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Study design: This research utilized a cross-sectional design. Objectives: Spinal cord edema length has been measured with T2-weighted sagittal MRI to predict motor recovery following spinal cord injury. The purpose of our study was to establish the correlational value of axial spinal cord edema using T2-weighted MRI. We hypothesized a direct relationship between the size of damage on axial MRI and walking ability, motor function and distal muscle changes seen in motor incomplete spinal cord injury (iSCI). Setting: University-based laboratory in Chicago, IL, USA. Methods: Fourteen participants with iSCI took part in the study. Spinal cord axial damage ratios were assessed using axial T2-weighted MRI. Walking ability was investigated using the 6-min walk test and daily stride counts. Maximum plantarflexion torque was quantified using isometric dynomometry. Muscle fat infiltration (MFI) and relative muscle cross-sectional area (rmCSA) were quantified using fat/water separation magnetic resonance imaging. Results: Damage ratios were negatively correlated with distance walked in 6 min, average daily strides and maximum plantarflexion torque, and a negative linear trend was found between damage ratios and lower leg rmCSA. While damage ratios were not significantly correlated with MFI, we found significantly higher MFI in the wheelchair user participant group compared to community walkers. Conclusions: Damage ratios may be useful in prognosis of motor recovery in spinal cord injury. The results warrant a large multi-site research study to investigate the value of high-resolution axial T2-weighted imaging to predict walking recovery following motor incomplete spinal cord injury.

Background and Purpose. Performance of therapist-assisted, body-weight–supported treadmill training (BWSTT) to enhance walking ability of people with neurological injury is an area of intense research. Its application in the clinical setting, however, is limited by the personnel and labor requirements placed on physical therapists. Recent development of motorized (“robotic”) rehabilitative devices that provide assistance during stepping may improve delivery of BWSTT. Case Description. This case report describes the use of a robotic device to enhance motor recovery and ambulation in 3 people following motor incomplete spinal cord injury. Interventions. Changes in motor impairment, functional limitations, and locomotor disability were monitored weekly during robotic-assisted BWSTT and following transition to therapist-assisted BWSTT with the assistance of one therapist. Outcomes. Following this training, 2 patients recovered independent over-ground walking and another improved his gait speed and endurance. Discussion. The use of robotic devices may assist physical therapists by providing task-specific practice of stepping in people following neurological injury.

Study Design: This research utilized a cross-sectional design with control group inclusion. Objectives: Preliminary evidence suggests that a portion of the patient population with chronic whiplash may have sustained spinal cord damage. Our hypothesis is that in some cases of chronic whiplash-associated disorders (WAD), observed muscle weakness in the legs will be associated with local signs of a partial spinal cord injury of the cervical spine. Setting: University based laboratory in Chicago, IL, USA. Methods: Five participants with chronic WAD were compared with five gender/age/height/weight/body mass index (BMI) control participants. For a secondary investigation, the chronic WAD group was compared with five unmatched participants with motor incomplete spinal cord injury (iSCI). Spinal cord motor tract integrity was assessed using magnetization transfer imaging. Muscle fat infiltration (MFI) was quantified using fat/water separation magnetic resonance imaging. Central volitional muscle activation of the plantarflexors was assessed using a burst superimposition technique. Results: We found reduced spinal cord motor tract integrity, increased MFI of the neck and lower extremity muscles and significantly impaired voluntary plantarflexor muscle activation in five participants with chronic WAD. The lower extremity structural changes and volitional weakness in chronic WAD were comparable to participants with iSCI. Conclusion: The results support the position that a subset of the chronic whiplash population may have sustained partial damage to the spinal cord. Sponsorship: NIH R01HD079076-01A1, NIH T32 HD057845 and the Foundation for Physical Therapy Promotion of Doctoral Studies program.

