The benefits of regular HIIT go well beyond its effect on muscles. Among other payoffs, HIIT increases the heart’s ability to pump blood efficiently by making its chambers larger and more elastic. HIIT also augments the number, size, and elasticity of arteries and increases the number of tiny capillaries that infuse muscles. HIIT further improves muscles’ ability to transport glucose from the bloodstream and increases the number of mitochondria within each muscle, thus supplying more energy.54 These and other adaptations lower blood pressure and help prevent heart disease, diabetes, and more.
