Final answer:
Fatigued muscle cells that recover rapidly are typically the result of slow exercise of long duration, involving the use of slow-twitch muscle fibers that are suited for endurance and efficient oxygen utilization.
Step-by-step explanation:
Saved fatigued muscle cells that recover rapidly are the products of slow exercise of long duration. This type of exercise predominantly utilizes slow-twitch muscle fibers, which are adapted for aerobic activities such as long-distance running and maintain contractions over long periods. Slow-twitch fibers have a high number of mitochondria and myoglobin, enabling them to efficiently use oxygen for ATP production during extended periods of endurance exercise, thus allowing for quick recovery from fatigue.