Isokinetic Strength Profile of the Wrist Muscles: A Study of Healthy Women and Men

Objective: In the isokinetic literature, relatively limited attention has been paid to muscles of the wrist. Therefore, the objective of this study was to present an isokinetic profile of these muscles comprising the flexors (F); extensors (E); and ulnar (U) and radial (R) deviators. Method: The dominant-side F, E, U and R in 40 healthy participants (20 women and 20 men) were tested concentrically (Con) and eccentrically (Ecc) using a single speed of 90°/s. Results: Men were significantly stronger than women in both the Con and Ecc tests, as indicated by both the absolute (Nm) and the bodyweight-normalized (Nm/kgbw) representations. However, the bodyweight-normalized women/men strength ratio (78.6 ± 8.0%) was significantly higher than the absolute strength ratio (64.1 ± 6.6%). For both the Con and Ecc tests, and irrespective of the representation (absolute or normalized), the U was the strongest muscle group, followed successively by the F, R and E. This rank order was highly significant statistically. The eccentric/concentric strength ratios, E/C_F and E/C_U, were significantly higher in men than in women, with no remarkable inter-sex differences for E/C_E and for E/C_R. A correlational analysis, which included all pairs of basic isokinetic outcome parameters (e.g., the PM of F_con), was performed with respect to 'sex' using a nonparametric bootstrap procedure, revealing that men had significantly higher overall correlation coefficients compared to women. Conclusions: The consistency of the main findings with respect to both the sex of the participants and the various strength ratios supports the use of the current protocol. The observed strength order (U > F > R > E) may assist clinicians in setting preliminary return-to-function targets after wrist rehabilitation.