Abstract
BackgroundFemales are reported to have a higher risk of musculoskeletal disorders than males. Among risk factors for musculoskeletal disorders, the mechanism of muscle fatigue remains unclear. Especially how females and males adapt to localized fatigue is poorly understood. The purpose of the study was to examine the sex-specific effects of fatigue location on shoulder, elbow and spinal joint angles, and angular variabilities during a repetitive pointing task.MethodsSeven males and ten females performed a standing repetitive pointing task when they were non-fatigued (NF), elbow-fatigued (EF), shoulder-fatigued (SF) and trunk-fatigued (TF), while trunk and upper body tridimensional kinematic data was recorded. Joint angles and angular variabilities of shoulder, elbow, upper thorax, lower thorax, and lumbar were calculated. ResultsResults showed that shoulder angles changed the most after EF in males, but after SF in females. The similarities between sexes were that SF increased the variabilities at upper (lateral flexion: 0.15° greater than NF, rotation: 0.26° greater than all other conditions) and lower thorax (lateral flexion: 0.13° greater than NF, rotation: averagely 0.1° greater than all other condition) in both sexes. TF altered upper thorax variability (0.36° smaller than SF), lower thorax angle (lateral flexion: 3.00° greater than NF, rotation: 1.68° greater than SF), and lumbar angle (averagely 1.8° smaller than all other conditions) in both sexes. However, females had greater lower thorax angle (lateral flexion: 8.3° greater, p=0.005) as well as greater upper (rotation: 0.53° greater, p=0.006) and lower thorax (rotation: 0.5° greater, p=0.007; flexion: 0.6° greater, p=0.014) angular variabilities.ConclusionsThe overall greater lower and upper thorax angular variabilities suggested a more unstable spinal movement pattern in females. The kinematic differences between sexes highlighted a few sex differences in adapting the localized muscle fatigue.
Muscle fatigue assessment during robot-mediated movements
