The primary signal that promotes contractile protein synthesis during resistance training is the high levels of mechanical stretch across the muscle membrane.

• A. True
• B. False; the primary signal is an increase in intracellular calcium
• C. False; the primary signal is hormonal signaling
• D. False; the primary signal is neural activation

Answer: (D)

Neural activation is the initiating trigger for muscle protein synthesis during resistance training. When motor units are recruited and fire at higher rates, the muscle contracts and generates mechanical tension. That neural-driven contraction creates the mechanical stimulus the muscle fibers sense, which then activates downstream signaling pathways (like mTOR) that drive protein synthesis to support hypertrophy.

Calcium flux during contraction acts as an important messenger that supports these signaling cascades, but it’s a secondary signal that follows the neural drive and the resulting contraction. Hormonal signals and systemic factors modulate the response, but they aren’t the immediate trigger initiating the anabolic signaling. The mechanical stretch seen is a consequence of the neural-driven contraction, not the primary initiator of the synthesis process.