Background: Isokinetic studies of wrist flexion and extension (WFE) have been conducted mostly in the concentric mode. However, the eccentric counterpart is of specific importance in strength profiling while both modes are differently expressed in women and men. Objective: to characterize the isokinetic concentric and eccentric isokinetic strength of the dominant side WFE, in a group of healthy young women and men and explore their respective internal and external relationships. Methods: 20 women and 20 men were tested while standing with forearm in neutral position, using a RoM of 60° and a speed of 120°/s for both contraction modes. Isometric grip strength was measured using a standard apparatus. Results: Men were significantly stronger than women, the flexors significantly stronger than the extensors and the eccentric strength significantly higher than its concentric counterpart. A correlation matrix based on the concentric and eccentric peak moments of the WFE revealed that men had significantly higher correlation coefficients compared to women. Conclusions: While supporting the efficiency of the test position, the significant sex-related difference in the strength correlations pattern may reflect an acquired-adaptive trait but this assumption requires further research.

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.

Background / Objective: In the isokinetic literature, relatively limited attention has been given 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), 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 and eccentrically, using a single speed of 90°/s. Results: Men were significantly stronger than women in both the concentric and eccentric tests as indicated by both the absolute (Nm) or the bodyweight normalized (Nm/kgbw) representations. However, the bodyweight normalized women/men strength ratio (78.6±8.0%) was significantly higher than the absolute’s (64.1±6.6%). For both the concentric and eccentric effort and irrespective of the representation (absolute or normalized) the U was the strongest muscle group followed successively by F, R and E. This rank order was highly significant statistically. The eccentric/concentric strength ratios: E/CF and E/CU were significantly higher in men than in women with no remarkable inter-sex differences for E/CE and for E/CR. A correlational analysis which included all pairs of the basic isokinetic outcome parameters (e.g., the PM of Fcon) and performed with respect to ‘sex’ using Fisher’s r-to-z transformation, revealed that men had significantly higher overall correlation coefficients compared to women. Conclusions: The uniformity of main findings with respect to both the sex of the participants and the various strength ratios strongly support the validity of the findings. Specifically, the original rank ordering of the wrist muscle can potentially serve as an additional and preliminary guideline for return to normal strength pattern in rehabilitation of the wrist.

Performance fatigability is characterized by a decline in the capacity to maintain force or power during sustained or repeated activity. This exploratory study quantified knee-extensor mechanical performance and rectus femoris surface electromyographic (sEMG) changes during repeated maximal isokinetic knee extensions and explored sex-related differences. Twenty-nine healthy adults (20 men, 9 women; 20–31 years) performed 30 maximal concentric knee extensions at 180°·s⁻¹. Mechanical outcomes were analyzed in all 29 participants, whereas rectus femoris sEMG outcomes were analyzed in 23 participants. Peak torque (PT) decreased by 32.75 ± 11.66% (adjusted p = 6.08 × 10⁻¹¹), work per repetition by 33.35 ± 11.97% (adjusted p = 2.12 × 10⁻¹¹), and mean frequency (MNF) by 23.44 ± 8.33% (adjusted p = 6.08 × 10⁻¹¹). RMS increased significantly from Start to End (adjusted p = 0.000639), with a mean FI-RMS of −17.12 ± 23.11%. FI-PT and FI-work were very strongly associated (ρ = 0.938, adjusted p = 3.71 × 10⁻¹³), whereas no association involving rectus femoris MNF or RMS remained statistically significant after Holm–Bonferroni correction. No statistically significant sex-related differences were detected. Repeated maximal knee extensions reduced mechanical performance and rectus femoris MNF while increasing RMS. FI summarizes Start-to-End change across the measured outcomes; its reliability and validity require further investigation.