Original Research

The Impact of Sagittal Plane Hip Position on Isometric Force of Hip External Rotator and Internal Rotator Muscles in Healthy Young Adults  

Authors:  Hoglund LT, Wong AL, Rickards C

Hip external rotator (ER) and internal rotator (IR) muscle weakness is theorized to be associated with lower extremity injury in athletes such as knee ligament tears and patellofemoral pain. Previous studies investigating the strength of hip musculature have utilized various sagittal plane hip positions for testing. The relationship between results at these different positions is unknown.  The authors found that hip IR normalized peak force was greater at 90° as compared to 0° flexion position bilaterally in both genders (p < .01). Hip ER normalized peak force was greater at 90° compared to 0° flexion in dominant limbs of both genders and in non-dominant limbs of males (p < .01). Non-dominant hip ER normalized force in females was greater at 90° versus 0° flexion; however, it was not significant (p = .092). Post hoc analysis of normalized average force (average over 5-second contraction) yielded similar results. Therefore, clinicians and researchers should use consistent positioning for testing of hip ER and IR strength. This will improve certainty of determining if a patient’s strength has changed or if differences between groups are present. Reference values reported will be useful in order to determine if weakness is present and to set goals, particularly in cases of bilateral involvement.

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