Which muscle fiber type shows the greatest increase in size comparatively?

Which muscle fiber type shows the greatest increase in size comparatively?

• A. Type I
• B. Type IIa
• C. Type II
• D. Type IIx

Answer: (C)

When muscles are overloaded with resistance training, the fast-twitch fibers show the most growth in size. These fibers have a greater capacity for increasing contractile protein and activating satellite cells in response to high-intensity stimuli, leading to larger cross-sectional areas. Type II fibers are the fast-twitch group that reliably hypertrophies more than slow-twitch fibers, which are more geared toward endurance adaptations with smaller gains in size. Among the fast-twitch options, the glycolytic, quick-to-fatigue fibers drive the largest increases in muscle cross-sectional area under typical heavy resistance training, so the overall greatest size increase is seen in the fast-twitch fiber category.

When muscles are overloaded with resistance training, the fast-twitch fibers show the most growth in size. These fibers have a greater capacity for increasing contractile protein and activating satellite cells in response to high-intensity stimuli, leading to larger cross-sectional areas. Type II fibers are the fast-twitch group that reliably hypertrophies more than slow-twitch fibers, which are more geared toward endurance adaptations with smaller gains in size. Among the fast-twitch options, the glycolytic, quick-to-fatigue fibers drive the largest increases in muscle cross-sectional area under typical heavy resistance training, so the overall greatest size increase is seen in the fast-twitch fiber category.