Are the 10 meter and 6 minute walk tests redundant in patients with spinal cord injury?

OBJECTIVE: To evaluate the relationship and redundancy between gait speeds measured by the 10 Meter Walk Test (10MWT) and 6 Minute Walk Test (6MWT) after motor incomplete spinal cord injury (iSCI). To identify gait speed thresholds supporting functional ambulation as measured with the Spinal Cord Injury Functional Ambulation Inventory (SCI-FAI). DESIGN: Prospective observational cohort. SETTING: Seven outpatient rehabilitation centers from the Christopher and Dana Reeve Foundation NeuroRecovery Network (NRN). PARTICIPANTS: 249 NRN patients with American Spinal Injury Association Impairment Scale (AIS) level C (n = 20), D (n = 179) and (n = 50) iSCI not AIS evaluated, from February 2008 through April 2011. INTERVENTIONS: Locomotor training using body weight support and walking on a treadmill, overground and home/community practice. MAIN OUTCOME MEASURE(S): 10MWT and 6MWT collected at enrollment, approximately every 20 sessions, and upon discharge. RESULTS: The 10MWT and 6MWT speeds were highly correlated and the 10MWT speeds were generally faster. However, the predicted 6MWT gait speed from the 10MWT, revealed increasing error with increased gait speed. Regression lines remained significantly different from lines of agreement, when the group was divided into fast (≥0.44 m/s) and slow walkers (<0.44 m/s). Significant differences between 6MWT and 10MWT gait speeds were observed across SCI-FAI walking mobility categories (Wilcoxon sign rank test p<.001), and mean speed thresholds for limited community ambulation differed for each measure. The smallest real difference for the 6MWT and 10MWT, as well as the minimally clinically important difference (MCID) values, were also distinct for the two tests. CONCLUSIONS: While the speeds were correlated between the 6MWT and 10MWT, redundancy in the tests using predictive modeling was not observed. Different speed thresholds and separate MCIDs were defined for community ambulation for each test.

Treatment and enablement in rehabilitation research.

This commentary discusses the distinction between treatment theory and enablement theory as it pertains to rehabilitation research and treatment. The theories are also applied to an example of presented research. I conclude that collaboration between researchers focused on the treatment theory and those focused on enablement theory should be closer than the handoff suggested by Whyte in this supplement.

Assessment of functional improvement without compensation reduces variability of outcome measures after human spinal cord injury.

OBJECTIVE: To develop a scale (Neuromuscular Recovery Scale [NRS]) for classification of functional motor recovery after spinal cord injury (SCI) based on preinjury movement patterns that would reduce variability of the populations' level of function within each class, because assessment of functional improvement after SCI is problematic as a result of high variability of the populations' level of function and the insensitivity to change within the available outcome measures. DESIGN: Prospective observational cohort with longitudinal follow-up. SETTING: Seven outpatient rehabilitation centers from the Christopher and Dana Reeve Foundation NeuroRecovery Network (NRN). PARTICIPANTS: Individuals (N=95) with American Spinal Injury Association Impairment Scale (AIS) grade C or AIS grade D having received at least 20 locomotor training treatment sessions in the NRN. INTERVENTIONS: Intensive locomotor training including stepping on a treadmill with partial body weight support and manual facilitation and translation of skills into home and community activities. MAIN OUTCOME MEASURES: Berg Balance Scale, six-minute walk test, and ten-meter walk test. RESULTS: Individuals classified within each of the 4 phases of the NRS were functionally discrete, as shown by significant differences in the mean values of balance, gait speed, and walking endurance, and the variability of these measurements was significantly reduced by NRS classification. The magnitude of improvements in these outcomes was also significantly different among phase groups. CONCLUSIONS: Assessment with the NRS provides a classification for functional motor recovery without compensation, which reduces variability in performance and improvements for individuals with injuries classified as AIS grades C and D.

Ambulation and balance outcomes measure different aspects of recovery in individuals with chronic, incomplete spinal cord injury.

