Actually, just let nature take its course. Use the most comfortable and natural posture.
The last lap is a professional sprinter. The amateur's cardiopulmonary skills are not enough, so just run down. It is dangerous to sprint hard at the end.
And when you train to that extent, you will naturally know how to sprint.
About how to run:
Breathe rhythmically and you'd better follow your footsteps. Two steps, one call, three steps, one call, three steps, two calls, etc ... which one is comfortable to use. Don't mess up the rhythm. If it is chaotic, it is easy to get angry.
When running, your upper body should be straight and lean forward slightly. Your arms swing naturally (up to your chest and down to your waist).
The lower body runs naturally. Pay attention to the fact that it is best to land your feet with your front and back palms at the same time (if you don't pay attention, you will get used to using them first and then landing with your palms, which will hurt your knees).
Correct an error in 1 building. It is impossible to thicken your legs in long-distance running. If you want to thicken your legs and build large muscles, you must pass special strength training.