Bilateral upper limb surface electromyography analysis during single-operator colonoscopy: Implications for ergonomics and occupational health

BACKGROUND Single-operator colonoscopy is widely used in clinical practice; however, research on bilateral upper limb surface electromyography (sEMG) activity during insertion remains limited. Analyzing sEMG characteristics during colonoscopy can optimize techniques, prevent occupational injuries, and inform the design of ergonomic devices. AIM To analyze bilateral upper limb muscle activation and fatigue during single-operator colonoscopy insertion under different bowel loop configurations. We also propose strategies for ergonomic improvements and occupational health management. METHODS The sEMG signals were recorded from 14 bilateral upper limb muscles of an experienced endoscopist performing a colonoscopy on a simulated colorectal model. Six loop configurations (no loop, “α” loop, reverse “α” loop, “N” loop, “γ” loop, complex loop) were tested. Muscle activation intensity (root mean square) and fatigue [median power frequency (MPF)] were analyzed using myoMUSCLE at a sampling rate of 1500 Hz. Statistical correlations between loop complexity, procedure time, and muscle load were evaluated. RESULTS The insertion time of various intestinal loops is between 53.6 seconds and 112.0 seconds. Significant differences in bilateral upper limb sEMG activity were observed across various intestinal loop states (no loop vs other loops, P < 0.05). Complex loop induced the highest muscle load (left extensor digitorum root mean square at 370.6 μV) and rapid fatigue (right extensor digitorum MPF difference: 31.8%). A marked bilateral asymmetry was observed: The left extensor digitorum maintained consistently high activation across all tasks, while the right forearm muscles exhibited load-specificity to fine control maneuvers. A positive correlation was found between insertion time and MPF slope decline, strongest for the left flexor carpi radialis (r = 0.59) and right middle deltoid (r = 0.57), indicating time-sensitive fatigue in these stabilizer muscles. The data objectively quantify the elevated biomechanical demand imposed by challenging endoscopic maneuvers. CONCLUSION This exploratory biomechanical investigation suggests that complex loops significantly increase muscle strain and fatigue risk. Ergonomic solutions and time-restricted protocols are proposed to mitigate occupational injuries. This study provides biomechanical evidence for optimizing colonoscopy workflows and device design.