The central nervous system adjusts muscle synergy structure and tightly controls rollator-supported transitions between sitting and standing.
Michael Herzog, Frieder C Krafft, Janis Fiedler and 4 others
PMID 40281643WHAT IT FOUND
Healthy young adults used more upper body and less leg muscle when gripping rollator handles.
The brain did not change its core movement pattern, only the muscle balance. This shifts load from weak legs to arms but requires further testing in older, fall-prone users.
Key findings
01Full support with rollator handles increased upper body muscle weighting and decreased lower limb muscle weighting, particularly around the critical moment of leaving the seat.
02The central nervous system did not create new movement patterns for rollator use; instead, it reused existing temporal muscle synergies but shifted the effort from legs to arms.
03In challenging balance conditions, rollator support specifically reduced the activity of muscles around the ankle, which are crucial for postural stability.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTs
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What it does not show
The study used only young, healthy adults (mean age 25.5 years), so the results may not apply to older adults with age-related muscle weakness or neurological conditions. The rollator simulator was heavier and more rigid than commercial rollators, which might alter how much users could lean or pull. Foot placement was restricted to a standardized position, preventing natural adjustments like pulling feet back, which is common in real-world sit-to-stand. It is unclear if 'light touch' participants applied more force than intended, potentially blurring the line between haptic cueing and physical support.
Declared interests
Funded by JuBot, Carl-Zeiss-Foundation, HEiKA, and KIT. No commercial conflicts of interest regarding the specific rollator device used were declared, but the funding bodies include technology and research partnerships.
The easy way to misread this
Do not assume that rollator use is safer for older adults because it reduces leg muscle demand. This study was in young, healthy adults. The reduction in ankle muscle activity and the reliance on upper body strength could be detrimental or impossible for frail older adults with poor balance or weak arms.