BIOMECHANICS OF MOVEMENT-RELATED EFFORT: EFFECTS OF TASK

Abstract

Based upon the importance of effort in determining human movement, it is essential to develop a thorough understanding of the biomechanical quantities generated during specified movements. PURPOSE: To examine how movement-related effort changes between unilateral and bilateral movements involving the elbow joint. METHODS: Ten healthy, young (20-40 years of age), right-hand dominant males participated in the study. Subjects performed repeated elbow flexion/extension movements in the horizontal plane during unilateral (dominant and non-dominant arms) and bilateral (in-phase and anti-phase) tasks at a frequency of 2.0 Hz. Subjects produced angular displacements that corresponded to effort levels of 1, 3, 5, 7, and 9 on a modified Borg-CR10 scale. Motion capture measured the angular position of the elbow joint. Mean angular displacement (MAD), peak angular velocity (PAV), peak angular acceleration (PAA), and peak joint torque (PJT) were calculated for each condition. A three-way ANOVA assessed the effects of arm, task and effort on MAD, PAV, PAA and PJT. RESULTS: There was a significant main effect of task on MAD (F2,8 = 40.04, P < 0.0001), PAV (F2,8 = 27.54, P < 0.0001), PAA (F2,8 = 15.22, P < 0.0001), and PJT (F2,8 = 14.04, P < 0.0005). In addition, there was a significant main effect of effort level on MAD (F4,6 = 103.70, P < 0.0001), PAV (F4,6 = 89.32, P < 0.0001), PAA (F4,6 = 56.34, P < 0.0001), and PJT (F4,6 = 60.94, P < 0.0001). There was also a significant main effect of arm on MAD (F1,9 = 6.72, P < 0.05), PAV (F1,9 = 7.41, P < 0.05), and PAA (F1,9 = 8.21, P < 0.05). However, the main effect of arm on PJT was not significant (F1,9 = 1.44, P = 0.26). CONCLUSION: This study demonstrated the influence of task on movement-related effort through quantification of biomechanical measures. During unilateral tasks, there is an increased sense of effort when using the non-dominant arm due to strength and motor coordination differences. During bilateral tasks, there is a decreased sense of effort when performing in-phase movements due to increased pattern stability.