Endurance time
On average, participants performed 9.18±3.13, 8.00±1.90 and 8.88±3.28 trials for elbow, shoulder and trunk fatigue, respectively. Specifically, for shoulder, elbow and trunk fatiguing protocol, females performed 7.80±1.75, 9.00±3.46 and 8.70±3.92 trials, and males performed 8.29±2.21, 9.43±2.82 and 9.14±2.34 trials. There was no difference of endurance time between three fatiguing tasks (shoulder, elbow, and trunk; p<0.0001) and between females and males (p<0.0001) in any of those tasks.
Shoulder angles:
For the shoulder elevation angle, there was a significant interaction effect (p=0.032) between fatigue location and sex. In males, the shoulder elevation angle was the smallest after EF than any other condition (NF: p<0.0001; SF: p=0.001; TF: p=0.027). However, in females, the shoulder elevation angle was the smallest after SF compared to any other condition (NF: p<0.0001; EF: p<0.0001; TF: p<0.0001). As for other shoulder angles, there were no sex*fatigue location interaction or sex main effect. However, there was a significant fatigue location effect on the plane of elevation angle. The plane of elevation angle after SF was the smallest than any other conditions (NF: p=0.011; EF: p<0.0001; TF: p<0.0001). This implied that the humerus was less forward after the SF. Finally, there were no significant effects on shoulder angle variability.
Elbow angles:
No sex*fatigue location interaction or sex main effects were detected on the elbow angles. The elbow flexion/extension angle was the greatest after SF compared to any other conditions (2.61° greater than after NF, p=0.001; 3.30° greater than after EF, p=0.001; and 3.68° greater than after TF, p<0.0001). This indicated that the elbow was more flexed after SF. As for the variability, males had greater elbow flexion/extension variability than females (4.07° greater, p=0.001). In addition, the elbow flexion angle variability was greater after TF compared to NF (1.32° greater, p=0.002) and after SF (1.38° greater, p<0.01).
Spinal angles:
Upper thorax (UL) angles:
There was a significant interaction (p<0.0001) between sex and fatigue location on UL lateral flexion angle. In males, the UL lateral flexion angle was the smallest after SF compared to all other conditions (4.01° smaller than NF, p<0.0001; 3.75° smaller than EF, p<0.0001; 3.21° smaller than TF, p<0.0001). In females however, the UL lateral flexion angle after SF was only smaller than NF (1.29° smaller, p=0.02). This indicated that the upper thorax was leaning towards the non-reaching side the least after SF in males, but for females, the leaning after SF was only less than NF. The interaction effect between sex and fatigue location (p<0.0001) also existed on UL rotation angle. In males, the UL rotation angle was the greatest after SF compared to any other condition (4.17° greater than NF, p<0.0001; 3.58° greater than EF, p<0.0001; 5.06° greater than TF, p<0.0001). In females, the UL rotation angle was not significantly affected by fatigue location. This implied that males rotated the upper thorax right more after SF and females remained the same. There was also an interaction effect between sex and fatigue location (p=0.009) on UL flexion angle. In males, the UL flexion angle was same in all conditions. While in females, the UL flexion angle was the smallest after EF than any other conditions (1.77° smaller than NF, p=0.002; 1.32° smaller than SF, p=0.015; 2.65° smaller than TF, p=0.001). This indicated that females extended the UL less after EF. As for the variabilities, the UL lateral flexion variability was greater after SF than NF (0.15° greater, p=0.04). The UL rotation variability after SF was greater than all conditions (0.26° greater than NF, p=0.013; 0.17° greater than EF, p=0.024; 0.36° greater than TF, p<0.0001). Besides, females had greater UL rotation variability (0.53° greater, p=0.006) and smaller UL flexion variability (0.44° smaller, p=0.038) than males.
Lower thorax (LL) angles:
There was no significant interaction effect between sex and fatigue on LL angles. However, females had significantly greater mean LL lateral flexion angle than males (8.3° greater, p=0.005). Moreover, there was a significant fatigue location effect (p<0.0001) on the LL lateral flexion angle. The LL lateral flexion angle after SF was greater than EF (2.3°, p=0.0002) and TF (2.8°, p<0.0001). It was also greater in NF than in EF (2.5°, p=0.006) and TF (3.0°, p<0.0001). This indicated that after EF and TF, the lower thorax was leaning more towards the non-reaching side compared to NF. The LL rotation angle was greater after TF than SF (1.7°, p=0.007). As for the variabilities, there was an interaction effect between sex and fatigue location on LL lateral flexion variability. In males, there was no significant fatigue location effect. In females however, the LL lateral flexion variability in NF was smaller than it was after SF (0.2° smaller, p=0.0005) and EF (0.2° smaller, p=0.0004). Besides, the LL rotation (0.5° greater in females, p=0.007) and flexion (0.6° greater in females, p=0.014) variabilities were greater in females than they were in males.
Lumbar (LP) angles:
No significant interaction between sex and fatigue location was detected. As for the fatigue location effect, the only significant joint angle change was the LP lateral flexion angle, which was smaller after TF than all other conditions (1.1° smaller than NF, p=0.02; 2.0° smaller than EF, p<0.0001; 2.5° smaller than SF, p<0.0001). This implied that the lumbar was leaning the lumbar towards the non-reaching side the least after the TF. In addition, there was a significant sex difference on the LP lateral flexion angle. Males had greater LP lateral flexion angle than females (5.4° greater, p=0.032). This indicated that males leaned their lumbar region more towards the non-reaching side than the females. As for angular variabilities, there were interaction effects between sex and fatigue location on LP lateral flexion angle variability (p=0.001) and LP rotation angle variability (p<0.0001). In males, the LP lateral flexion variability was greater after SF than after EF (p=0.02) and TF (p=0.02), whereas in females, it was smaller after SF than after EF (p=0.025) and TF (p=0.025). Besides, the LP rotation variability in males was greater after SF than after EF (p=0.003). But in females, it remained the same in all fatigue location conditions.