Muscle Cross-Bridge Cycle

Huxley sliding filament model — actin-myosin force generation

ATP Rate (kcat)8

Ca²⁺ Activation70%

Load Force30%

Head Stiffness5

Huxley (1957) cross-bridge model: myosin heads attach to actin binding sites (rate f), generate force by pivoting (power stroke ~11nm), detach (rate g). ATP hydrolysis resets the head. Ca²⁺ exposes binding sites via troponin-tropomyosin complex. Force-velocity relation: F(v) = F₀(1−v/v_max) (Hill equation).