Assessment of hip abductor and adductor muscle strength with fixed-frame dynamometry: Considerations on the use of...

To examine the specificities and limitations of bilateral and unilateral tasks for the assessment of hip abductor and adductor strength with a commercially-available fixed-frame dynamometer.

Correlational/validity study.

Maximal voluntary isometric strength of hip abductors and adductors was evaluated in 130 healthy participants using unilateral and bilateral tasks. Surface EMG activity of agonist and stabilizer muscles was concomitantly recorded in a subgroup of 15 participants.

For both muscle groups, bilateral tasks resulted in higher strength values than unilateral tasks (∼25%; p < 0.001). The correlation between left- and right-side data was higher for bilateral than unilateral tasks (p < 0.05), thereby resulting in lower interlimb asymmetries (p < 0.001). Agonist EMG activity was lower for unilateral than bilateral tasks (p < 0.01). Stabilizer EMG activity (external abdominal oblique) was higher for unilateral than bilateral tasks (p < 0.05) on the ipsilateral and contralateral side for hip abductors and adductors, respectively.

A large (25%) and quasi-systematic bilateral facilitation of strength was observed for both hip abductors and adductors. Bilateral testing led to an underestimation of interlimb asymmetries, due to higher side equivalence than unilateral tasks. Unilateral testing resulted in lower agonist EMG activity and higher stabilizer activity than bilateral tasks, especially in weaker subjects.