Hip Flexor Muscle Activation During Common Rehabilitation and Strength Exercises

Area of Science:

• Biomechanics and Kinesiology
• Rehabilitation Science
• Musculoskeletal Health

Background:

• The iliopsoas muscle is crucial for lumbopelvic and hip anterior stability.
• This is particularly relevant in conditions like hip dysplasia and hip micro-instability.
• Understanding iliopsoas activation during exercises is key for effective rehabilitation.

Purpose of the Study:

• To systematically review electromyography (EMG) studies on iliopsoas activation during common rehabilitation exercises.
• To establish an evidence-based progression for strengthening the iliopsoas muscle.

Main Methods:

• Systematic literature search of PubMed, CINAHL, and Embase databases.
• Inclusion of nine studies with 109 healthy adult participants (ages 20-40).
• Risk of bias assessment using the Modified Downs and Black Checklist; adherence to PROSPERO guidelines.

Main Results:

• Iliopsoas activation increases with hip flexion between 30-60°, especially during leg lowering/raising exercises.
• High activation (>60% MVIC) observed in active straight leg raises (ASLR) at ~60° hip flexion and supine hip flexion/leg lifts.
• Moderate activation (40-60% MVIC) found in mid-range ASLR (~45° hip flexion) and trunk lifts in hip flexion.

Conclusions:

• Exercises involving greater hip flexion yield higher iliopsoas activation than trunk-dominant movements.
• Iliopsoas strengthening can be progressed from closed to open kinetic chain exercises, with added external loads.
• The findings provide a framework for clinical application in iliopsoas rehabilitation programs.