There is sparse literature on the profile of action potential firing rate (spike-frequency) adaptation of vertebrate spinal motoneurons, with most of the work undertaken on cells of the adult cat and young rat. Here, we provide such information on adult turtle motoneurons and spinal ventral-horn interneurons. We compared adaptation in response to intracellular injection of 30-s, constant-current stimuli into high-threshold versus low-threshold motoneurons and spontaneously firing versus non-spontaneously-firing interneurons. The latter were shown to possess some adaptive properties that differed from those of motoneurons, including a delayed initial adaptation and more predominant reversal of adaptation attributable to plateau potentials. Issues were raised concerning the interpretation of changes in the action potentials' afterhyperpolarization shape parameters throughout spike-frequency adaptation. No important differences were demonstrated in the adaptation of the two motoneuron and two interneuron groups. Each of these groups, however, was modeled by its own unique combination of action potential shape parameters for the simulation of its 30-s duration of spike-frequency adaptation. Also, for a small sample of the very highest-threshold versus lowest-threshold motoneurons, the former group had significantly more adaptation than the latter. This finding was like that shown previously for cat motoneurons supplying fast- versus slow twitch motor units.

In mammalian spinal motoneurons (MNs), the slow component of the afterhyperpolarization (AHP) that follows the spike of each action potential is a major but not the sole determinant of the cells' firing rate. In this brief historical review, we emphasize four points about the AHP-firing rate relation. (1) There is a relatively sparse literature across vertebrates that directly addresses this topic. (2) After the advent of intracellular recording in the early 1950s, there was evidence from mammals to the contrary of an idea that subsequently became prevalent: that the high-firing rates attainable by spinal interneurons (INs) and low-threshold MNs was attributable to their small AHP at rheobase. (3) Further work is needed to determine whether our present findings on the AHP-firing rate relation of turtle cells generalize to the spinal neurons of other vertebrate species. (4) Relevant to point 3, substantial in vivo and in vitro work is potentially available in raw data used in reports on several mammalian and non-mammalian vertebrates. In summary, the factors in addition to the slow AHP that help determine spinal INs and MN firing rate deserve further evaluation across vertebrates, with relevant data already potentially available in several laboratories.

OBJECTIVE. We investigated the feasibility of delivering an individualized, progressive, high-repetition upper-extremity (UE) task-specific training protocol for people with stroke in the inpatient rehabilitation setting. METHOD. Fifteen patients with UE paresis participated in this study. Task-specific UE training was scheduled for 60 min/day, 4 days/wk, during occupational therapy for the duration of a participant’s inpatient stay. During each session, participants were challenged to complete ≥300 repetitions of various tasks. RESULTS. Participants averaged 289 repetitions/session, spending 47 of 60 min in active training. Participants improved on impairment and activity level outcome measures. CONCLUSION. People with stroke in an inpatient setting can achieve hundreds of repetitions of task-specific training in 1-hr sessions. As expected, all participants improved on functional outcome measures. Future studies are needed to determine whether this high-repetition training program results in better outcomes than current UE interventions.

BACKGROUND: Walking is an effective and preferred mode of exercise for older adults, yet limited evidence exists on the optimal walking intensity for frail older adults. The purpose of this study was to investigate the feasibility and efficacy of a high intensity walking training (HIWT) intervention for pre-frail and frail older adults in an assisted living facility. METHODS: Using a pre-post test design, we enrolled 5 participants aged 85–89 years who completed 12, 30-minute sessions of HIWT at 70–80% of heart rate reserve or ratings of 15 to 17 (hard to very hard) on the Rating of Perceived Exertion scale. HIWT included walking at fast speeds, directional changes, stairs, outdoor surfaces, and without an assistive device. The primary outcome was feasibility assessed through program evaluations. Secondary outcomes included frailty, self-reported health, balance, endurance, gait speed, and strength. RESULTS: HIWT is feasible in pre-frail and frail older adults. Participants viewed HIWT as highly satisfactory (mean rating 9.6/10) and 100% recommended that HIWT continue as part of the assisted living services. Participants had significant changes in frailty (p=0.001), fast gait speed (p=0.003), six minute walk test (p=0.03), and balance (p=0.01). There were no adverse events and all participants reached target training intensity in all 12 sessions. CONCLUSIONS: This study offers the first evidence of the feasibility and potential efficacy of HIWT for frail and pre-frail older adults. Initial results suggest that HIWT significantly lessens the degree of frailty, but also contributes to improved mobility and balance.

