of the variation), and we are not going to build a theory on them.
That is exactly the point. They are weak, they are the wrong sign, and they are as good as anything testosterone managed. When your framework predicts one hormone matters and the data hands you a different hormone pointing the wrong way, the framework is the problem.
So what does predict who grows?
This is the part that makes the page worth reading, because the answer is not “nothing”.
In 2013 a study followed 23 men through sixteen weeks of training and measured things inside the muscle as well as in the blood. Average fibre growth was 20%, but the range ran from −7% to +80% — some men nearly doubled their fibre size and one went backwards. [4] Plenty of variation to explain.
Blood hormones explained none of it. Free testosterone, growth hormone and IGF-1 all showed “no relationship” with how much anyone grew. [4]
Three things did correlate. The change in androgen receptor content in the muscle itself (r = 0.60). The activation of p70S6K, a signalling protein that switches on muscle protein synthesis, measured five hours after training (r = 0.54). And the interleukin-6 response (r = 0.48), though the authors are candid that they do not know why.
Their conclusion: this implicates “intramuscular rather than systemic processes in mediating hypertrophy.” [4]
In plain terms: it is not how much testosterone is floating in your blood. It is how well the muscle you just trained can hear the testosterone that is already there — how many receptors it has — and what the machinery inside that muscle does in the hours afterwards. The signal is local. The blood test is looking in the wrong place.
And the spike is not even extra production
One more detail, from the study that measured this properly. Using stable isotope dilution — tracking a labelled version of the hormone to separate how fast it is made from how fast it is cleared — researchers found the post-exercise rise “appeared to be induced by decreased metabolic clearance rate of T.” [5]
Your body was not making more testosterone. It was removing it more slowly for a while. The spike is a traffic jam.
The same study also looked at what twelve months of resistance training did to testosterone metabolism overall. Answer: “No changes were observed… indicating a homeostatic stability for this hormone in men of different ages.” [5] That study had thirteen people in it, which is worth saying plainly — it is a mechanistic study, not a population one.
The verdict
Lifting does not raise your testosterone in any sense that matters. It produces a transient rise that is mostly slower clearance, that predicts nothing about how much muscle or strength you gain, and that a fifteen-week within-subject experiment showed makes no difference when you manipulate it directly. Over a year of training, resting testosterone did not move.
What lifting does is build muscle. Every single study on this page found that — 12% here, 20% there, up to 80% in one man. The mechanism just is not the one on the supplement label. It runs through receptors and signalling inside the trained muscle, not through a number in your bloodstream.
Which is quietly good news. It means the thing that determines your results is the training you did, not a hormonal lottery you were hoping to game. Nobody needs to chase a post-workout window, take a booster to amplify a spike that does nothing, or arrange their programme around a hormone response.
If you want your resting testosterone to move, the evidence points at body weight, not at the barbell. Lift because it works. Just not for that reason.
Part 6 of a series on testosterone. Earlier: whether to get tested, what normal means, what actually raises it, and whether boosters work.
Related: how to increase testosterone naturally · do testosterone boosters work · is creatine safe · normal testosterone levels by age
