Innovative stimulated muscle contraction signals based digital muscle marker: a reliable tool for assessing muscle in persons with stroke.

The algorithm behind the digital marker was trained on healthy adults and older adults, not stroke survivors. Although a domain adaptation analysis improved correlations, the model's performance in the stroke population may differ from its performance in the training population. Muscle mass was measured using bioelectrical impedance analysis (BIA), which is less accurate than the gold standards of MRI or CT. A sensitivity analysis using conversion equations to DXA-equivalent values supported the findings, but direct comparison to gold-standard imaging was not performed. The study included only 40 participants from a single rehabilitation hospital, limiting generalizability. The device showed no significant correlation with hand grip strength on the affected side, indicating it may not be useful for assessing upper-limb muscle status in hemiplegic patients.

The study was funded by the Ministry of Trade, Industry and Energy. The device manufacturer, EXOSYSTEMS, recruited part of the healthy control group used for model training.

Do not interpret the high reliability and correlation with leg measures as evidence that this device can accurately assess upper-limb strength or function on the affected side. The study explicitly found no significant correlation between the digital marker and hand grip strength in the paretic hand, likely due to severe motor deficits and zero grip strength in many participants.