Quantifying muscle coactivation in individuals with incomplete spinal cord injury using wavelets.

BACKGROUND: Individuals with incomplete spinal cord injury often have decreased gait function and coactivation of antagonistic muscle pairs. Common ways of quantifying coactivation using electromyographic signals do not consider frequency information in the signal. As electromyographic signals from different motor unit types have different frequency components and muscle fiber type can change in individuals with spinal cord injury, it may be beneficial to consider frequency components. The aims were to demonstrate the utility of using a method which considers temporal and frequency components of the electromyographical signal to quantify coactivation in lower extremity muscles in individuals with incomplete spinal cord injury through 1) comparison with able-bodied individuals and 2) comparison before and after body weight supported treadmill training. METHODS: Frequency decomposition techniques were applied to electromyographical signals to consider the temporal and frequency components of the electromyographical signals to quantify coactivation over a range of frequencies. RESULTS: Our main findings show that correlation coefficients between total EMG intensities of rectus femoris-biceps femoris and medial gastrocnemius-tibialis anterior were significantly different between able-bodied individuals and those with incomplete spinal cord injury (p = 0006, p = 0.01). The correlation spectra of medial gastrocnemius-tibialis anterior of the spinal cord injury group were substantially different than those the able-bodied group, while the EMG normalcy score was significantly different (p = 0.002). We also found that there was a change in coactivation of ankle muscles after body weight supported treadmill training. INTERPRETATION: Our findings indicate that there may be frequency specific differences in muscle coactivation between able-bodied individuals and those with incomplete spinal cord injury. Changes in coactivation were also observed before and after body weight supported treadmill training. These differences may reflect the changes in recruitment patterns of different motor unit types.

Utility of Equations to Estimate Peak Oxygen Uptake and Work Rate From a 6-Minute Walk Test in Patients With COPD in a Clinical Setting.

PURPOSE: To determine the utility of equations that use the 6-minute walk test (6MWT) results to estimate peak oxygen uptake ((Equation is included in full-text article.)o2) and peak work rate with chronic obstructive pulmonary disease (COPD) patients in a clinical setting. METHODS: This study included a systematic review to identify published equations estimating peak (Equation is included in full-text article.)o2 and peak work rate in watts in COPD patients and a retrospective chart review of data from a hospital-based pulmonary rehabilitation program. The following variables were abstracted from the records of 42 consecutively enrolled COPD patients: measured peak (Equation is included in full-text article.)o2 and peak work rate achieved during a cycle ergometer cardiopulmonary exercise test, 6MWT distance, age, sex, weight, height, forced expiratory volume in 1 second, forced vital capacity, and lung diffusion capacity. Estimated peak (Equation is included in full-text article.)o2 and peak work rate were estimated from 6MWT distance using published equations. The error associated with using estimated peak (Equation is included in full-text article.)o2 or peak work to prescribe aerobic exercise intensities of 60% and 80% was calculated. RESULTS: Eleven equations from 6 studies were identified. Agreement between estimated and measured values was poor to moderate (intraclass correlation coefficients = 0.11-0.63). The error associated with using estimated peak (Equation is included in full-text article.)o2 or peak work rate to prescribe exercise intensities of 60% and 80% of measured values ranged from mean differences of 12 to 35 and 16 to 47 percentage points, respectively. CONCLUSIONS: There is poor to moderate agreement between measured peak (Equation is included in full-text article.)o2 and peak work rate and estimations from equations that use 6MWT distance, and the use of the estimated values for prescription of aerobic exercise intensity would result in large error. Equations estimating peak (Equation is included in full-text article.)o2 and peak work rate are of low utility for prescribing exercise intensity in pulmonary rehabilitation programs.

Training with robot-applied resistance in people with motor-incomplete spinal cord injury: Pilot study.

UNLABELLED: People with motor-incomplete spinal cord injury (m-iSCI) can recover basic walking function but still have difficulty performing the skilled walking required for everyday environments. We hypothesized that a robotic-based gait rehabilitation strategy founded on principles of motor learning would be a feasible and potentially effective approach for improving skilled walking in people with m-iSCI. Fifteen individuals with chronic (>1 yr) m-iSCI were randomly allocated to body weight-supported treadmill training (BWSTT) with Lokomat-applied resistance (Loko-R) or conventional Lokomat-assisted BWSTT (Control). Training sessions were 45 min, 3 times/week for 3 mo. Tolerance to training was assessed by ratings of perceived exertion and reports of pain/soreness. Overground skilled walking capacity (Spinal Cord Injury-Functional Ambulation Profile [SCI-FAP]), as well as walking speed and distance were measured at baseline, posttraining, and 1 and 6 mo follow-up. Our results indicate that Loko-R training could be feasibly applied for people with m-iSCI, although participants in Loko-R tended to report higher levels of perceived exertion during training. Participants in the Loko-R group performed significantly better in the SCI-FAP than Control at posttraining and in follow-up assessments. This study provides evidence that Loko-R training is feasible in people with m-iSCI. Furthermore, there is preliminary evidence suggesting that Loko-R may help improve performance in skilled overground walking tasks. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov; NCT00610974. "Enhancing Walking in People With Incomplete Spinal Cord Injury: a Pilot Study"; https://clinicaltrials.gov/ct2/show/NCT00610974.

Using robot-applied resistance to augment body-weight-supported treadmill training in an individual with incomplete spinal cord injury.

BACKGROUND AND PURPOSE: The efficacy of task-specific gait training for people with spinal cord injury (SCI) is premised on evidence that the provision of gait-related afferent feedback is key for the recovery of stepping movements. Recent findings have shown that sensory feedback from flexor muscle afferents can facilitate flexor muscle activity during the swing phase of walking. This case report was undertaken to determine the feasibility of using robot-applied forces to resist leg movements during body-weight-supported treadmill training (BWSTT) and to measure its effect on gait and other health-related outcomes. CASE DESCRIPTION: The patient described in this case report was a 43-year-old man with a T11 incomplete chronic SCI. He underwent 36 sessions of BWSTT using a robotic gait orthosis to provide forces that resist hip and knee flexion. OUTCOMES: Tolerance to the training program was monitored using the Borg CR10 scale and heart rate and blood pressure changes during each training session. Outcome measures (ie, 10-Meter Walk Test, Six-Minute Walk Test, modified Emory Functional Ambulation Profile [mEFAP], Activities-specific Balance Confidence Scale, and Canadian Occupational Performance Measure) were completed and kinematic parameters of gait, lower-extremity muscle strength (force-generating capacity), lower-limb girth, and tolerance to orthostatic stress were measured before and after the training program. DISCUSSION: The patient could tolerate the training. Overground walking speed, endurance, and performance on all subtasks of the mEFAP improved and were accompanied by increased lower-limb joint flexion and toe clearance during gait. The patient's ambulatory self-confidence and self-perceived performance in walking also improved. These findings suggest that this new approach to BWSTT is a feasible and potentially effective therapy for improving skilled overground walking performance.