Assessing muscle performance is vital for patients recovering from foot and ankle injuries, especially for those returning to athletic and recreational activities. The ankle muscles, particularly the plantar flexors, are key contributors to sport performance, aiding in rapid acceleration during sprinting, cutting, and jumping. They also play a critical role in eccentrically working upon landing, jumping, and cutting. It's emphasized that assuming a rigid foot model, which overestimates ankle power, is an oversimplification. The ability of foot structures to resist deformation is equally important as ankle plantar flexor power for efficient power transfer during push-off. Without the foot system's capacity to transfer power into the ground, technique, mechanical effectiveness, and ultimately, acceleration performance can degrade.

Operational Definitions of Muscle Performance Constructs: To provide a comprehensive assessment, muscle performance is broken down into several constructs:

• Motor Coordination: The ability to move multiple body parts in a coordinated, effective, and efficient manner. This can be assessed qualitatively or quantitatively.

• Muscle Endurance: The ability to maintain a specific percentage of maximal voluntary contraction over a period of time, often quantified by total work or number of repetitions, and can include a fatigue index.

• Muscle Strength: The maximal force a muscle or muscle group can generate, typically measured in Newtons or pounds.

• Muscle Power: The maximal force a muscle or muscle group can generate over a given unit of time, quantified as force multiplied by velocity (e.g., Watts or Joules per second).

• Muscle Reactive Strength: The ability to quickly transition from an eccentric to a concentric contraction, quantified using reactive strength indices, often involving jump height and contact times.

The Muscle Performance module provides a structured, evidence-based approach to comprehensively evaluate a patient's muscular capabilities from the intrinsic foot muscles to the entire lower kinetic chain, guiding clinicians in making informed return-to-activity decisions.