During which stage of sleep, also known as delta sleep, would a person have slow breathing and be difficult to wake.

in stage 3 of non-rapid-eye-movement sleep

Explanation:

this is the answer for plato

the gravitational force on an object increase as the mass of an object also, im not going to report you, but this question should be under the science category, not health

take a break move to stretching and slowly work back into physically exercising if the problem continues go to a doctor or physical therapist