The influence of three different test positions and thigh asymmetry on measurements of isometric hip flexion strength in men and women.

Purpose: The aim of this study was to compare muscle strength at 90° hip and knee flexion as measured in three different positions and to investigate whether an internal or external deficit in the range of rotation in the hip joint affects flexor muscle strength.

Methods: We measured the peak muscle torque of rotation in the hip joint, using isometric torquemeter, and hip ROM in healthy participants N = 40, aged 21.6 ± 1.9, in three different measurement positions. We tested for differences between the positions, and for the potential influence of participant's sex and ROM asymmetry.

Results: The measured peak muscle torque was affected not only by sex and the value of hip flexion affect, but also by the position in which it is measured. Subjects with restricted external rotation of the hip joint (CERD) had significantly higher flexor peak muscle torque compared to subjects with restricted internal rotation (CIRD), in all but the supine position. For CERD, the results were: Supine (SuP) 1.02 ± 0.26; Sitting (StP) 1.32 ± 0.58; Standing (SP) 1.53 ± 0.47; and for CIRD, the results were: Supine (SuP) 1.05 ± 0.17; Sitting (StP) 1.05 ± 0.40; Standing (SP) 1.47 ± 0.53.

Conclusions: Overall, measurement position and passive ROM significantly influence the peak muscle torque in isometric conditions. Moreover, an imbalance in thigh rotation movement significantly determines the magnitude of muscle torque of the hip flexion movement. Individuals with increased internal-toexternal rotation achieved significantly higher values for flexor muscle torque force moments. Overall, these findings are of importance for interpreting or comparing any reported values for muscle torque force moments.