Staining of a skeletal muscle cross-section showing different types of muscle fiber in young mice (IMAGE) ...

Cross section of muscle cells for surface fish and cavefish from the Pachón and Tinaja caves. Muscle fibers are depicted in pink and fat deposits are in white.

Whether it’s bigger biceps, a broader back, or stronger thighs, building muscle is desirable not just for aesthetic reasons. Many fitness enthusiasts want to grow their muscles without fully ...