If women who don't usually work out do leg exercises through only part of the movement, they get stronger in just that part of the motion — and it doesn't help much with the rest of the movement.

What we've found so far is that partial range of motion exercises appear to improve strength mainly in the specific part of the movement that is trained, at least for women who are not regular exercisers doing knee extensions [1]. Our analysis of the available research shows the evidence leans toward this effect being limited to the trained range. We looked at 37.0 assertions from studies and found consistent support for the idea that when untrained women perform knee extension exercises through only a portion of the full movement, strength gains occur in that portion [1]. However, those improvements do not seem to carry over strongly to other parts of the motion. This suggests that the benefits of training in a partial range may not extend well beyond the angles or positions that were actively worked. Our current analysis shows no studies that refute this pattern, but we are still building our understanding. Since all the supporting evidence comes from the same body of assertions, we can't yet say how strong or broad this effect might be across different people or training programs. We also don’t have enough data to determine whether combining partial and full range training might lead to better overall results. It’s important to remember that this conclusion is based only on what we’ve reviewed so far. As more evidence becomes available, our understanding could change. Practical takeaway: If you're new to strength training and only work your legs through a short part of a knee extension, you’ll likely get stronger in that exact spot — but don’t expect much improvement in other parts of the movement.