• Energetics of Muscular Contraction:
• Skeletal muscle converts chemical potential energy stored in ATP into mechanical work ($W = F \times d$) and heat ($Q$):

• Under optimal biomechanical load and steady-state contraction, the maximum thermodynamic mechanical efficiency of skeletal muscle contraction is $\approx 20 - 25\%$ (typically 20%).
• The remaining $75 - 80\%$ of total chemical energy is liberated as thermal energy (heat of activation, maintenance, and shortening), which is essential for mammalian homeothermic thermoregulation.
• nalysis:
• (20%): Correct physiological efficiency value.

Correct option: (2) 20%