College of Massage Therapists of British Columbia (CMTBC) Practice Exam

What type of muscle fibers would be more prevalent in a bodybuilder's muscles?

1. Slow-twitch fibers

2. Fast-twitch fibers

3. Intermediate fibers

4. All muscle fibers equally

The correct answer is: Fast-twitch fibers

The prevalence of fast-twitch fibers in a bodybuilder's muscles is directly linked to the specific demands of bodybuilding, which typically involves heavy resistance training and explosive movements. Fast-twitch fibers, or Type II fibers, are designed for short bursts of power and strength, allowing athletes to lift heavy weights and perform intense exercises. These fibers are more capable of generating greater force and facilitating muscle growth due to their ability to adapt to high-resistance training by increasing in size – a process known as hypertrophy. In contrast, slow-twitch fibers, or Type I fibers, are primarily utilized for endurance activities, permitting sustained muscular contractions over longer periods. While they play an important role in overall muscle function and stamina, they are not the predominant type found in individuals focused on maximizing muscle strength and size, such as bodybuilders. Intermediate fibers, or Type IIa fibers, possess characteristics of both slow-twitch and fast-twitch fibers, but they do not reach the level of specialization for explosive strength that fast-twitch fibers do. Although all muscle fibers are present in the human body, the training regimens of bodybuilders emphasize the recruitment and development of fast-twitch fibers, leading to their predominance in their muscle composition. This means that for a bodybuilder