Motor units are recruited for force production in order according to their recruitment thresholds and firing rates. What is this principle called?

Motor units are recruited for force production in order according to their recruitment thresholds and firing rates. What is this principle called?

• A. Henneman's Rule
• B. Size Principle Of Motor Units
• C. Recruitment Order Principle
• D. Threshold Activation Rule

Answer: (B)

Size Principle Of Motor Units describes how motor units are recruited in order of their activation thresholds: small, low-threshold units are activated first, and as force demands rise, larger, higher-threshold units are recruited. The firing rates of active units also increase with increasing drive, further modulating force. This arrangement allows precise, fatigue-resistant control at low loads and progressively greater force as needed without abrupt changes in effort. It’s the standard term for this orderly, threshold-based recruitment (often linked to Henneman’s work).

Size Principle Of Motor Units describes how motor units are recruited in order of their activation thresholds: small, low-threshold units are activated first, and as force demands rise, larger, higher-threshold units are recruited. The firing rates of active units also increase with increasing drive, further modulating force. This arrangement allows precise, fatigue-resistant control at low loads and progressively greater force as needed without abrupt changes in effort. It’s the standard term for this orderly, threshold-based recruitment (often linked to Henneman’s work).