# Effects of a Short-Term Interactive Biofeedback Therapy Using the Lumbar-Type Hybrid Assistive Limb in Older Adults With Reduced Physical Function

## TL;DR

A short-term therapy using a wearable cyborg device improved physical function in older adults with reduced mobility.

## Contribution

Demonstrates that brief interactive biofeedback therapy with a lumbar-type HAL device can improve physical function in older adults.

## Key findings

- TUG time decreased significantly after a 40-minute HAL-based therapy program.
- Improvements in gait speed and sit-to-stand performance were maintained for up to one month.
- Acute and sustained functional gains were observed in older adults with reduced physical function.

## Abstract

Aim: Efficient rehabilitation strategies for older adults with reduced physical function have not been firmly established. The lumbar-type Hybrid Assistive Limb (HAL) is a wearable cyborg device designed to support trunk function and sit-to-stand movements, and can be conceptualized as an interactive biofeedback therapy platform that may also enhance gait performance. However, few studies have examined the effects of very short-duration exercise protocols using this device in this population. Therefore, we investigated the effects of a brief lumbar-type HAL-based therapy program in older adults with impaired physical function.

Methods: This was a single-arm interventional study. Participants were community-dwelling older adults aged ≥65 years attending day-care rehabilitation at Chigusa Sawayaka Clinic (Nagoya, Aichi, Japan). The therapy program consisted of supervised sessions using the lumbar-type HAL for 10 minutes per session, once per week for four consecutive weeks (total HAL-based therapy time: 40 minutes). The primary outcome was Timed Up and Go (TUG) time. Secondary outcomes were 10-m gait speed, stride length, five-repetition sit-to-stand (SS5) time, and finger-floor distance. All outcomes were assessed at 11 predefined time points: one week before session 1; immediately before and after each of the four sessions; and one week and one month after session 4. These repeated measurements were used to evaluate the effects of the short-duration HAL-based therapy program.

Results: Ten participants (mean age 82.3 ± 10.4 years, range 65-96; five men and five women) completed the program. From the first to the final assessment, TUG time decreased from 18.47 ± 4.33 s to 14.45 ± 4.10 s, and SS5 time decreased from 20.00 ± 4.18 s to 12.58 ± 2.51 s, while gait speed increased from 0.80 ± 0.26 m/s to 0.95 ± 0.35 m/s. In analyses using a linear mixed-effects model, TUG time showed a significant acute improvement from immediately before to immediately after session 1 (Δ -1.91 s, 95% CI -3.57- -0.24), and the mean within-session change across all four sessions was also significant (Δ -1.10 s, 95% CI -1.93- -0.27). These improvements were maintained at one week (Δ -3.49 s, 95% CI -5.15- -1.83) and one month (Δ -3.92 s, 95% CI -5.58- -2.26) after session 4. Gait speed and SS5 times likewise showed significant reductions both after session 1 and in the average within-session effect across the four sessions, and these improvements were preserved at one week and one month after the final session.

Conclusions: Short-duration interactive biofeedback therapy delivered with a lumbar-type HAL was associated with improvements in multiple aspects of physical function in older adults with reduced physical capacity. Future research should evaluate the effects of HAL in randomized controlled trials with a larger sample size and longer follow-up.