“Never skip leg day — training the largest muscles in your body causes a massive testosterone release that helps your entire body grow.” You’ve heard some version of this, probably from a training partner, a forum thread, or a supplement ad using it as justification for something else entirely. A real physiological observation underlies the claim. The mistake is what happens next.
QUICK ANSWER: Training large amounts of muscle mass — such as during a demanding leg workout with squats, leg presses, or deadlift variations — can produce a larger temporary rise in testosterone than smaller workouts involving less muscle mass. But the increase is short-lived and does not appear to meaningfully raise your baseline testosterone or make unrelated upper-body muscles grow faster. Leg training builds your legs extremely well; its value does not depend on turning leg day into a whole-body testosterone hack.
Why Do People Think Leg Day Boosts Testosterone?
The underlying observation is genuine. A well-cited review of hormonal responses to resistance training confirms that the size of the acute hormonal response depends on how much muscle mass is involved, training volume, intensity, rest intervals, and overall metabolic demand. A heavy squat session recruits the quads, glutes, adductors, and trunk — a large amount of total muscle mass working together. A set of biceps curls recruits comparatively little. It’s entirely reasonable that a demanding, multi-joint lower-body session produces a bigger systemic hormonal disturbance than three sets of an isolation exercise.
That’s where the fitness industry took a real observation and ran with it too far: train legs → testosterone spikes → your whole body becomes more anabolic. That leap is where this article picks up, and it shows up constantly in gym folklore, supplement marketing, and “never skip leg day” content that treats the hormonal side effect as the reason to train legs, rather than the muscle you’re building.
Does Leg Training Actually Increase Testosterone?
Yes — temporarily. This deserves a fair, precise answer rather than a flat “myth, false” dismissal, because the acute response is real and well-documented. After a sufficiently demanding resistance training session, testosterone can rise above your pre-workout baseline.
The timeline matters here, and it’s worth walking through step by step: you start at your pre-workout baseline level. During a heavy or high-volume resistance training session, that level begins climbing. It typically peaks somewhere around the end of the session or shortly after. Then, over the following hours, as your body moves into recovery, it gradually returns to baseline. By the next day, there’s no meaningful trace of that spike left in your resting hormone level. This is a normal, transient physiological event — not a lasting shift in your hormonal environment, and definitely not something that’s still “elevated” by the time you’re back in the gym 48 hours later.
Does Leg Day Boost Testosterone More Than Upper-Body Training?
This is the central question, and the honest answer isn’t simply “legs are special.” The amount of muscle mass involved and the overall training stimulus matter more than whether an exercise is classified as a “leg exercise.”
Compare three sets of biceps curls to a session of squats, Romanian deadlifts, and leg press — the second will almost certainly produce a bigger systemic hormonal disturbance. But now compare a light session of three easy sets of leg extensions to a high-volume upper-body session of bench press, rows, overhead press, and pull-ups — the “leg workout” no longer wins automatically. A 2024 randomized crossover study directly tested this by having strength-trained men perform bench press versus leg press, both taken to volitional failure at matched relative load. Testosterone rose significantly from baseline in both conditions — but there was no significant difference between the upper-body and lower-body exercise in how much it rose. When effort and volume are properly matched, “leg day” doesn’t have some special hormonal status simply for being leg day.
That nuance is worth sitting with: total stimulus and muscle mass recruited drive the response, not a body-part label.
Why the Testosterone Spike Doesn’t Mean What You Think
This might be the most important section in the entire article, because these three things get conflated constantly and they are not the same:
Acute testosterone — what happens in the hours after a single training session.
Resting/baseline testosterone — your usual, day-to-day hormonal level, measured well outside the window of an acute training response.
Pharmacologically elevated testosterone — sustained, supraphysiological hormone exposure from exogenous use, an entirely different context covered in our testosterone and muscle growth guide.
Most confusion around this topic comes from treating a temporary post-workout bump as equivalent to either of the other two.
Do Bigger Post-Workout Testosterone Spikes Mean More Muscle Growth?
This is the scientific core of the article, and it uses the same experimental logic as our growth hormone and sauna guide: researchers directly tested whether individual differences in acute hormone response predict muscle growth.
In a now-classic design, West and colleagues had young men train their arms under two different hormonal conditions — one kept testosterone, GH, and IGF-1 near baseline, while the other added heavy leg exercise immediately afterward specifically to produce a large systemic hormone spike. If the “systemic testosterone boost” model were correct, the arm exposed to the bigger hormonal spike should have shown some measurable advantage. It didn’t — the elevated-hormone condition produced no greater increase in muscle protein synthesis or hypertrophy-related signaling. A separate large cohort study tracking 56 men through 12 weeks of resistance training found no significant correlation between the size of a lifter’s acute post-exercise testosterone response and their actual gains in lean body mass or strength.
That’s the key piece of evidence this entire article rests on: the size of your testosterone spike is a poor predictor of how much muscle you’ll actually build.
Coach’s Note: I’ve never programmed squats for a client because I wanted to “boost their testosterone.” I program them when they fit the person’s goals, anatomy, training experience, and recovery capacity. If your upper body needs more growth, the solution is usually better upper-body programming — not adding exhausting leg work in the hope that a temporary hormone spike will do the job for you.
Will Training Legs Make Your Upper Body Grow Faster?
