ObjectiveTo 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).DesignProspective observational cohort.SettingSeven outpatient rehabilitation centers from the Christopher and Dana Reeve Foundation NeuroRecovery Network (NRN).Participants249 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.InterventionsLocomotor 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.ResultsThe 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.ConclusionsWhile 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.

Study design Clinical trial. Objective To demonstrate that a 12-week exoskeleton-based robotic gait training regimen can lead to a clinically meaningful improvement in independent gait speed, in community-dwelling participants with chronic incomplete spinal cord injury (iSCI). Setting Outpatient rehabilitation or research institute. Methods Multi-site (United States), randomized, controlled trial, comparing exoskeleton gait training (12 weeks, 36 sessions) with standard gait training or no gait training (2:2:1 randomization) in chronic iSCI (>1 year post injury, AIS-C, and D), with residual stepping ability. The primary outcome measure was change in robot-independent gait speed (10-meter walk test, 10MWT) post 12-week intervention. Secondary outcomes included: Timed-Up-and-Go (TUG), 6-min walk test (6MWT), Walking Index for Spinal Cord Injury (WISCI-II) (assistance and devices), and treating therapist NASA-Task Load Index. Results Twenty-five participants completed the assessments and training as assigned (9 Ekso, 10 Active Control, 6 Passive Control). Mean change in gait speed at the primary endpoint was not statistically significant. The proportion of participants with improvement in clinical ambulation category from home to community speed post-intervention was greatest in the Ekso group (>1/2 Ekso, 1/3 Active Control, 0 Passive Control, p < 0.05). Improvements in secondary outcome measures were not significant. Conclusions Twelve weeks of exoskeleton robotic training in chronic SCI participants with independent stepping ability at baseline can improve clinical ambulatory status. Improvements in raw gait speed were not statistically significant at the group level, which may guide future trials for participant inclusion criteria. While generally safe and tolerable, larger gains in ambulation might be associated with higher risk for non-serious adverse events.

-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 (~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. Key words: catch-like property, electrical stimulation, fatigue, spinal cord injury, variable frequency train Abbreviations: AB = able-bodied, A/D = analog/digital, CFT = constant-frequency train, IPI = interpulse interval, m. QF = quadriceps femoris muscle, MVC = maximum voluntary contraction, SCI = spinal cord injury, T20-80 = time from 20 to 80 percent of peak torque, VFT = variable-frequency train.

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Study design: Randomized dual center controlled clinical trial. Objective: To determine and compare the cardiorespiratory impact of 3 months of aquatic and robotic therapy for individuals with chronic motor incomplete spinal cord injury (CMISCI). Settings: Two rehabilitation specialty hospitals. Methods: Thirty-one individuals with CMISCI with neurological level between C2-T12 at least 1 year post injury were randomized to either aquatic or robotic treadmill therapy for 36 sessions. Customized sessions lasted 40-45 min at 65-75% heart rate reserve intensity with peak oxygen consumption (peak VO 2) measured during arm ergometry at baseline and post intervention. Additional peak robotic treadmill VO 2 assessments were obtained before and after training for participants randomized to robotic intervention. Results: Peak VO 2 measured with arm ergometry was not significantly different with either aquatic intervention (8.1%, p = 0.14, n = 15) or robotic intervention (−0.7%, p = 0.31, n = 17). Peak VO 2 measured with robotic treadmill ergometry demonstrated a statistical improvement (14.7%, p = 0.03, n = 17, two-tailed t-test) across the robotic intervention. Comparison between the two interventions demonstrated a trend favoring aquatic therapy for improving arm ergometry peak VO 2 (ANOVA, p = 0.063). Conclusions: Neither 3-month exercise interventions statistically improved arm cycle ergometry peak VO 2 , our cardiorespiratory surrogate marker, although percent improvement was greater in the aquatic exercise condition. Robotic ergometry peak VO 2 did improve for the robotic intervention, confirming previous work. These results suggest that either intervention may hold utility in improving cardiorespiratory fitness in CMISCI, but peak VO 2 measurement technique appears critical in detecting effects. Sponsorship: DOD CDMRP SCI Research Program Clinical Trial Award SC090147, FY 2009. This study is registered under ClinicalTrials.gov Identifier: NCT01407354.