A static assessment has no movement but also is a movement where the distal segment is fixed.Your examining the relative movement of the fixed surface(feet) on the rest of the body.
Therefore squat is a STATIC assessment.
To clarify and what really is misunderstood in the industry about static and dynamic assessments. Static assessments are when the patient is standing still or when feet are in contact with the floor. Ie. Posture asessment vs. an inplace squat assessment.
When you are asking someone to perform a forward lunge or throwing a ball, climb stairs, this is a DYNAMIC ASSESSMENT.
It is vital for the personal trainer to understand the anatomy, functional anatomy contracting concentrically/eccentrically and biomechanics and lines of force affecting the entire kinematic chain.
To answer the question, when a client is supinating while demonstrating IR at the hip, the peroneals are eccentric lengthening, lateral gastro is concentrically shortening, at the knee, the quadriceps are concentrically contracting, the ITB is lengthening(eccentric) and glute med and min are concentrically(shortening).