脚力

leg strength

脚力

my leg strength

have strong legs

脚力がある

strength   /streŋkθ/　noun   力･強さ･体力

★ the quality of being physically strong

lose one's walking ability

arm strength　腕力

If you believe that you don't have strong legs, I suggest that you run a lot of middle distance races like half marathons or long slow distance in order to get strong legs. I'm in the same boat.