The objective of this study was to investigate the long-term gait speed effects after treatment with the iStrideTM gait device in the home environment for individuals with gait impairments from chronic stroke. A review of the participants’ gait speed changes over the study period demonstrates notable positive results across the measured time frames.
When assessing the therapeutic value of outcome measure improvement, it is important to consider the magnitude of the change. The minimal clinically important difference (MCID) defines the smallest amount an outcome must change to be considered ‘meaningful’ to patients . For survivors of stroke, several gait speed MCID values have been proposed, and a MCID value 0.16m/s  was selected for comparison in our study (a conservative measurement compared to MCID values of 0.1 m/s  and 0.13 m/s  used in other studies). In our sample, 94% of participants exceeded this MCID during one or more post-treatment time frames. As a group, immediately post-treatment (one-week post-treatment time frame), the average improvement in gait speed measured 0.27 m/s, exceeding the MCID by more than 0.1 m/s. This improvement reached a peak one month post-treatment where the group’s gait speed improvement reached 0.28 m/s and the average speed of our participants reached 0.812 m/s, which also surpasses the ‘unlimited community ambulator’ functional ambulation category threshold. Interestingly, the highest percentage of participants (77.8%) demonstrated improvement beyond the MCID threshold at six months post-treatment. Between one week post-treatment and twelve months post-treatment, our group still maintained a statistically significant improvement and beyond 0.2 m/s gait speed gain, which remains above the associated MCID value. These results are supported by the vast majority of participants (88%) that reported a subjective gait speed improvement as noted by questionnaire results at study completion.
While multiple gait treatment techniques and technologies cite the ability to improve the gait speed of stroke survivors, comparison to studies of various overground gait intervention approaches indicates an improvement of this magnitude (which is also retained and fosters an expected improvement in community participation ability) may be quite unique . Specifically, a 2009 analysis of seven studies and nearly 400 participants found an average gait speed improvement of 0.07m/s after overground gait training . Another study by DePaul and colleagues  used a motor-learning-science-based overground walking program, which resulted in an average 0.14m/s gait speed improvement. Finally, a study by Park et al.  compared the effects of gait training overground versus treadmills and found the largest gait speed improvement, from any of the training conditions, to be 0.1m/s. The reported gait speed improvements from the present study of >0.21 m/s, across all time frames, are approximately two to three times greater than those reported by these gait-focused studies and additionally highlight retention, a critical factor not demonstrated in the prior mentioned studies.
To examine our study results in the context of overall health, we compared the retained gait speed changes (twelve months post-treatment) to important health metrics impacted by gait speed in the literature. Since walking involves the entire body (i.e., integrating cardiopulmonary systems with neurological and musculoskeletal systems), the speed of walking can provide a window into an individual’s overall health. Gait speed has been shown in numerous studies to be strongly associated with quality of life , disabilities , and survival  in older adults (however, it is important to note that these studies generally investigate populations older than 65 years and the average age of our participants was approximately 57 years).
The relationship of gait speed to mortality was investigated by Studenski et al.  using a pooled analysis of nine cohort studies comprising 34,485 individuals (65 years and older, similar numbers of men and women). Participants were followed for between six and 21 years. This study confirmed significant increases in survival per 0.1 m/s of gait speed and produced five and ten-year survival tables for each sex. Relating these findings to our data reveals an expected increased average survival of three years, with some participants potentially adding up to seven years of life expectancy based on their improved gait speed.
Purser et al. studied hospital inpatients in a Department of Veterans Affairs (VA) study with 1,388 participants (65 years and older, mean 74.2 years; 98% male) and followed the participants for twelve months . This study showed that for each 0.1 m/s increase in gait speed, participants had improved health status, improved physical function, reduced basic and instrumental disabilities, as well as decreased hospitalization days and the associated costs. Specifically regarding hospitalizations, each 0.1 m/s increase in gait speed corresponded to 2.3 fewer hospitalization days. Applying these figures to our data yields a potential reduction of approximately five days of hospitalization, per participant.
Lastly, a study by Perera et al. investigated disabilities using a pooled analysis of seven cohort studies comprising 27,220 individuals (65 years and older, similar numbers of men and women) . This study demonstrated gait speed to predict three-year incidence of bathing/dressing dependence, mobility difficulty, as well as a composite outcome of disability and mortality. The risk of disability using the composite outcome decreased 30% for each 0.1 m/s increase in gait speed. Applying the 30% reduction in disability risk to our population indicates a potential three-year disability risk reduction of 65%. While future studies could confirm these projected outcomes after treatment with the gait device, the potential impact on critical health aspects appears considerable.
Stroke survivors with limited ability to participate in their communities show a decline in emotional well-being after stroke [43, 44]. Therefore, maximizing community participation post-stroke has gained recognition as an important goal of stroke rehabilitation . In Figure 4, we present changes to functional ambulation categories during the study period, which reveals a decrease in the number of home ambulators and a subsequent increase in the number of limited community, unlimited community, and normal speed ambulators, after treatment with the gait device. Moreover, 11/18 of the participants (61%) improved and maintained a greater functional ambulation category at their twelve-month follow-up session compared to baseline. Among these individuals were six of the seven participants that began the study as home ambulators. Additionally, this group includes all six participants that were two years or less post-stroke and the most chronic participant who was 25+ years post-stroke at baseline. These interesting results highlight the value of treatment in the immediate two-year post-stroke time frame and further emphasize that meaningful improvement is achievable even many years post-stroke.
Additionally, reviewing the participants’ gait speeds over the twelve-month period appears to reveal several unique patterns of gait speed change and retention. Some participants improved their functional ambulation category post-treatment and maintained this improvement through the twelve-month follow-up, such as Participants A and C, for example. Others demonstrated initial improvement post-treatment but returned to their original ambulation category by the twelve-month follow-up (such as Participant H), and yet others continued to improve their gait speed over the twelve-month period, despite no further treatment (such as Participant I). Future studies would be useful to differentiate these trends, as well as the specific characteristics that may have influenced treatment responsiveness and retention.
There are several limitations to our study. As noted in our inclusion criteria, the clinical trial participants did not receive any additional physical therapy treatment from the clinical trial physical therapists or external physical therapists during the treatment period. However, six participants (Participants D, H, J, K, O, and P) did resume some form of additional physical therapy treatment between the one-week follow-up and twelve-month follow-up. The possibility of additional physical therapy influencing retention of the device treatment effects is a consideration, especially for Participants D, H, J, and O who remained above the gait speed MCID during their period of additional physical therapy. Participants K and P did not maintain gait speed improvement beyond the MCID during their periods of their additional physical therapy services. It is important to note that two-thirds of our participants (12 out of 18 participants) did not receive any additional physical therapy treatment throughout the study duration.
Additionally, when possible, consistent physical therapists were used with each of the participants in this study. This consistency, while minimizing interrater reliability issues, does not permit blinding of therapists and may introduce bias into the outcomes assessments. Also, repeated outcomes testing could introduce a practice effect. Finally, the small sample size limits the generalizability of our findings as well as the interpretation of our results.