This is what bodybuilders actually want to know when they ask about leg day and testosterone. It’s rarely a purely academic question — it usually comes from someone wondering if they should tack on extra leg volume specifically to help a stubborn upper body catch up. If you squat hard on Monday and train biceps right afterward, does the testosterone released by the squat make your biceps grow more? The evidence doesn’t support that.
Upper-body muscle growth depends primarily on what you actually do to that muscle: mechanical tension, appropriate training volume, consistent progressive overload, adequate protein and energy availability, and recovery — the full mechanism covered in our muscle hypertrophy guide. None of that depends on whether you happened to squat earlier in the week hoping to “flood” your biceps with systemic testosterone. If your arms aren’t growing, the fix is almost always found in how you’re actually training your arms — volume, frequency, proximity to failure, exercise selection — not in adding more leg work as an indirect hormonal workaround.
But Doesn’t Testosterone Build Muscle?
Fair pushback, and worth addressing directly given our own testosterone article covers testosterone’s genuine anabolic role at length. Yes — testosterone absolutely matters for muscle, through androgen receptor signaling, satellite cell activity, and anti-catabolic effects covered in that guide. But a hormone being physiologically important is a different claim from every brief fluctuation in that hormone being meaningful for hypertrophy. A useful analogy: heart rate matters enormously for exercise physiology, but briefly and artificially raising your heart rate doesn’t automatically make a workout more effective. The hormone’s overall physiological role and the significance of a temporary spike in it are two separate questions.
What About Squats Specifically?
Yes, a demanding squat session can produce a genuine acute testosterone response, for the reasons covered throughout this article — it recruits a large amount of muscle mass under real load. But squats are excellent for building muscle because they provide a powerful mechanical training stimulus to the legs — not because they temporarily turn your endocrine system into a testosterone factory. That’s why you program them, not for the hormonal side effect.
Do Deadlifts Boost Testosterone?
Same story. Deadlifts recruit an enormous amount of muscle mass under heavy load, and a demanding deadlift session can produce a real acute hormonal response. But a deadlift isn’t a “natural testosterone booster” any more than a squat is — it’s an excellent, structurally demanding exercise for building the muscles it actually trains.
Does Leg Training Increase Testosterone Long Term?
Don’t expect it to. Regular resistance training carries genuine, well-documented health and body-composition benefits, but you shouldn’t expect your resting testosterone to rise substantially and permanently just because you added squats or an extra leg day. Chronic, resting hormone concentrations are shaped by a much broader set of factors — training status, age, energy availability, body composition, sleep, and overall health — not by which specific exercises populate your program. There’s no legitimate research supporting something like “two leg days a week raises resting testosterone by 20%” — that kind of precise, program-specific claim simply isn’t what this body of evidence supports. Acute response and chronic baseline are, once again, two different things, and conflating them is exactly how gym folklore turns a real short-term observation into an overstated long-term promise.
Can Hard Leg Training Ever Lower Testosterone?
This directly cuts against the “harder leg workout = bigger testosterone = better” instinct, and it’s worth knowing. Combine excessive training volume, insufficient recovery, a prolonged calorie deficit, low energy availability, and poor sleep, and the chronic hormonal picture can shift in the opposite direction. Our testosterone article covers real-world evidence of this, including a case report tracking a natural bodybuilder whose testosterone declined progressively through a demanding contest prep. For the broader picture of managing training stress before it works against you, see our guide to overtraining symptoms and prevention.
Should You Train Legs to “Optimize Your Hormones”?
No. Train legs because legs need training. Strong, muscular quads, hamstrings, glutes, and calves require progressive lower-body training — not because you’re trying to hack a temporary testosterone response. For a bodybuilder specifically, the real reasons to prioritize leg training are proportion, symmetry, total muscle mass, lower-body hypertrophy, strength, and athletic function. Those are the actual payoffs, and they don’t need a hormone story to justify them.
Common Myths
❌ Myth: Squats dramatically boost testosterone.
✅ Reality: They can produce a temporary increase after demanding training, but that’s not the same as chronically raising testosterone.
❌ Myth: Leg day makes your upper body grow faster.
✅ Reality: There’s little evidence that transient systemic hormone increases meaningfully enhance hypertrophy in muscles that weren’t directly and appropriately trained.
❌ Myth: A bigger testosterone spike means a better workout.
✅ Reality: Acute post-exercise hormone responses are poor proxies for long-term hypertrophy — studies tracking this directly have found no reliable correlation.
❌ Myth: You should structure workouts to maximize testosterone release.
✅ Reality: Structure training around effective mechanical stimulus, volume, progression, and recovery — the variables actually shown to drive muscle growth.
❌ Myth: If testosterone spikes don’t build muscle, testosterone doesn’t matter.
✅ Reality: Testosterone is genuinely important for muscle physiology — transient post-workout fluctuations are simply not equivalent to sustained hormonal exposure.
Bodybuilder’s Take
Leg day can raise testosterone. That’s the true part of the myth. The misleading part is assuming the temporary rise makes your entire body more anabolic or gives unrelated muscles an extra hypertrophy stimulus. Train legs to build your legs. Train your upper body to build your upper body. Let your endocrine system respond naturally to demanding training, rather than designing workouts around chasing a hormone spike that the evidence says isn’t doing what you think it’s doing.
