Estimation of Endurance During Elbow Flexion With Myoelectric Orthotic Assistance.

OBJECTIVES

This study evaluated the impact of a powered myoelectric elbow orthosis (PMEO) on fatigue resistance and maximum endurance time (MET) of the gracilis muscle used in free functioning muscle transfer (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 (N=7) with brachial plexus injury 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 and integrated EMG-were analyzed, and endurance was estimated using a muscle-specific MET model.

RESULTS

Four of the 7 participants, primarily in the more impaired group, demonstrated a 4-minute improvement in MET and more favorable fatigue metrics with the PMEO. Median power frequency increased, and integrated EMG decreased in these individuals, indicating delayed fatigue onset. The PMEO also enabled task completion in 3 participants who were otherwise unable to flex their elbow unaided.

CONCLUSIONS

These results suggest that the PMEO can enhance functional endurance in individuals with brachial plexus injury and FFMT. Notably, this study provided one of the first applications of spectro-temporal metrics and MET to evaluate fatigue resistance in an FFMT, filling a gap in existing literature.