Influencers call sprinting the ultimate fat-burning workout. Experts say it’s more nuanced—but research shows this high-intensity exercise offers surprising benefits for the heart, muscles, and even ...

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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 ...