Placebo tablet, twice daily, for 10 weeks.

The WISCI II is a walking scale specifically developed for use in clinical trials in persons with incomplete SCI. Walking ability is scored on a 21-point ordinal scale (0-20, where 0 indicates a person is unable to stand and/or participate in assisted walking and 20 indicates a person can walk more than 10m without walking aids or physical assistance), where a lower number indicates higher impairment.

The SCI-FAI is an observational gait assessment instrument that addresses three key domains of walking function in individuals with SCI. The three SCI-FAI subscales are Gait, Assistive Device, and Walking Mobility. Parameters of the SCI-FAI are measured during the first 2 minutes of the 6MWT (see above).

Neurological examination will be performed using the International Standards for Neurological Classification. Sensory scores and lower extremity motor scores are derived at the time of this exam.

The LEMS measures strength in five muscle groups bilaterally (hip flexors, knee flexors and extensors, and ankle dorsiflexors) with the modified British Medical Research Council scale and is performed during the International Standards examination.

The BBS is a 14-item instrument originally designed to assess the risk for falls in community.

Spasticity assessments will be performed at each study visit using the modified Ashworth scale (MAS). Ashworth scores will be averaged across three muscle groups bilaterally: hip adductors, knee extensors, and knee flexors. The Ashworth Scale data will be collected on a 1-5 scale rather than the published 0-4 scale.

The bowel management questionnaire uses a 6-point scale and requires the subject to rate the frequency (0, "Not at all"; 5, "Almost always") of ten items regarding bowel management over the past month.

The bladder management questionnaire uses a 6-point scale and requires the subject to rate the frequency (0, "Not at all"; 5, "Always or almost always") of eight items regarding bladder management over the past month.

The FSFI is a multidimensional, self-report instrument used to assess female sexual function. Six domains are identified that include desire, subjective arousal, lubrication, orgasm, sexual satisfaction, and pain.

The IIEF is a 15-item questionnaire to assess male sexual function. Quality of male sexual function is assessed in 5 domains, with 6 items that assess erectile function, 2 items that address orgasmic function, 2 questions that assess sexual desire, 3 items that assess intercourse satisfaction, and 2 items that assess overall sexual satisfaction.

Pulmonary function testing will be performed (V max Spectra 29N, Carefusion, Yorba Linda, CA) to measure spirometric parameters, static lung volumes, cough strength, and maximal mouth expiratory and inspiratory pressures.

To assess changes in autonomic cardiovascular function, heart rate (3 lead ECG Ivy Biomedical Systems, Inc. Branford, CT) and blood pressure (Finometer Midi, Finapres Medical Systems, Amsterdam, Netherlands) will be continuously monitored at 5 minute intervals at rest and during locomotor training.

The ISCIPDS:B contains core questions about clinically relevant information concerning SCI-related pain that can be collected by health-care professionals with expertise in SCI in various clinical settings. Each person is asked to describe the three worst pain problems he/she is currently experiencing.

The SCIM is a measure of functional ability developed specifically for individuals with SCI to evaluate their performance of activities of daily living (ADL). The SCIM III is composed of 19 items in 3 sub-scales: (a) self-care (6 items, sub-score 0-20); (b) respiration and sphincter management (4 items, sub-score 0-40); and (c) mobility (9 items, sub-score 0-40). The total score ranges from 0 to 100.

The Spinal Cord Injury Functional Index (SCI-FI) is a comprehensive, SCI-specific measure to assess functional activities related to quality of life for individuals with SCI. The SCI-FI covers five distinct functional domains: Ambulation, Basic Mobility, Fine Motor Function, Self-Care (including bowel and bladder), and Wheeled Mobility.

The SF-12 is a generic health-status measure developed by RAND to assess outcomes of medical care and has been used previously by the SCI Model Systems.

The SWLS is a 5-item measure of the single concept of global life satisfaction. The SWLS is currently used in the SCI Model Systems dataset and normative data for individuals with SCI is available.

The CHART is a 32-item self-report measure of major domains of participation, which has also been utilized extensively by SCI Model System researchers. It assesses functioning in 6 domains of normative role functioning: Physical Independence, Mobility, Occupation, Social Integration, Cognitive Independence, & Economic Self-Sufficiency.

The SGI of change is a subject-rated instrument that measures change in the subject's overall status on a 7-point scale. Scores range from 1 (very much improved) to 7 (very much worse).

The study physician will rate on a 7-point scale the subject's overall clinical condition following treatment as compared to that at baseline. Scores range from 1 (very much improved) to 7 (very much worse).

Adverse experience(s) will be recorded on the Adverse Event Case Report Form, including the date and time of onset, severity, the relationship to study intervention, the date of resolution, the action taken, and the outcome of the adverse experience. The responsible physician will make a causality assessment for every adverse experience.

Participants will be provided a list of side-effects associated with dalfampridine treatment. Three lines marked "other" for open-choice responses will accompany the selection of options for forced-choice side-effects. Participants will rate the severity (visual analog scale [VAS]; 0-100) and frequency ("never", "occasionally", "sometimes", "often" or "always") of side effects for each of the forced and open choice answers. Severity and frequency of side-effects will be rated by participants every 2 weeks during the intervention part of the study.