Electrical Stimulation for Sitting Balance

FES utilizes short electric pulses through electrodes attached to the skin (Goel et al. 2023). Electrical stimulation pulses go through the skin to stimulate the nerves of muscles beneath the skin, and muscles contract as a result of the electrical stimulation. Specific to balance, FES targets upper motor neurons that help to improve trunk stability (Bergmann et al. 2019). Physiological changes in muscle tone brought about by FES will often remain after FES has stopped (Senthilnathan et al. 2022).

Discussion

Goel et al. (2023) compared the effects of participants either receiving FES on trunk muscles or VR training on static and dynamic sitting balance; it was shown that sitting balance improved in both groups; however, the group who performed VR training showed more significant and clinically relevant results than the group receiving FES (Goel et al. 2023). In addition, the VR group outperformed the FES training group in terms of functional independence (SCIM-III scores; p=.001), though neither group reached clinically significant difference scores (Goel et al. 2023).

Recently, one randomized controlled trial (RCT) assessed the effects of a specific type of electrical stimulation called electromyography triggered electrical stimulation (EMG-ES) (Bayraktar et al. 2024). After four weeks of training, both groups showed improvements in sitting balance outcomes; however, the group who received EMG-ES showed significant improvements compared to the control groups on modified functional reach test (mFRT) and trunk control test scores (p<0.001; effect sizes 0.92, 0.98) (Bayraktar et al. 2024).

One cross-over RCT compared the effects on dynamic sitting balance of participants receiving FES (on erector spinae and rectus abdominis) plus therapeutic exercise (aimed at improving sitting balance and upper body posture) for 6 weeks, twice a week; and participants performing only the exercise (Bergmann et al. 2019). Most of the dynamic sitting balance parameters improved in both groups with no significant differences between groups (Bergmann et al. 2019).

In a pre-post study on FES and trunk stability/reach, Tefertiller et al. (2022) grouped participants with SCI into motor incomplete or motor complete and in those who received wide pulse/high frequency-FES (WPHF-FES) pulse width of 500 μs or 1000 μs (Tefertiller et al. 2022). Only the motor incomplete group experienced statistically significant and clinically meaningful improvements for mFRT (15.6 cm); regarding the pulse width, the 1000 μs group showed larger mFRT change scores (23.4 cm vs. 10.0 cm).

One small pre-post study (N=5) included five patients with motor complete tetraplegia who underwent a task-specific rehabilitation (TSR) intervention with the application of transcutaneous electrical spinal cord stimulation (TSCS) simultaneously at T11 and L1 spinal levels for 12 weeks, followed by the same intervention (but without TSCS) for another 12 weeks (Tharu et al. 2023). Dynamic and static sitting balance (as measured by mFRT, trunk control test and FIST) were assessed at baseline, after the combined intervention (TSCS + TSR), after the intervention alone (TSR) and at 6 weeks follow-up (Tharu et al. 2023). Compared to baseline, dynamic and static sitting balance (as measured by mFRT, trunk control test, and FIST) were shown after the combined intervention and were maintained throughout the follow-up periods (Tharu et al. 2023).

Conclusions

There is level 1 evidence (from 1 RCT: Goel et al. 2023) that a VR training program along with conventional physical therapy provides significant and more clinically relevant improvements in both static and dynamic sitting balance than a training program involving FES for the trunk muscles along with conventional physical therapy in participants with acute (mean time since injury < 8 months) and complete (AIS B, C, or D) SCI.

There is level 2 evidence (from 1 RCT: Bayraktar et al. 2024) that a 4-week training program using EMG-ES for abdominal muscles provides significant improvements in sitting balance (mFRT and trunk control test) compared with an abdominal isometric strengthening exercise program (without stimulation) in participants with complete (AIS A) SCI who continued with their routine rehabilitation program (active or passive range of motion exercises, stretching, and balance coordination exercises).

There is level 2 evidence (from 1 RCT: Bergmann et al. 2019) that the combination of a therapeutic exercise program and FES on trunk muscles for 6 weeks, compared with therapeutic exercise only, provides an improvement in the dynamic sitting balance in patients with chronic tetraplegia.

There is level 4 evidence (from 1 pre-post study: Tharu et al. 2023) that 12 weeks of TSR and the simultaneous application of TSCS at T11 and L1 spinal levels provide significant improvements in dynamic and static sitting balance, and these improvements were maintained at 6 weeks follow-up.

There is level 4 evidence (from 1 pre-post study: Tefertiller et al. 2022) that upper extremity training sessions (consisting of 60 min of functional task-specific practice in combination with WPHF-FES to the trunk and upper extremities, on 15 min of functional training without WPHF-FES, and on home integration training) improve the trunk stability (mFRT) only in patients with acute motor incomplete tetraplegia (and not in acute motor complete tetraplegia).