Hip external and internal rotation strength: Consistency over time and between sides

Little research has focused on the measurement of both hip external and internal rotation strength. The purpose of this study was to describe the consistency of isometric hip rotation forces measured by hand-held dyanamometry. Specifically, we described the consistency over time and between sides. For 15 subjects measured during 2 sessions one week apart, rotation forces and force ratios did not differ significantly. Intraclass correlation coefficients (ICCs) were high (0.836-0.944) except for the external to internal rotation force ratio on the right side (0.367). For 32 subjects measured during 1 session, hip external rotation forces and rotation force ratios did, but hip internal rotation forces did not, differ between sides. The between-side ICCs were high for the force measures (0.897&0.901) but not for the force ratio (0.337). Unlike force ratios, isometric force measurements obtained during a previous test session or from the other side provide a basis for measurement interpretation. The method errors and coefficients of variation of the method error that we report may be helpful in such interpretation.