Novel Assessment of Isometric Hip Extensor Function: Reliability, Joint Angle Sensitivity, and Concurrent Validity.

Area of Science:

• Biomechanics and Exercise Physiology
• Musculoskeletal Function Assessment

Background:

• Closed-chain hip extension function assessment is underdeveloped.
• A standardized, reliable method is needed to evaluate isometric hip extensor strength and muscle activation.

Purpose of the Study:

• To assess the reliability, joint angle sensitivity, and concurrent validity of a novel force plate-based isometric hip extensor test (isometric hip thrust).
• To examine muscle recruitment patterns during the isometric hip thrust using surface electromyography (sEMG).

Main Methods:

• Repeatability was assessed over four sessions with 14 active men (19-29 years).
• Joint angle sensitivity of force, torque, and sEMG was evaluated at four hip flexion angles in 10 subjects.
• Concurrent validity was determined by comparing isometric hip thrust torque with isokinetic dynamometer measurements in standing and supine positions.

Main Results:

• The isometric hip thrust demonstrated good repeatability (Intraclass Correlation Coefficient [ICC] = 0.87) with minimal learning effects after familiarization.
• Increased hip flexion enhanced peak extension force and gluteus maximus activation while reducing biceps femoris activation.
• Isometric hip thrust torque showed moderate correlation with supine isokinetic dynamometry (R² = 0.555) but not with standing measurements (R² = 0.193).

Conclusions:

• The isometric hip thrust is a repeatable and valid method for assessing hip extensor function, particularly when familiarization is included.
• The test's sensitivity to joint angles allows for nuanced evaluation of force production and specific muscle recruitment (gluteus maximus, biceps femoris).
• This assessment offers a practical tool for understanding functional hip extensor capabilities and guiding training interventions.