Biomedical subjects

Peter S Lum

Publications and source records attributed to Peter S Lum.

12 recordsLinked to original sources

PubMed2006

Activity-based therapies.

Therapeutic activity is a mainstay of clinical neurorehabilitation, but is typically unstructured and directed at compensation rather than restoration of central nervous system function. Newer activity-based therapies (ABTs) are in early stages of development and testing. The ABTs attempt to restore function via standardized therapeutic activity based on principles of experimental psychology, exercise physiology, and neuroscience. Three of the best developed ABTs are constraint-induced therapy, robotic therapy directed at the hemiplegic arm, and treadmill training techniques aimed at improving gait in persons with stroke and spinal cord injury. These treatments appear effective in improving arm function and gait, but they have not yet been clearly demonstrated to be more effective than equal amounts of traditional techniques. Resistance training is clearly demonstrated to improve strength in persons with stroke and brain injury, and most studies show that it does not increase hypertonia. Clinical trials of ABTs face several methodological challenges. These challenges include defining dosage, standardizing treatment parameters across subjects and within treatment sessions, and determining what constitutes clinically significant treatment effects. The long-term goal is to develop prescriptive ABT, where specific activities are proven to treat specific motor system disorders. Activity-based therapies are not a cure, but are likely to play an important role in future treatment cocktails for stroke and spinal cord injury.

Animals↗

PubMed2005

AutoCITE: automated delivery of CI therapy with reduced effort by therapists.

BACKGROUND AND PURPOSE: To evaluate the effectiveness of a device that automates Constraint-Induced Movement therapy (CI therapy), termed AutoCITE, when only partially supervised by therapists. METHODS: Twenty-seven participants with chronic stroke trained with AutoCITE for 3 hours per day for 10 consecutive weekdays. Participants were assigned to 1 of 3 groups in a fixed irregular order (ie, in alternating blocks): supervision from a therapist for 100%, 50%, or 25% of training time. RESULTS: The effect sizes of the treatment gains for the 3 groups on the Motor Activity Log (MAL) were very large and for the Wolf Motor Function Test they were large (all P<0.001) but were not significantly different from one another. Gains were comparable to those previously reported for participants who received an equal amount of standard one-on-one CI therapy without the device. At 1-month and long-term follow-up, gains from pretreatment on the MAL were also significant (P<0.001). CONCLUSIONS: These results demonstrate that AutoCITE training with greatly reduced supervision from a therapist is as effective as standard one-on-one CI therapy.

Activities of Daily Living↗

PubMed2005

Reliability of dynamic muscle performance in the hemiparetic upper limb.

We established reliability of upper-limb muscle performance in adults with post-stroke hemiparesis. Ten adults with post-stroke hemiparesis (51.5 +/- 34.5 months) performed isokinetic concentric shoulder flexion, elbow flexion, and extension at 3 criterion speeds (30 degrees/s, 75 degrees/s, and 120 degrees/s) on 3 separate occasions (Days 1, 7, and 49). As several participants were unable to reach criterion speeds, actual speed and power were also analyzed. Relative reliability (intraclass correlation coefficient-ICC) was excellent for torque and power (0.82 to 0.98) but less consistent for speed (0.63 to 0.99). Absolute reliability (standard error of measurement-%SEM) ranged between 0% to 34%. No systematic errors were observed across sessions. Smallest real differences (SRD) ranged between 4-11Nm for torque and 3-24W for power. Shoulder flexion, elbow flexion, and elbow extension torque, speed, and power can be measured reliably following stroke. Given that many of these individuals demonstrate inability to generate torque at preselected speeds, power may be a more valid indicator of muscle performance.

Aged↗

PubMed2004

Effects of velocity on maximal torque production in poststroke hemiparesis.

Impaired torque production is a major physical impairment following stroke, and has been studied extensively in isometric conditions. However, functional use of a limb requires torque production during movement, and the effects of velocity on maximal torque production may be abnormally enhanced in the paretic limb. The purpose of this study was to quantify the effects of movement velocity on maximal torque production during isokinetic, concentric flexion and extension of the elbow in poststroke subjects. Three speeds were tested (30, 75, 120 deg/s) over a 100-deg range of motion. To control for strength variations between subjects and limbs, isokinetic torques were normalized by peak isometric torque. As flexion velocity increased, paretic limb torque decreased at a greater rate than in the unaffected limb. During extension, paretic limb torque was much lower than torque in the unaffected limb at all speeds. In both flexion and extension, the disparity between limbs in the constant-velocity torque-angle curves became more pronounced as velocity increased. Torque decreased 44% +/- 7% in flexion and 63% +/- 9% in extension as velocity increased from 30 to 120 deg/s, whereas the corresponding decreases in the unaffected limb were only 9% +/- 5% in flexion and 16% +/- 4% in extension. No electromyographic (EMG) abnormalities were observed during flexion. During extension, EMG data provided evidence for abnormally increased antagonist coactivation in brachioradialis and markedly reduced activation in triceps as potential contributors to the decreased extension torques. The finding that movement velocity produces large deficits in maximal torque might explain why functional use of the paretic limb is often impaired even though isometric strength appears adequate.

