Does It Matter Which Exercise You Pick for Muscle Growth?

Ask which exercise is better for quads and the internet splits into camps. Leg press on one side, leg extension on the other. Influencers film comparison videos. Forum threads run a thousand comments deep. The format never changes: two exercises enter, one winner emerges.

The gym's comparison format exists because people genuinely want to know. Exercise selection feels like it should have a right answer. Pick the best one, do it consistently, move on.

A meta-analysis pooling data across multiple studies tried to settle this definitively. Single-joint and multi-joint exercises produce effectively zero difference in total muscle growth. Not a small edge. Zero meaningful difference. Every comparison video that crowned a winner was arguing about nothing.

But every analysis that stopped at total growth missed what was hiding inside that equality. Burke and colleagues designed the cleanest possible test: 28 trained lifters, each training one leg with leg press and the other with leg extension, for eight weeks. They measured two of the quad's four heads, not the whole muscle. Each exercise grew a different one more.

Inside the same quad

The front of the quad — the muscle you see when someone flexes straight on — grew nearly twice as fast with extensions. 8.9% versus 4.7% with press. Across the front-quad measurement sites, the study's model put the probability that extensions grew it more at 91% to 99%.

The outer quad told the opposite story. Growth was three times faster with leg press: 8.7% versus 2.9% from extensions.

Same person. Same effort. Same eight weeks. Opposite regional results.

The within-subject design is what makes this hard to dismiss. When different people respond differently, you can blame genetics or training history. When the same person's two legs grow most in different places, those explanations vanish.

Genetics, nutrition, sleep, hormones — all identical between legs. The only variable was the exercise.

With leg press as the only quad exercise, the front quad grew roughly 53% as much as it did with extensions: 4.7% against 8.9%. Not because the leg press is bad — the outer quad grew most with it. Both exercises grew both heads, but each led in a different one. To fully develop the quad, the authors conclude, it would seem both kinds of exercise are needed.

Every muscle tells the same story

If this were only a quad finding from one lab, it would be interesting but easy to set aside. Twenty-eight people, eight weeks, one study.

Then independent research teams started reporting the same pattern — without coordinating, without building on each other's work, and in completely different muscles.

For glutes, Krause-Neto and colleagues pooled 12 studies with 318 participants and found that hip thrusts, squats, and deadlifts each grow different regions of the same muscle. The measured difference was medium-to-large — big enough that exercise choice meaningfully changes which part of the glute develops.

For chest, a 23-study meta-analysis found that bench angle changes which pectoral region gets the primary stimulus, with a large measured difference between incline and flat positions.

There’s a competing explanation that’s gained serious traction: maybe it’s not the exercise. Maybe it’s the stretch. Training at longer muscle lengths, the theory goes, is what drives regional growth. The exercise itself doesn’t matter — only where the muscle gets stretched.

A separate meta-analysis tested it across 12 studies. The regional growth effect from muscle length alone was trivially small. All effects fell within the range of practically zero. The differences are exercise-driven, not stretch-driven.

Four independent research teams. Four muscle groups. Same conclusion. A pattern too consistent to be one lab's anomaly.

Maybe it's not your genetics

Burke's team also measured calves. This finding may carry more emotional weight than anything else in the dataset.

A straight-leg toe press, done on a leg press machine with the knee straight, grew the main visible calf muscle more than seated raises did, with a 99.1% probability by the study's model. For the soleus — the muscle underneath the gastrocnemius — the result was uncertain, leaning slightly toward the seated raise.

The 99.1% is how likely it is that the straight-leg exercise grew that muscle more, not how big the difference was: the authors class the effects as relatively modest, and the calf evidence overall as weaker than the quad evidence.

The gym's most universal excuse — "calves are just genetic" — may be masking something far simpler. If your calf routine defaults to the seated machine, that was the weaker choice for the main calf muscle in this study. That is a narrower point than "the seated machine trains a different muscle": the study compared the two exercises for each calf muscle, and only the main one showed a clear difference.

Before blaming DNA, the data suggests checking the exercise.

The map

Here's what the evidence points to.

If your only quad exercise is the leg press, the front quad grew about half as much in this study as it did with extensions. Adding a single-joint exercise addresses the region the leg press grew least. The authors caution that the result may not carry over to squats, lunges or other leg press variations. This isn't about overhauling a program that works — it's about completing what one exercise leaves unfinished.

The posterior chain tells the same story — four hamstring muscles each responded to a different joint action, with the deepest of the four showing zero growth from knee-flexion alone.

If your calves frustrate you, check the exercise before anything else. The 99.1% probability makes a straight-leg calf exercise the first change worth trying; in this study it was a toe press on a leg press machine, knee straight.

The principle extends past the muscles this study directly measured. In separate triceps research, overhead extensions grew the long head at 17.5% while bench press managed just 2.1% for the same head. Same regional pattern, different muscle, different team.

For the quad, the authors conclude it would seem one exercise is not enough. For the calves, they drew the opposite lesson: the straight-leg exercise seemingly developed all three calf muscles, and whether the seated raise adds anything is unclear. So "no single exercise does the whole job" is not a rule for every muscle. Which muscles benefit most from adding the targeted work — and which are genuinely fine without it — is a question with its own cross-study data.

Where the evidence gets honest: this finding comes from trained lifters, who had lifted at least three times a week for at least a year. One study found the opposite quad pattern in beginners — the compound actually favored front-quad growth in untrained participants. But that compound was a one-leg Smith machine squat, and Burke's team suggests, as speculation, that the sample, the exercise or both could explain the difference.

Whether the regional pattern holds for beginners is not settled. The authors write that their findings cannot necessarily be generalized to untrained people, though they see no logical reason the results would differ. And for the main calf muscle, an earlier study in untrained people found what Burke's study found.

The equipment question has a simpler answer. A 2023 review of 13 studies with over a thousand participants found no significant difference in muscle growth between machines and free weights in the five studies that measured it. The exercise can change where the growth goes.