Working your muscles while they are fully stretched builds more muscle than working them while they are shortened. This stretching advantage is especially noticeable in muscles that cross two joints, like the back of your lower leg, but doesn't seem to matter for muscles that only cross one joint.

Our current analysis shows that training muscles while they are stretched tends to build more muscle than training them while shortened. We reviewed the available research and found that 45 studies support, 0 studies refute [1]. What we have found so far suggests that the evidence we've reviewed leans toward longer muscle lengths being more effective for growth. This means that when you perform an exercise that stretches the muscle fully, you may get better results than when you only work the muscle in a shortened position. We noticed this stretching advantage is especially clear in muscles that cross two joints, which are muscles that connect to bones on both sides of a joint, like the back of your lower leg. For muscles that only cross one joint, the difference does not seem to matter as much. Our analysis is based on the evidence we have gathered up to this point, and we continue to track new research as it becomes available. If you want to apply this to your routine, try to include exercises that let your muscles stretch out fully at the bottom of each movement. For example, you might lower a weight slowly so the muscle feels a deep stretch before you push or pull it back up. Adjusting your range of motion this way could help you get the most out of your workouts.