User training for machine learning controlled upper limb prostheses: a serious game approach.
Morten B Kristoffersen, Andreas W Franzke, Raoul M Bongers and 3 others
PMID 33579326WHAT IT FOUND
Neither game-based nor conventional coaching training improved EMG pattern quality or functional prosthesis use in four adults with upper limb absence.
Direct control with their own prosthesis consistently outperformed machine learning control at these training levels.
Key findings
01Training did not produce consistent improvements in EMG pattern separability or consistency for either the game or conventional coaching group.
02Functional outcomes using the machine learning prosthesis did not improve with training, and baseline performance using participants' own direct control prostheses was consistently superior.
03All four participants who completed the study used two degrees of freedom at the post-test, but none had sufficient control to add a third degree of freedom.
STILL TO COME
How it was doneWhat they found
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What it does not show
Only four of eight recruited participants completed the study, with dropouts due to poor socket fit, fatigue, and scheduling issues. The training period was likely too short to detect functional improvements or robust control of multiple degrees of freedom. Participants had years of experience with their own direct control prostheses but were naïve to the machine learning system and study prosthesis, biasing the comparison. No home training was included, which may have been necessary to achieve proficiency. Socket fit issues caused one exclusion, highlighting the sensitivity of EMG control to hardware configuration.
Declared interests
The study used commercial prosthetic components from Otto Bock. The authors declare no competing interests. Funding was from the European Union's Horizon 2020 research and innovation programme.
The easy way to misread this
Do not conclude that machine learning control is inferior to direct control for experienced users. This pilot found direct control was superior, but participants had years of experience with their own devices and only brief training on the machine learning system. Longer training and home use may change this result.