Apply the principles of training to personal fitness goals. your friend is working on lower body and has been doing one set of 8 bodyweight squats each day. give specific suggestions on how your friend can apply the principles of progression and overload to her current squat routine to see improvement in lower body strength over time.

The principles of training are three: Overload, Specificity and Progression.

Overload refers to working out with a greater amount of weight, more than normal. This way, the person will develop muscle strength, because he is pushing out of his limits.

Progression refers to the increase of weight progressively, this way the improvement won't stop.

In this example, my friend should increase the weight near his limit (just near), but that amount of weight should allow him to do at least three series (he first needs to try different weights to know his limits). So, to preserve safety, I will say 3 set of 5 repetitions, with heavy weight just below his limit.

Then, I would recommend and tiny increase in each set. So, each new set must have an 10 pounds extra, this way my friend will be constantly improving. In no time, he will be breaking his limits, and reaching new weights, which also will improve the muscle strength.