Background and Purpose. Robotic devices that provide passive guidance and stabilization of the legs and trunk during treadmill stepping may increase the delivery of locomotor training to subjects with neurological injury. Lower-extremity guidance also may reduce voluntary muscle activity as compared with compliant assistance provided by therapists. The purpose of this study was to investigate differences in metabolic costs and lower-limb muscle activity patterns during robotic- and therapist-assisted treadmill walking. Subjects. Twelve ambulatory subjects with motor incomplete spinal cord injury participated. Methods. In 2 separate protocols, metabolic and electromyographic (EMG) data were collected during standing and stepping on a treadmill with therapist and robotic assistance. During robotic-assisted walking, subjects were asked to match the kinematic trajectories of the device and maximize their effort. During therapist-assisted walking, subjects walked on the treadmill with manual assistance provided as necessary. Results. Metabolic costs and swing-phase hip flexor EMG activity were significantly lower when subjects were asked to match the robotic device trajectories than with therapist-assisted walking. These differences were reduced when subjects were asked to maximize their effort during robotic-assisted stepping, although swing-phase plantar-flexor EMG activity was increased. In addition, during standing prior to therapist- or robotic-assisted stepping, metabolic costs were higher without stabilization from the robotic device. Discussion and Conclusion. Differences in metabolic costs and muscle activity patterns between therapist- and robotic-assisted standing and stepping illustrate the importance of minimizing passive guidance and stabilization provided during step training protocols.

Locomotor training (LT) to improve walking ability in people poststroke can be accomplished with therapist assistance as needed to promote continuous stepping. Various robotic devices also have been developed that can guide the lower limbs through a kinematically consistent gait pattern. It is unclear whether LT with either therapist or robotic assistance could improve kinematic coordination patterns during walking. The purpose of this study was to determine whether LT with physical assistance as needed was superior to guided, symmetrical, robotic-assisted LT for improving kinematic coordination during walking poststroke. This study was a randomized clinical trial. Nineteen people with chronic stroke (>6 months' duration) participating in a larger randomized control trial comparing therapist- versus robotic-assisted LT were recruited. Prior to and following 4 weeks of LT, gait analysis was performed at each participant's self-selected speed during overground walking. Kinematic coordination was defined as the consistency of intralimb hip and knee angular trajectories over repeated gait cycles and was compared before and after treatment for each group. Locomotor training with therapist assistance resulted in significant improvements in the consistency of intralimb movements of the impaired limb. Providing consistent kinematic assistance during robotic-assisted LT did not result in improvements in intralimb consistency. Only minimal changes in discrete kinematics were observed in either group. The limitations included a relatively small sample size and a lack of quantification regarding the extent of movement consistency during training sessions for both groups. Coordination of intralimb kinematics appears to improve in response to LT with therapist assistance as needed. Fixed assistance, as provided by this form of robotic guidance during LT, however, did not alter intralimb coordination.

Robotic-assisted locomotor training has demonstrated some efficacy in individuals with neurological injury and is slowly gaining clinical acceptance. Both exoskeletal devices, which control individual joint movements, and elliptical devices, which control endpoint trajectories, have been utilized with specific patient populations and are available commercially. No studies have directly compared training efficacy or patient performance during stepping between devices. The purpose of this study was to evaluate kinematic, electromyographic (EMG), and metabolic responses during elliptical- and exoskeletal-assisted stepping in individuals with incomplete spinal cord injury (SCI) compared with therapist-assisted stepping. Design A prospective, cross-sectional, repeated-measures design was used. Participants with incomplete SCI (n=11) performed 3 separate bouts of exoskeletal-, elliptical-, or therapist-assisted stepping. Unilateral hip and knee sagittal-plane kinematics, lower-limb EMG recordings, and oxygen consumption were compared across stepping conditions and with control participants (n=10) during treadmill stepping. Exoskeletal stepping kinematics closely approximated normal gait patterns, whereas significantly greater hip and knee flexion postures were observed during elliptical-assisted stepping. Measures of kinematic variability indicated consistent patterns in control participants and during exoskeletal-assisted stepping, whereas therapist- and elliptical-assisted stepping kinematics were more variable. Despite specific differences, EMG patterns generally were similar across stepping conditions in the participants with SCI. In contrast, oxygen consumption was consistently greater during therapist-assisted stepping. Limitations Limitations included a small sample size, lack of ability to evaluate kinetics during stepping, unilateral EMG recordings, and sagittal-plane kinematics. Despite specific differences in kinematics and EMG activity, metabolic activity was similar during stepping in each robotic device. Understanding potential differences and similarities in stepping performance with robotic assistance may be important in delivery of repeated locomotor training using robotic or therapist assistance and for consumers of robotic devices.