OBJECTIVE: To evaluate relationships among ambulation and balance outcome measures over time for incomplete spinal cord injury (SCI) after locomotor training, in order to facilitate the selection of effective and sensitive rehabilitation outcomes. DESIGN: Prospective observational cohort. SETTING: Outpatient rehabilitation centers (N=7) from the Christopher and Dana Reeve Foundation NeuroRecovery Network. PARTICIPANTS: Patients with incomplete SCI (N=182) American Spinal Injury Association Impairment Scale level C (n=61) and D (n=121). INTERVENTIONS: Intensive locomotor training, including step training using body weight support and manual facilitation on a treadmill followed by overground assessment and community integration. MAIN OUTCOME MEASURES: Six-minute and 10-meter walk tests, Berg Balance Scale, Modified Functional Reach, and Neuromuscular Recovery Scale collected at enrollment, approximately every 20 sessions, and on discharge. RESULTS: Walking and standing balance measures for all participants were strongly correlated (r≥.83 for all pairwise outcome correlations), standing and sitting balance measures were not highly correlated (r≤.48 for all pairwise outcome correlations), and walking measures were weakly related to sitting balance. The strength of relationships among outcome measures varied with functional status. Correlations among evaluation-to-evaluation changes were markedly reduced from performance correlations. Walk tests, when conducted with different assistive devices, were strongly correlated but had substantial variability in performance. CONCLUSIONS: These results cumulatively suggest that changes in walking and balance measures reflect different aspects of recovery and are highly influenced by functional status and the utilization of assistive devices. These factors should be carefully considered when assessing clinical progress and designing clinical trials for rehabilitation.

NeuroRecovery Network provides standardization of locomotor training for persons with incomplete spinal cord injury.

OBJECTIVE: To illustrate the continuity of care afforded by a standardized locomotor training program across a multisite network setting within the Christopher and Dana Reeve Foundation NeuroRecovery Network (NRN). DESIGN: Single patient case study. SETTING: Two geographically different hospital-based outpatient facilities. PARTICIPANTS: This case highlights a 25-year-old man diagnosed with C4 motor incomplete spinal cord injury with American Spinal Injury Association Impairment Scale grade D. INTERVENTION: Standardized locomotor training program 5 sessions per week for 1.5 hours per session, for a total of 100 treatment sessions, with 40 sessions at 1 center and 60 at another. MAIN OUTCOME MEASURES: Ten-meter walk test and 6-minute walk test were assessed at admission and discharge across both facilities. For each of the 100 treatment sessions percent body weight support, average, and maximum treadmill speed were evaluated. RESULTS: Locomotor endurance, as measured by the 6-minute walk test, and overground gait speed showed consistent improvement from admission to discharge. Throughout training, the patient decreased the need for body weight support and was able to tolerate faster treadmill speeds. CONCLUSIONS: Data indicate that the patient continued to improve on both treatment parameters and walking function. Standardization across the NRN centers provided a mechanism for delivering consistent and reproducible locomotor training programs across 2 facilities without disrupting training or recovery progression.

Variable-frequency-train stimulation of skeletal muscle after spinal cord injury.

Skeletal muscle, after spinal cord injury (SCI), becomes highly susceptible to fatigue. Variable-frequency trains (VFTs) enhance force in fatigued human skeletal muscle of able-bodied (AB) individuals. VFTs do this by taking advantage of the "catch-like" property of skeletal muscle. However, mechanisms responsible for fatigue in AB and SCI subjects may not be the same, and the efficacy of VFT stimulation after SCI is unknown. Accordingly, we tested the hypothesis that VFT stimulation would augment torque-time integral in SCI subjects. The quadriceps femoris muscle was stimulated with constant frequency trains (CFTs) (six 200 s square wave pulses separated by 70 ms) or VFTs (a train identical to the CFT, except that the first two pulses were separated by 5 ms) in SCI and AB subjects. After 180 contractions (50% duty cycle), isometric peak torque decreased 44, 56, and 67 percent, in the AB (n = 10), acute SCI (n = 10), and chronic SCI (n = 12) groups, respectively. In fatigued muscle, VFTs enhanced the torque-time integral by 18 percent in AB subjects and 6 percent in chronic SCI patients, and had no effect in acute SCI patients when compared to the corresponding CFT. The much faster rise times in SCI subjects (approximately 80 ms vs. 120 ms in AB subjects) probably contributed to the inability of VFTs to enhance torque-time integrals in SCI patients. The results suggest that the use of VFT stimulation in patients with SCI may not be as efficacious as it is in AB persons.