Functional Electrical Stimulation (FES) to Improve Walking

Discussion

To date, there are few randomized controlled or blinded assessments of the training effects of FES to improve mobility after SCI. Furthermore, only six of the studies reviewed here (Duffell et al. 2019; Granat et al. 1993; Gurcay et al. 2022; Kuhn et al. 2014; Klose et al. 1997) report specific usage parameters for FES during gait rehabilitation, whereby FES was applied for at least 20 min, 2 to 5 times/week for up to 4.5 months. In the remainder of the studies, participants were provided with FES systems to use at home “as much as possible” or “as desired” over the course of the study (Ladouceur & Barbeau 2000a; 2000b; Wieler et al. 1999; Stein et al. 1993). Results from the nine pre-post studies included here show that almost all the participants showed improvements in gait parameters (walking speed or distance) when FES was used (Gurcay et al. 2022; Kuhn et al. 2014; Ladouceur & Barbeau 2000a; 2000b; Wieler et al. 1999; Klose et al. 1997; Granat et al. 1993; Stein et al. 1993). This is not surprising, given that the FES could compensate for weakened or paralyzed muscle function during gait.

Of greater interest is the finding of carryover effects after FES training. Several investigators have also reported a carryover effect after FES training such that improvements in functional ambulation (e.g., overground walking speed and distance, step length) persisted even when the stimulator was turned off (Ladouceur & Barbeau 2000b; Wieler et al. 1999). This suggests that neuroplastic changes may have taken place in response to regular use of FES during walking. Indeed, it has been shown in people without disabilities that the combination of treadmill walking and FES led to an acute increase in corticospinal excitability that persists even after the cessation of FES (Thompson & Stein 2004). The use of FES and weight-bearing also helps to maintain the subtalar and midfoot joint mobility needed for walking (Bittar &Cliquet 2010).

Despite the positive findings of FES usage in multiple pre-post studies, the one RCT that we found in people with SCI was less conclusive. In comparing a 12-week full body exercise program that included FES cycling versus an upper body exercise program, there were no differences between groups in 6MWT, 10MWT, or improvements in falls concerns (Galea et al. 2018). The authors stated that the heterogeneity of their sample, which included participants with a range of injury levels and severity, may have contributed to these results (Galea et al. 2018).

Although laboratory studies advocate the efficacy of FES systems for improving ambulatory function in patients with SCI, the effectiveness of any technology is only as good as its acceptance by the intended users. Some have reported difficulties with finding the proper stimulation site or technical difficulties with the leads, switches, or electrodes (Wieler et al. 1999). There have also been reports of musculoskeletal complications such as ankle sprain, calcaneum fracture, back pain, or falls with FES use (Brissot et al. 2000; Gallien et al. 1995). Some of these complications may have been associated with the commencement of upright exercise (gait) after a period of being non-ambulatory. Anecdotal reports found in several studies suggest that most participants mainly use FES indoors or at home, for short-distance walking, to prevent complications due to prolonged immobilization, and to enhance physical fitness rather than functional community ambulation (Brissot et al. 2000; Gallien et al. 1995; Klose et al. 1997).

The functional benefits derived from FES are also quite variable. For instance, Stein et al. (1993) reported that most participants showed a modest improvement in gait speed (average: 0.07 m/s), which was more significant for people with more severe disabilities. Higher-functioning participants felt that this small benefit in gait speed did not warrant the daily use of FES. In contrast, Ladouceur and Barbeau (2000b) reported that there was a tendency for the participants with initially faster gait speed to have greater absolute improvements. Thus, outcomes from FES-use also seem to be quite variable in terms of walking speed or distance (Ladouceur & Barbeau 2000b; Stein et al. 1993; Klose et al. 1997).

Conclusions

There is level 1 evidence (from 1 RCT: Galea et al. 2018) that a multimodal exercise training program (comprising BWSTT, FES cycling, and trunk and upper and lower limb exercises) does not provide better neurological or walking improvements than an upper body exercise program in patients with chronic SCI.

There is level 4 evidence (from 8 pre-post studies: Gurcay et al. 2022; Kuhn et al. 2014; Ladouceur and Barbeau 2000a; 2000b; Wieler et al. 1999; Klose et al. 1997; Granat et al. 1993; Stein et al. 1993) that FES-assisted walking or cycling can enhance walking speed and distance in people with complete and incomplete SCI.

There is level 4 evidence from two independent laboratories (Ladouceur & Barbeau 2000a, 2000b; Wieler et al. 1999) that the regular use of FES in gait training or activities of daily living leads to persistent improvement in walking function that is observed even when the stimulator is not in use.