Conventional deadlifts hit your hamstrings harder than sumo. The split is clean, repeated everywhere from programming guides to YouTube breakdowns, and the logic checks out: a narrower stance deepens the hip hinge, a deeper hip hinge demands more from the posterior chain. Everyone agrees.
This is the study that most fitness content ultimately traces its stance-targeting claims back to. It does not say what those claims assert.
Except the study that agreement traces back to didn’t find a hamstring difference at all.
Does Sumo or Conventional Deadlift Work Hamstrings More?
Conventional deadlifts produce higher lateral hamstring activation than sumo — 78% versus 71% of maximum voluntary contraction in a 2025 study of 30 experienced lifters — but the most-cited EMG comparison of both stances found no significant hamstring difference at all, and the positive result measured only one of three hamstring muscles.
— Hanen et al. 2025 · Frontiers in Bioengineering and Biotechnology · n=30; Escamilla et al. 2002 · Medicine & Science in Sports & Exercise · n=13
The most-cited muscle-activation comparison of sumo and conventional deadlifts measured sixteen muscles, including both the lateral and medial hamstrings, and measured no meaningful hamstring difference between the two stances.
A larger and more recent comparison did find a difference. Thirty experienced lifters pulled at 85% of their one-rep max in both stances while researchers recorded activation from nine muscle groups. Conventional activated the biceps femoris at 78% of maximum versus 71% for sumo, a difference that reached statistically significant in both phases of the lift.
But that seven-percentage-point margin comes with a caveat the internet ignores: only one of three hamstring muscles was measured. The 2025 study placed electrodes on the biceps femoris alone. The semitendinosus and semimembranosus — the two muscles that make up the medial hamstrings — went untested. The older study measured both lateral and medial hamstrings and found no difference in either.
The physics behind the lean toward conventional is real. A narrower stance positions the hips in deeper flexion at the start, which demands a larger hip extension effort to stand the bar up. The greater demand loads the posterior chain, and conventional produced roughly 10% higher hip extension forces than sumo in the newer study. The biomechanical logic the internet repeats is sound. The size of its practical effect is what everyone overstates.
Where the posterior chain narrative breaks down is the glutes. Gluteus maximus activation was statistically identical between stances — despite the hamstring gap and despite the higher hip extension demands in conventional. The clean “conventional equals posterior chain” framework holds for the quads (sumo was significantly higher) and partially for one hamstring muscle, but the biggest muscle in the posterior chain treated both stances the same.
Stance choice has a real but modest effect on hamstring activation — measured in one muscle and contradicted by the foundational study in the field. The variable is smaller than the deadlift conversation makes it sound. Which exercises you pick shapes where muscle actually grows, and that answer has more to do with the way each movement loads the joint than with stance width. If you’ve been fine-tuning your setup, what your shoes actually change about your deadlift lands in the same place: real physics, quieter practical gap.