Training legs does cause a short-term spike in testosterone, but it’s smaller and shorter-lived than most gym culture suggests. A heavy leg session can raise testosterone levels by roughly 15 to 20 percent immediately after exercise, but those levels return to baseline within about an hour. More importantly, this temporary bump doesn’t appear to drive meaningful muscle growth on its own.
The Acute Spike Is Real but Brief
When you perform heavy compound leg exercises like squats or leg presses, your body releases a burst of testosterone into the bloodstream. One study measuring responses to leg press sets taken to failure found testosterone rose by about 3.8 nmol/L immediately post-exercise, a statistically significant jump. But the concentration dropped back to pre-exercise levels within 60 minutes of finishing the workout.
This pattern holds across age groups. Research comparing young men (20 to 26), middle-aged men (38 to 53), and older men (59 to 72) found that all three groups experienced a similar relative increase in both total and free testosterone after a bout of heavy resistance exercise. Older men had lower absolute levels to begin with, but their bodies still produced the same proportional spike.
It Doesn’t Raise Your Baseline Over Time
The more important question for most people is whether consistently training legs raises your resting testosterone levels, the number you’d see on a blood test taken on a rest day. The answer, based on current evidence, is no. A systematic review and meta-analysis published in Frontiers in Physiology pooled data from multiple resistance training studies and found essentially zero effect on basal testosterone. The overall effect size was -0.003, which is as close to nothing as research gets.
This contradicts a widespread belief in fitness communities that years of heavy squatting will permanently elevate your hormonal profile. The researchers noted directly that “there is a pervasive belief that resistance exercise increases basal testosterone over time,” but their analysis didn’t support it. They suggested that for people with testosterone already in the normal physiological range, changes in baseline levels may not even be necessary for muscle adaptation to occur.
Free-Weight Squats Produce a Bigger Response
Not all leg exercises produce the same hormonal response. Free-weight squats generate a greater acute release of testosterone and growth hormone compared to machine-based exercises like the leg press. This likely comes down to the greater total muscle recruitment and stabilization demands of squatting with a barbell on your back. Free-weight movements also cause more muscle damage and inflammation, which triggers a larger systemic hormonal response.
The training style matters too. Protocols using moderate intensity (around 65 to 85 percent of your one-rep max), higher volume (3 to 5 sets of 10 to 15 reps), and shorter rest periods (60 to 90 seconds) produce the largest testosterone spikes. In one study, a hypertrophy-style protocol at 70 percent of one-rep max with 60-second rest periods raised total testosterone from 7.3 to 8.9 ng/mL and kept it elevated for 30 minutes. A strength protocol at 85 percent of one-rep max with the same rest periods produced a smaller and less sustained increase, even when total training volume was equated.
So if maximizing the acute hormone response is your goal, higher-rep leg work with short rest beats heavy triples with long breaks between sets.
The Hormone Spike Doesn’t Drive Muscle Growth
Here’s where the practical significance falls apart. The idea that a post-leg-day testosterone surge helps you build muscle, especially in other body parts like your arms or chest, has been a staple of gym advice for decades. Train legs to grow your upper body, the theory goes. But a comprehensive review in Exercise and Sport Sciences Reviews concluded that this mechanism simply doesn’t work the way people think.
The researchers stated plainly that acute post-exercise rises in testosterone, growth hormone, and IGF-1 are “neither sufficient nor necessary” for stimulating muscle protein synthesis, gaining lean mass, increasing strength, or maximizing hypertrophy. In one telling finding, significant muscle fiber growth occurred in a trained leg (22 percent increase in one fiber type, 13 percent in another) despite no measurable changes in systemic hormone concentrations. Meanwhile, the untrained leg showed no growth at all, even though it was bathed in the same circulating hormones.
This is strong evidence that muscle grows because of the local mechanical stimulus, the tension and damage from actually lifting, not because of a hormonal bath from somewhere else in your body. Training legs won’t make your biceps bigger through testosterone.
Cortisol Rises Too
Testosterone doesn’t rise in isolation after a leg workout. Cortisol, a stress hormone that can promote muscle breakdown, also increases. Leg press sessions actually produced significantly higher cortisol responses compared to upper body pressing in one study, with a large effect size. This means the hormonal picture after leg day isn’t purely anabolic. Your body is mounting a stress response alongside the testosterone release, and the net effect on muscle building from hormones alone is likely close to neutral.
After particularly intense sessions, testosterone can remain somewhat elevated for up to 48 hours, but this has been observed specifically with moderate-intensity, high-volume protocols with short rest periods. For most people doing a standard leg workout, the hormonal window is much shorter.
Why You Should Still Train Legs
None of this means you should skip leg day. The reasons to train your lower body are well established and have nothing to do with testosterone. Squats, deadlifts, lunges, and leg presses build the largest muscles in your body, improve athletic performance, protect your knees and hips as you age, increase your overall calorie burn, and contribute to balanced strength that reduces injury risk.
The testosterone argument was always a secondary justification layered on top of these more fundamental benefits. Now that the science has caught up, the case for leg training is actually simpler: you train legs because legs need training, not because they’re a hormonal shortcut to building your whole body. The muscles you want to grow need to be the muscles you actually load.