Cooperative ankle-exoskeleton control can reduce effort to recover balance after unexpected disturbances during walking.
Cristina Bayón, Arvid Q L Keemink, Michelle van Mierlo and 3 others
PMID 35172846WHAT IT FOUND
In ten healthy walkers, an ankle exoskeleton that helped only when a push threatened balance cut muscle effort in the right leg.
It did not improve stability or step recovery, because the participants were already able to keep their balance.
Key findings
01The exoskeleton detected the push and started assisting within about 200 milliseconds.
02Right-leg calf muscle activity dropped when assistance was on, significantly for soleus and gastrocnemius medialis only when the push hit during double support.
03Stability measures and step timing did not change significantly with assistance.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTsWhat it means for SLPs
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What it does not show
Only ten young, able-bodied people took part, so the controller was never tested on the older or neurologically impaired patients who actually need balance help. Only forward pushes were tested; backward and sideways perturbations, which are common in real falls, were not assessed. The detection method assumes a constant walking speed and may miss perturbations if the person keeps changing pace. The exoskeleton's own weight and the fact that participants could tell when it was on mean the no-exoskeleton condition could not be fairly compared for effort. This was a single-session experiment, so it says nothing about whether the benefit holds up over repeated use or a longer training programme.
Declared interests
Funding is listed as the Dutch Research Council (NWO). The text gives no commercial sponsorship or author conflict declarations.
The easy way to misread this
Do not read the reduced calf-muscle activity as proof the exoskeleton improves balance. Stability did not get better; in healthy walkers the body simply worked less hard because it was already safe. The controller's value for patients who cannot recover balance on their own is untested here.