Aged↗

PubMed2004

Evidence for improved muscle activation patterns after retraining of reaching movements with the MIME robotic system in subjects with post-stroke hemiparesis.

Previously, we reported that chronic stroke subjects had significant improvements in isometric strength, free reaching extent, and clinical evaluations of function after training in the mirror-image movement enabler (MIME) robotic device. Our primary goal in this analysis was to investigate the hypothesis that the robotic training promoted improved muscle activation patterns. To this end, we examined the interaction forces, kinematics, and electromyograms recorded during training of eight different movement patterns in active-constrained mode. In this mode, the robot constrained the reaching movements to be toward the target, and the movement velocity was proportional to the force produced along the trajectory. Thirteen chronic stroke subjects trained in MIME for 24 1-h sessions over an eight-week period. Work output was significantly increased by week five in all eight movement patterns. Low-level subjects increased their extent of reach, while high-level subjects increased their speed. Directional errors in force production were reduced in six of eight movement patterns. Electromyographic data provided evidence for improved muscle activation patterns in the four movement patterns that started at tabletop level and ended at shoulder level. In contrast, there was no evidence of improved muscle activation patterns in any of the tabletop movements, with increased activation of antagonists in two movement patterns. This dichotomy may have been related to compensation at the shoulder girdle during movements that remained at tabletop level. A simple biomechanical model will be introduced to demonstrate the likelihood of this possibility.

Arm↗

PubMed2004

Automated Constraint-Induced Therapy Extension (AutoCITE) for movement deficits after stroke.

We report progress in the development of AutoCITE, a workstation that delivers the task practice component of upper-limb Constraint-Induced Movement therapy and that can potentially be used in the clinic or the home without the need for one-on-one supervision from a therapist. AutoCITE incorporates a computer and eight task devices arranged on a modified cabinet. Task performance is automatically recorded, and several types of feedback are provided. In preliminary testing, nine chronic stroke subjects with mild to moderate motor deficits practiced with AutoCITE for 3 h each weekday for 2 weeks. Subjects wore a padded mitt on the less-affected hand for a target of 90% of their waking hours. In terms of effect sizes, gains were large and significant on the Motor Activity Log, and moderate to large on the Wolf Motor Function Test. These gains were comparable to the gains of a matched group of 12 subjects who received standard Constraint-Induced Movement therapy.

Adult↗

PubMed2003

Evidence for strength imbalances as a significant contributor to abnormal synergies in hemiparetic subjects.

Abnormal synergies in the paretic shoulder and elbow of hemiparetic subjects were quantified during maximal voluntary contractions (MVCs) in 27 subjects with a history of stroke and 8 age-matched control subjects. A six-axis load cell allowed simultaneous measurement of the primary torque the subject was attempting to maximize and the secondary torques at other joint actions. For example, during MVC of shoulder flexion, shoulder flexion is the primary torque and the secondary torques are internal/external rotation, abduction/adduction, and elbow flexion/extension. In general, the stroke subjects had increased secondary torques compared to controls, resulting in abnormal joint torque coupling within the set consisting of elbow flexion, internal rotation, adduction, shoulder flexion. Unlike previous studies, abnormal secondary torques in several cases were due to strength imbalances, which occur when the strength deficit for a particular joint action is greater than the strength deficit in the opposite joint action. This hypothesis was supported by electromyographic recordings and by the finding that subjects with larger strength imbalances tended to produce larger secondary torques. Possible mechanisms and consequences for rehabilitative treatments are discussed.

Aged↗

PubMed2002

Robot-assisted movement training compared with conventional therapy techniques for the rehabilitation of upper-limb motor function after stroke.

OBJECTIVE: To compare the effects of robot-assisted movement training with conventional techniques for the rehabilitation of upper-limb motor function after stroke. DESIGN: Randomized controlled trial, 6-month follow-up. SETTING: A Department of Veterans Affairs rehabilitation research and development center. PARTICIPANTS: Consecutive sample of 27 subjects with chronic hemiparesis (>6mo after cerebrovascular accident) randomly allocated to group. INTERVENTIONS: All subjects received twenty-four 1-hour sessions over 2 months. Subjects in the robot group practiced shoulder and elbow movements while assisted by a robot manipulator. Subjects in the control group received neurodevelopmental therapy (targeting proximal upper limb function) and 5 minutes of exposure to the robot in each session. MAIN OUTCOME MEASURES: Fugl-Meyer assessment of motor impairment, FIMtrade mark instrument, and biomechanic measures of strength and reaching kinematics. Clinical evaluations were performed by a therapist blinded to group assignments. RESULTS: Compared with the control group, the robot group had larger improvements in the proximal movement portion of the Fugl-Meyer test after 1 month of treatment (P<.05) and also after 2 months of treatment (P<.05). The robot group had larger gains in strength (P<.02) and larger increases in reach extent (P<.01) after 2 months of treatment. At the 6-month follow-up, the groups no longer differed in terms of the Fugl-Meyer test (P>.30); however, the robot group had larger improvements in the FIM (P<.04). CONCLUSIONS: Compared with conventional treatment, robot-assisted movements had advantages in terms of clinical and biomechanical measures. Further research into the use of robotic manipulation for motor rehabilitation is justified.

