Because of the range in the number of training sessions that were completed by the participants, we examined whether there was a relationship between the 10MWT or mEFAP scores and the number of training sessions (Fig. 2). The duration of training (number of training sessions) was not significantly related to changes in the gait velocity (r = 0.52, P = 0.29), mEFAP scores (r = 0.32, P = 0.54), and no clear trends could be discerned. There was also no significant relationship between the Chedoke-McMaster foot or leg scores and functional ambulation outcomes, although there is a slight trend for participants with more physical impairment (ie, lower Chedoke-McMaster scores) to have greater percent improvement in functional ambulation (Fig. 2).
This study examined the effect of a treadmill-based locomotor training protocol using leg weights on functional ambulatory capacity. Although the sample size of this pilot study is small, the results indicate that treadmill-based locomotor training with leg weights is feasible and could be an effective strategy to improve functional ambulation in people with chronic stroke. Most participants showed an improvement in functional gait parameters, such as gait velocity and the ability to climb stairs, and an increase in the proportion of the step cycle spent in swing on the paretic side.
Recent evidence suggests that improvements in walking function posttraining could be attributed to changes in cortical drive during locomotion. Studies using transcranial magnetic stimulation or functional magnetic resonance imaging have indicated that there are increases in descending motor excitability and increases in the size of the cortical representation of lower limb muscles after single59 or repeated60–62 bouts of treadmill-based locomotor training in individuals with stroke. Enhanced cortical excitability and representation of the tibialis anterior muscle was also recently shown to be correlated to improved balance and step length following treadmill-based locomotor training.60 Improvements in functional ambulation were also shown to be associated with increased activation of cerebellar and midbrain areas after a six-month treadmill exercise program in individuals with chronic stroke.62 Considering that there is a particular contribution of cortical input to lower limb flexor muscles during walking,63–66 it is quite possible that changes in supraspinal input could have contributed to the changes in functional ambulation that we observed here after treadmill-based locomotor training with leg weights.
One previous study investigated the effect of leg weights in a small group (n = 3) of stroke survivors over a five-day training period.34 No significant effects on gait velocity were noted. In this study, participants underwent more intensive treadmill-based locomotor training with leg weights for a minimum of four weeks, three times per week. In addition, the amount of weight added to the legs was adjusted as a proportion of body weight and was based on previous findings about the relationship between added weight and level of flexor muscle activation during swing.30 However, we found no significant effects on overground gait velocity. Given that most of our participants’ initial gait velocity was in the range associated with the least-limited to full community ambulators,67 it may not be surprising that further improvements in gait velocity were not seen. Indeed, it was the participant who had the lowest initial gait velocity (S6) who showed the most marked improvements. In addition, we also note that four of our participants (S1, S3, S5, and S6) demonstrated a change in gait velocity of >0.10 m/sec. The standard error of measurement of the 10MWT has been reported to be 0.04 m/sec, and a change of 0.10 m/sec has been determined to be the threshold for determining substantial meaningful change in functional mobility.68
This was a pilot study that used a small sample of community-dwelling participants with mild stroke. Functional improvements in gait after treadmill-based locomotor training in these populations have been observed previously,48,49 so we cannot rule out the possibility that the positive effects that we observed could be attributable just to the training and not to a specific effect of the leg weights. Future studies stemming from this research are planned to include a larger sample of participants and the inclusion of a control intervention.
The amount of added weight around the leg was standardized at 5% of body weight. It is possible that this may not have provided enough of a training effect to significantly improve walking speed, stair climbing, or obstacle-crossing ability. Considering that many of our participants already had initial overground gait velocities more than 0.90 m/sec, modest improvements in this variable may not be surprising. Nevertheless, we still observed an overall mean improvement in gait velocity of 19% as well as promising results in the more difficult task of stair climbing, which improved in almost all participants. Further studies should determine whether this protocol may be improved by standardizing the amount of added weight according to the lower limb strength or ambulatory capacity rather than to body weight. This protocol was otherwise found to be safe and feasible with median Borg ratings of somewhat hard across all participants.
This pilot study demonstrates that treadmill-based locomotor training combined with leg weights could be a feasible approach for improving the ability to perform complex walking tasks, such as stair climbing, in individuals with chronic stroke. Further work must be conducted to differentiate the specific benefit of adding leg weights versus the effect of treadmill-based locomotor training alone.
The authors thank A. Burke, B. Cowie, F. Lam, S. Liu, S. Hua, J. Shcherbakova, and T.D. Wingson for their valuable assistance and to all the participants who took part in this study. Tania Lam is a Canadian Institutes of Health Research New Investigator.
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