Im new here, I have a question about a Job and the 400m.

I am looking for a field to go into in college about sports science. Like Sports Biomechanics, or something to do with how the body works and how to enhance performance. For example; whenever scientists have surveys posted on the internet that proves that drinking coffee can enhance a person's performance by the caffeine. What is that Job? Thank you!

Also, If you a 400m runner who runs a 58.13 and has the speed for the race but lacks the endurance at the last 100m how do you improve that area without hitting a wall? Im good til the last 100m, Im going ffast then the last 100m feels like im running 14-15 seconds. If I didn't hit a wall, I could run about 53-54 but idk how to improve that area.