Please help
Nerves and cells in your body need to live.

Blood and oxygen I’m pretty sure if it’s one answer then it should be blood

People who utilizes the progression principle will ensure their exercise program increases in frequency, intensity, time, and type. the changes need to happen gradually in order to ensure they make gains in their fitness program. a person who doesn't utilize the progression principle can still gain health benefits from exercising, but will not continue to improve in cardiovascular fitness.

Peptic ulcer;