Assessment of the underlying systems involved in standing balance: the additional value of electromyography in system identification and parameter estimation.
J H Pasma, J van Kordelaar, D de Kam and 3 others
PMID 28915821WHAT IT FOUND
Adding lower-leg EMG and muscle timing and acceleration terms to a balance test made estimates of sensory weighting, reflexes and delays more accurate and dependable.
Patients and treatment decisions were not tested.
Key findings
01In the healthy participants, adding acceleration feedback to a model that already included muscle activation and activation dynamics made the basic parameter estimates as dependable as the simpler model.
02Adding activation dynamics alone made the basic parameter estimates less dependable than the simpler model.
03In simulated data, adding acceleration feedback to a model that already included muscle activation and activation dynamics reduced mean relative differences to 13.1 to 15.1% for basic parameters and 0.7 to 0.8% for activation dynamics.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study included only 20 healthy young adults, so it does not show whether the method works in older adults or in people with stroke, Parkinson disease or vestibular disorders. The outcomes were model accuracy and reliability, not patient balance, falls or treatment response, so the paper does not demonstrate a clinical benefit. The validation used simulated data generated from one experimental condition, which may not represent the noise and variability of real patients. Some parameter estimates were unrealistic or uncertain unless the full EMG and acceleration feedback model was used, such as very low time delays and low intrinsic properties. The paper does not report a primary outcome or a fixed clinical decision rule, so the best measurement combination depends on the chosen model and sensitivity functions.
Declared interests
Stichting voor de Technische Wetenschappen and the Seventh Framework Programme funded the work. The supplied text does not state author conflicts of interest.
The easy way to misread this
Do not conclude that EMG-based balance testing will improve diagnosis or treatment for patients. The best results required muscle activation, activation dynamics and acceleration feedback together, and the study did not test clinical populations.