Changing the hip angle during leg extensions does not change how much the vastus lateralis muscle grows in untrained young men, meaning joint position does not selectively target one part of the...

We analyzed the available evidence on hip flexion angle during leg extensions and its effect on vastus lateralis growth in untrained young men. What we’ve found so far is that changing the hip angle does not appear to influence how much the vastus lateralis muscle grows, suggesting that joint position doesn’t selectively target one part of the quadriceps over others [1]. This conclusion is based on 60.0 supporting assertions and no refuting evidence in our current review. The vastus lateralis is one of the four muscles that make up the quadriceps group, located on the outer side of the thigh. Leg extensions are a common isolation exercise used to target these muscles. Some people assume that adjusting hip position — like sitting more upright versus leaning back — might shift the focus to different parts of the quadriceps. But according to the evidence we’ve reviewed, that doesn’t seem to be the case for untrained young men. Whether the hip is flexed at a shallow or deeper angle, the muscle growth response in the vastus lateralis remains similar. It’s important to note that this analysis only includes data from untrained young men. We don’t yet have enough information to say whether the same applies to trained individuals, older adults, or women. Also, while muscle growth may not differ, other factors like joint stress or perceived effort could still change with hip position — but those weren’t measured in the evidence we reviewed. So far, the pattern suggests that if your goal is to grow the vastus lateralis through leg extensions, you can choose a hip angle that feels most comfortable or sustainable. There’s no clear advantage to one position over another for muscle growth in this group.