Up to 25 individuals living with chronic incomplete spinal cord injury (iSCI) who can stand but have limited ability to elicit a step without physical assistance or upper limb (U/L) support will be recruited for this study. The first objective of the study will aim to investigate the orthotic effect (i.e., immediate effect) of FES on the reactive stepping response. The second objective is to investigate the therapeutic effect of a novel balance intervention, perturbation-based balance training (PBT) combined with FES (i.e., PBT+FES) on reactive stepping ability, measures of postural sway during quiet standing (i.e., biomechanical measures), and scores on clinical measures of balance and walking.

Inclusion Criteria:

1. have a motor incomplete SCI (i.e., AIS grade C or D) that is non-progressive;
2. be at least one year post-injury (i.e., chronic injury);
3. ≥ 18 years old;
4. be able to stand independently for 60 sec;
5. unable to take a step bilaterally without physical assistance or upper extremity support;
6. able to understand spoken English;
7. free of any other condition besides SCI that significantly affects walking or balance (e.g., no vestibular disorder, significant vision loss, stroke);
8. be able to provide informed, written consent.

Exclusion Criteria:

1. Contraindications for EMS. Electrical stimulation will not be used if:

   • it will be applied to areas where it could cause malfunction of electronic devices, including cardiac pacemakers;
   • a woman is pregnant;
   • the applied region has known or suspected malignancy;
   • the person has active deep vein thrombosis or thrombophlebitis;
   • there are active bleeding tissues, or the person has untreated hemorrhagic disorders;
   • there are infected tissues, tuberculosis, or wounds with underlying osteomyelitis;
   • tissues have been radiated in the past six months;
   • there are damaged skin areas or at-risk skin areas that would result in uneven conduction of current;

2. severe spasticity is present in the legs;

3. the person has contractures in the lower limbs that prevent achieving a neutral hip and ankle position, or extended knee;

4. there is a history of prior lower limbs fragility fracture;

5. the leg muscles are unresponsive to electrical stimulation (i.e., peripheral nerve damage in the legs).

6. Pressure sores on pelvis or trunk, where safety harness will be donned.