Neuromuscular electrical stimulation (NMES) remains as one of the effective rehabilitation modalities for addressing recovery of neuromuscular function after a spinal cord injury (SCI). To achieve optimal effects, the NMES interventions that involve or promote voluntary efforts from SCI participants are preferred. However, these interventions are limited by the fact that the active monitoring of voluntary effort, particularly at the stimulated muscle level is unattainable. The objective of the proposed study is to develop SMARTq (Stimulated Muscle Assessment in Real-Time). This novel system will provide a quasi real-time assessment of intrinsic neuromuscular responses of a stimulated muscle during NMES. Specifically, the proposed system will consist of our novel algorithms interfaced with the EMG data acquisition hardware to process the EMG data recorded from a stimulated muscle in real-time during NMES. The term 'quasi' is used to account for the processing delay of approximately 1 to 2 seconds that may potentially occur. The proposed system will be developed and validated using the data collected from the able-bodied (AB) as well as individuals with incomplete SCI (iSCI). The applicability of the system will be evaluated on individuals with complete SCI (cSCI). Our central hypothesis is that the real-time tracking of neuromuscular responses during a train of NMES will provide valuable information on inherent neuromuscular changes, volitional participation, and neuromuscular recovery. The significance of the proposed study is that, if successful, it will deliver a highly novel system which can allow researchers and clinicians to - 1) evaluate the direct electrophysiological effects of varied combination of NMES on a stimulated muscle in real-time; 2) quantify, track and manipulate the levels of voluntary efforts or volitional drive 'on-fly' during NMES for extracting optimal benefits; 3) track the neuromuscular recovery of the stimulated muscle, particularly for cSCI populations, when any functional changes have not been observed yet; and 4) directly observe the neuromuscular fatigue derived from the electrophysiological data at the stimulated muscle. These are highly significant opportunities that can allow the clinicians and researchers to transform the current as well as future NMES interventions into highly effective training modalities as each intervention will be operated at an individual's neuromuscular level.

Inclusion Criteria:

SCI generic criteria - 1) Be able to tolerate electrical stimulation; 2) Be able and willing to comply with study requirements, procedures and verbal instructions; 3) Have been diagnosed with a spinal cord injury by a physician.

Individuals with complete SCI. 1) Be chronic (≥ 1-year post injury); 2) AIS classified as A or B motor-complete;

Individuals with incomplete SCI. 1) Be motor incomplete; 2) Be AIS classified as C or D; 3) have a neurological level of injury from C6 - T6; 4) Have LEMS score > 10; 5) Have Modified Ashworth Scale ≤ 3 for spasticity.

Inclusion criteria for the able-bodied group. 1) Be able and willing to tolerate electrical stimulation; 2) Be able and willing to comply with study requirements, procedures and verbal instructions.

Exclusion Criteria:

Exclusion criteria for all participants. 1) Pregnancy at time of study; 2) History of femur or tibia fracture; 3) Diagnosis with any major cardiovascular or pulmonary disease; 4) Diagnosis with obesity; 5) Diagnosis of lower extremity deep vein thrombosis; 6) Presence of skin lesions or breakdown; 7) Use of electronic implants; 8) Any history of major gastrointestinal problems; 9) difficulty following or responding to commands that would limit the study participation; 10) Currently enrolled in another research study or therapy (from a licensed physical therapist) that is likely to affect participation in this research study.

There will be five participants in each of the three study groups: able-bodied (AB), incomplete spinal cord injury (iSCI), and complete spinal cord injury (cSCI). All participants will be between the ages of 18 and 60 years old. Individuals will be recruited through the Kessler Institute for Rehabilitation System, which includes 3 hospitals and 75 outpatient clinics.

as per the funding agency guidelines.