Essentials of Strength Training and Conditioning Practice Test

When the body performs a true 1-repetition maximum, the nervous system prioritizes pulling the largest, fastest-contracting muscle fibers to generate the greatest force in the shortest time. This relies on the size principle: motor units with smaller, slower fibers are recruited first, and as demand increases, larger, faster fibers are recruited to reach peak force. For an all-out maximal effort, those high-threshold fast-twitch fibers do the heavy lifting, while the slower, more fatigue-resistant slow-twitch fibers are effectively bypassed. That’s why the slow-twitch fiber type is the one not directly contributing to the maximal lift.