I try improving my running by strengthening my legs. my back, any muscle I use. The one exercise the does the most is focusing on my core. And no matter how hard I try I will never be as good as someone else. The only thing that truly matters is being the best I can be. My core strength affects every aspect of me. Everyone has different abilities but everyone is able to be as strong as they were intended to be.
God is the only real strengthener of your core. The activities humans do on their own with legs, and arms, and mind, and will, and emotion, are amazing. But when the maker of your soul is not the one radiating strength we still are not being what we were intended to be,
Ephesians 3:16 That He would grant you according to the riches of His glory, to be strengthened with might in the inner man