Muscle atrophy is a decrease in muscle mass. upon retiring, a weight lifter who works out less will likely experience atrophy of which types of muscles?

There are two types of weight lifters: endurance weightlifters and strength weightlifters.

Endurance weightlifters use slow-twitch muscle fibers. These muscle fibers provide consistent, steady energy that allows continuous use for extended periods of time.

Strength weightlifters use fast-twitch muscle fibers. These muscle fibers contract quickly and can provide bursts of efficient energy for powerful movements. But, these muscle fibers need to be rested often because they fatigue quickly.