Tsukuba, Japan—Muscle fibers, which constitute skeletal muscle, are classified into two main types: slow-twitch (Type I, red muscle) and fast-twitch (Type II, white muscle). Slow-twitch fibers are ...

Muscle fatigue is a condition that reduces the ability of muscle to perform over time. While it is more commonly associated with exercise, it can also result from certain medications or underlying ...

The smoking gun, for me, is the hill sprint at the end of the workout. I can still keep up with some of my younger training partners in tempo runs and mile reps, but when it comes to blasting uphill, ...