Aged↗

PubMedDate not supplied

Reliability and responsiveness of elbow trajectory tracking in chronic poststroke hemiparesis.

This study established the reliability of a novel upper-limb trajectory-tracking task for assessment of perceptual motor control in hemiparetic adults. Eleven persons with chronic poststroke hemiparesis (mean 58.6 months) and eleven nondisabled control subjects performed an elbow flexion-extension task against a low-resistance isotonic load at three speeds: 25 degrees/s, 45 degrees/s, and 65 degrees/s. Both arms (paretic and nonparetic or dominant and nondominant) were tested during two identical sessions separated by 1 week. Relative reliability (intraclass correlation coefficient [ICC]) ranged from 0.5 to 0.8 and absolute reliability (standard error of measurement [SEM%]) ranged between 19% to 36% across both subject groups. No systematic errors between test sessions were revealed. Smallest real differences (SRDs) were determined to be +/- 2 degrees to 3 degrees in nondisabled, +/- 2 degrees to 5 degrees in nonparetic and +/- 9 degrees in paretic arms. Responsiveness ratios derived with the use of the SRDs ranged between 1.91 to 2.45, indicating that this instrument is sensitive to clinically important change and suitable for demonstrating effects on upper-limb motor performance following clinical intervention.

Aged↗

PubMedDate not supplied

A telerehabilitation approach to delivery of constraint-induced movement therapy.

We have developed a device called AutoCITE (Automated Constraint-Induced Therapy Extension) that automates the intensive training component of constraint-induced (CI) movement therapy, also known as CI therapy. This study evaluated the effectiveness of AutoCITE training in a telerehabilitation setting when supervised remotely and with only intermittent interaction with a therapist. Seven participants with chronic stroke trained with AutoCITE for 3 h/d for 10 consecutive weekdays. The therapist supervised the training from a different room in the clinic using remote control of the AutoCITE computer and teleconferencing equipment when needed. Treatment gains on the Motor Activity Log were quite large (p < 0.001, d' = 3), while gains on the Wolf Motor Function Test and the Jebsen-Taylor Hand Function Test were large (p < 0.05, d' > 0.9). Gains were comparable in size with those previously reported for participants who received equal intensities of directly supervised AutoCITE training or standard one-on-one CI therapy without the device.

Activities of Daily Living↗

PubMedDate not supplied

MIME robotic device for upper-limb neurorehabilitation in subacute stroke subjects: A follow-up study.

This study presents results from a randomized controlled clinical trial of the Mirror Image Movement Enabler (MIME) robotic device for shoulder and elbow neurorehabilitation in subacute stroke patients, including data on the use of its bilateral training mode. MIME incorporates a PUMA 560 robot (Staubli Unimation Inc, Duncan, South Carolina) that applies forces to the paretic limb during unilateral and bilateral movements in three dimensions. Robot-assisted treatment (bilateral, unilateral, and combined bilateral and unilateral) was compared with conventional therapy. Similar to a previous study in chronic stroke, combined unilateral and bilateral robotic training had advantages compared with conventional therapy, producing larger improvements on a motor impairment scale and a measure of abnormal synergies. However, gains in all treatment groups were equivalent at the 6-month follow-up. Combined unilateral and bilateral training yielded functional gains that were similar to the gains from equivalent doses of unilateral-only robotic training, although the combined group had more hypertonia and less movement out of synergy at baseline. Robot-assisted treatment gains exceeded those expected from spontaneous recovery. These results are discussed in light of the need for further device development and continued clinical trials.

Acute Disease↗

PubMedDate not supplied

Robot-assisted movement training for the stroke-impaired arm: Does it matter what the robot does?

Robot-assisted movement training improves arm movement ability following acute and chronic stroke. Such training involves two interacting processes: the patient trying to move and the robot applying forces to the patient's arm. A fundamental principle of motor learning is that movement practice improves motor function; the role of applied robotic forces in improving motor function is still unclear. This article reviews our work addressing this question. Our pilot study using the Assisted Rehabilitation and Measurement (ARM) Guide, a linear robotic trainer, found that mechanically assisted reaching improved motor recovery similar to unassisted reaching practice. This finding is inconclusive because of the small sample size (n = 19), but suggest that future studies should carefully control the amount of voluntary movement practice delivered to justify the use of robotic forces. We are optimistic that robotic forces will ultimately show additional therapeutic benefits when coupled with movement practice. We justify this optimism here by comparing results from the ARM Guide and the Mirror Image Movement Enabler robotic trainer. This comparison suggests that requiring a patient to generate specific patterns of force before allowing movement is more effective than mechanically completing movements for the patient. We describe the engineering implementation of this "guided-force training" algorithm.

Algorithms↗