Estimation of Endurance During Elbow Flexion with Myoelectric Orthotic Assistance

OBJECTIVES: The current study evaluated the powered myoelectric elbow orthosis' (PMEO) impact on fatigue resistance and maximum endurance time (MET) of the gracilis muscle used in FFMT for elbow reconstruction. The PMEO was developed to support elbow flexion by mechanically locking the joint in place, reducing muscular demand during sustained tasks. DESIGN: Experimental clinical study SETTING: Academic medical center PARTICIPANTS: Seven participants with BPI and FFMT were enrolled and divided into more and less impaired groups based on manual muscle test scores. INTERVENTIONS: Participants performed repeated isometric elbow flexion trials with and without the PMEO while surface electromyography (EMG) and kinematic data were recorded. MAIN OUTCOME MEASURES: Spectro-temporal EMG metrics-median power frequency (MPF) and integrated EMG (iEMG)-were analyzed, and endurance was estimated using a muscle-specific MET model. RESULTS: Four of the seven participants, primarily in the more impaired group, demonstrated a 4-minute improvement in MET and more favorable fatigue metrics with the PMEO. MPF increased and iEMG decreased in these individuals, indicating delayed fatigue onset. The PMEO also enabled task completion in three participants who were otherwise unable to flex their elbow unaided. CONCLUSIONS: These results suggest that the PMEO can enhance functional endurance in individuals with BPI and FFMT. Notably, this study provided one of the first applications of spectro-temporal metrics and MET to evaluate fatigue resistance in a FFMT, filling a gap in existing literature.