Probably because of relatively weak thigh muscles and a lack of foot support.

可能是由于相对羸弱的大腿肌肉以及缺乏脚的支撑。

youdao

The piriformis muscles, strong external rotators of the thigh, attach to the sacrum and the femur. Stretching them can increase S-I joint instability.

梨状肌是附着在骶骨和大腿骨上的强大的回旋肌，对他们的拉伸有损于骶髂关节的稳定性。

youdao

For many of us, though, the thigh cannot turn out that much, either because of its bone structure or because tight muscles and ligaments inhibit its movement.

但是对大部分人来说，受骨骼结构和肌肉韧带牵制的影响，我们的大腿旋转不了那么多。

youdao

One of Volz's quadriceps muscles, or thigh muscles, is about 30% weaker on one side than the other, Hewett says.

CNN: Keeping the world's Kevin Wares injury-free

He was sweating heavily and his thigh muscles were twitchy from the steepness of the climb.

NPR: Robert Jordan, Hemingway's Bipartisan Hero

When they jump and land, athletes usually favor part of their bodies, such as the trunk, thigh muscles, knees or feet.

CNN: Keeping the world's Kevin Wares injury-free