Effects of Using a Lumbar-Type Hybrid Assistive Limb by Older Adults With Frailty on Exercise Self-Efficacy: Retrospective Analysis Based on the Kanagawa Prospective ME-BYO Cohort Study.
Makoto Nagasawa, Sho Nakamura, Yoshinobu Saito and 4 others
PMID 42636433WHAT IT FOUND
A wearable hip-assist robot improved exercise confidence by 1.05 points (on a 4-item, 1-to-5 scale) among 96 frail older adults, with the largest gains in those who had never exercised regularly.
The randomised comparison did not show a clear difference between groups.
Key findings
01Among 96 frail older adults who completed lumbar-type HAL training, exercise self-efficacy increased by 1.05 points (95% CI 0.41–1.69; P = .002) from a baseline mean of 11.94 to 12.99 points.
02In the randomised comparison, the HAL group (n=38) showed a mean ESE change of +1.16 points versus −0.05 points in the waitlist control group (n=38); the between-group difference of 1.21 points did not reach significance (P = .12).
03Participants without an established exercise habit (stages 1–4, n=56) improved by 1.73 points, while those in the maintenance stage (n=38) changed by only 0.05 points; the between-stratum difference was +1.68 points (P = .01).
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The two source studies differed in structure: the feasibility study used individualised training over 20 sessions, while the RCT combined individual and group training over 10 sessions, making it unclear which format drove the effect. The randomised between-group comparison was underpowered: 76 participants were enrolled versus the 172 needed for 80% power, giving post hoc power of only 30–34%, so the non-significant result cannot rule out a meaningful effect. Subgroup analyses by TTM stage had very small cells (stage 1: n=6 pooled; n=2 in the HAL arm and n=4 in the control arm of the RCT), so stage-specific findings are exploratory and hypothesis-generating only. Open recruitment may have preferentially attracted participants with greater health awareness, limiting generalisability to the broader frail population. The primary analysis is a within-person pretest-posttest comparison, not a between-group comparison, so it cannot exclude placebo, regression-to-the-mean, or maturation effects.
Declared interests
This pooled analysis received no specific funding. The source studies were supported by the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT). One author (MN) has been an employee of CYBERDYNE Inc — the manufacturer of the HAL device — since October 2022, though the authors state the company had no role in this study. The authors declare no other conflicts of interest.
The easy way to misread this
Do not read the 1.05-point ESE improvement as proof that the HAL device causes the gain. The primary analysis is a within-person before-and-after comparison with no concurrent control, and the randomised between-group comparison (the design that could support causality) did not reach significance (P =.12) and was powered for only 30–34% of the required sample. The subgroup finding in precontemplators (n=6, +3.50 points) is especially fragile: it rests on six people, was not pre-registered in the original trial protocols, and the authors themselves label it exploratory and hypothesis-generating.