What must we do to voluntarily activate the other type of motor units?

• A. Passive stretching
• B. Active contraction and E-stim
• C. Passive rest
• D. No intervention

Answer: (B)

Motor units are recruited in a specific order when we recruit muscles voluntarily, with smaller, slow-twitch fibers typically firing first and larger, fast-twitch fibers needing a stronger drive. The “other type” of motor units—fast-twitch fibers—are often not brought in with voluntary effort alone, especially when strength is reduced or neuromuscular control is imperfect. Using active contraction together with electrical stimulation provides both the patient’s voluntary drive and an external, direct activation of motor neurons, which helps recruit those fast-twitch units that voluntary effort alone might miss. This combo tends to produce greater motor unit recruitment, stronger contractions, and better neuromuscular re-education than either approach alone. Passive stretching, rest, or doing nothing at all won’t achieve this targeted activation.