If you only do part of a movement but stretch the muscle more during that part, you might grow more than doing the full movement if the full movement doesn’t stretch the muscle much.
Scientific Claim
When comparing full range of motion to lengthened partials, observed hypertrophy differences may be confounded by differences in peak resistance location, making it difficult to isolate the effect of muscle length alone.
Original Statement
“Although I do believe this is the best way to think about the current literature we have on longer versus shorter muscle lengths, I should make it clear that the categories are not always completely independent of one another. In fact, I suspect some confusion stems from this. So let me address this. Take this paper by Petrosa and colleagues which belongs to the range of motion category. It involves a comparison between a full range of motion and lengthened partial on the leg extension in previously untrained individuals finding overall more growth with the lengthened partials. Leg extensions tend to be hardest at the top. So the full range of motion likely experienced peak difficulty at this shortened muscle length whereas the lengthened partials likely experienced peak difficulty at their end point which was still at a longer muscle length. Thus both range of motion and location of peak difficulty were different between conditions.”
Context Details
Domain
exercise
Population
human
Subject
comparison of full ROM and lengthened partials
Action
may be confounded by
Target
differences in peak resistance location
Intervention Details
Evidence from Studies
Supporting (4)
The study found that lifting weights through a partial range (stretched position) and a full range led to the same muscle growth, even though the resistance felt different at the top or bottom. This supports the idea that it’s hard to tell if muscle length or where the weight feels heaviest is what really causes growth.
Muscle hypertrophy from partial repetition at long vs. short muscle length: A systematic review and meta-analysis
This study looked at whether doing partial lifts with muscles stretched (long length) vs. shortened (short length) makes muscles grow differently — and it found that muscle length itself matters, not just where the weight feels heaviest. So yes, it supports the idea that peak resistance isn't the only thing causing growth differences.
Which ROMs Lead to Rome? A Systematic Review of the Effects of Range of Motion on Muscle Hypertrophy
The study found that where you stop or start your exercise matters more than just how far you stretch the muscle — meaning the point of highest resistance, not just muscle length, might be what’s really causing muscle growth.
The study says that when you train with a full range of motion, you might see more muscle growth—but that’s probably because the weights feel heavier at the stretched position, not just because the muscle is longer. So it’s hard to tell if length or resistance is the real reason.