Effects of Exoskeletons on Low-Back Muscular Demands During Unloaded Intermittently Performed Bending Tasks

Repetitive tasks, even when not physically strenuous, can cause overexertion injuries over prolonged durations. While handling heavy loads may be assigned to automated equipment in modern workspaces, bending tasks remain common in a worker's daily routine. Exoskeletons assist to offset loads to less critical body regions, in each task cycle and can provide cumulative benefits. We assessed the effects of Back-Support Exoskeletons (BSEs) in unloaded bending tasks (each task cycle of 60-secs: standing-still (15-sec), bending, sustaining bent posture (30-sec), retracting, standing still (15-sec)) performed intermittently with 15-sec rest (task cycle: relax - 4:1). Twelve participants performed multiple task cycles with/without assistance (of BSE) until they reached a fatigued state. Both subjective (Borg Ratings of Perceived Exertion (RPE) in back and legs) and objective (muscle activation from left (LES) / right (RES) erector spinae muscles) were recorded for each task cycle. Findings revealed that peak amplitude during sustained bending portion in LES was lower with assistance (17%, p-value < 0.001) and in asymmetric vs. symmetric condition (18%, < 0.002), while in RES was lower in symmetric (15%, <0.02). Performing tasks with assistance led to the highest median frequency (82%) in LES vs. no assistance (68%) at medium back and low leg fatigue levels (p-value <0.02) and the trend was similar in RES (78%, 71%, p-value =0.07). Our findings demonstrate the effects of BSEs in intermittently performed trunk flexion tasks that lack handling of heavy loads and may be beneficial for effective implementation of BSEs in industrial workspaces.