Sandra J. Olney

Hemiparetic gait following stroke. Part I : Characteristics

Abstract The biomechanical patterns that characterize the gait of persons who have sustained a stroke are reviewed. Reduced walking speed and longer stance phases, greater on the unaffected side, are reported. Variations in joint excursions include several deviations at initial contact and reduced excursions during swing. Electromyographic patterns have provided a classification method. Joint moment reports were variable, but included high hip flexor moments in late stance, positively related to speed. The muscle groups of the unaffected side performed about 60% of the work of walking across speeds. Commonly occurring gait deviations resulting from particular impairments or adaptations to impairments are identified.

Muscle strengthening and physical conditioning to reduce impairment and disability in chronic stroke survivors

OBJECTIVE To evaluate the impact of a program of muscle strengthening and physical conditioning on impairment and disability in chronic stroke subjects. DESIGN A randomized pretest and posttest control group, followed by a single-group pretest and posttest design. SUBJECTS Thirteen community-dwelling stroke survivors of at least 9 months. INTERVENTION A 10-week (3 days/week) program consisting of a warm-up, aerobic exercises, lower extremity muscle strengthening, and a cool-down. MAIN OUTCOME MEASURES Peak isokinetic torque of the major muscle groups of the affected lower limb, quadriceps and ankle plantarflexor spasticity, gait speed, rate of stair climbing, the Human Activity Profile (HAP), and the Nottingham Health Profile (NHP) were recorded twice for the treatment group and three times for the control group. RESULTS Significant improvements were found for all the selected outcome measures (HAP, NHP, and gait speed) for the treatment group (p < .001). In terms of overall training effects, the 13 subjects demonstrated increases in strength of the affected major muscle groups, in HAP and NHP profiles, and in gait speed and rate of stair climbing without concomitant increases in either quadriceps or ankle plantarflexor spasticity. CONCLUSIONS The 10-week combined program of muscle strengthening and physical conditioning resulted in gains in all measures of impairment and disability. These gains were not associated with measurable changes of spasticity in either quadriceps or ankle plantarflexors.

Predictions of knee and ankle moments of force in walking from EMG and kinematic data

A deterministic model was developed and validated to calculate instantaneous ankle and knee moments during walking using processed EMG from representative muscles, instantaneous joint angle as a correlate of muscle length and angular velocity as a correlate of muscle velocity, and having available total instantaneous joint moments for derivation of certain model parameters. A linear regression of the moment on specifically processed EMG, recorded while each subject performed cycled isometric calibration contractions, yielded the constants for a basic moment-EMG relationship. Using the resultant moment for optimization, the predicted moment was proportionally augmented for longer muscle lengths and reduced for shorter lengths. Similarly, the predicted moment was reduced for shortening velocities and increased if the muscle was lengthening. The plots of moments predicted using the full model and those calculated from link segment mechanics followed each other quite closely. The range of root mean square errors were: 3.2-9.5 Nm for the ankle and 4.7-13.0 Nm for the knee.

Effects of muscle strengthening and physical conditioning training on temporal, kinematic and kinetic variables during gait in chronic stroke survivors.

The purpose of this study was to evaluate the impact of a combined program of muscle strengthening and physical conditioning on gait performance in subjects with chronic stroke, using a single group pre- and post-test design. Thirteen subjects were recruited for the 10-week program (3 days/week), which consisted of warm-up, aerobic exercises, lower extremity muscle strengthening and cool-down. Data from cinematographic film and a force plate obtained during multiple walking trials were used in a four-segment kinetic model to yield spatiotemporal, kinematic and kinetic variables. Gait analysis revealed that the 10 week training resulted in significant increases in gait speed associated with improvements in walking patterns as determined by increases in selected kinematic and kinetic measures. After training, subjects were able to generate higher levels of powers and demonstrated increases in positive work performed by the ankle plantar flexor and hip flexor/extensor muscles.

Kinematic, kinetic and metabolic parameters of treadmill versus overground walking in healthy older adults

BACKGROUND Although treadmill and overground walking appear to be biomechanically similar in healthy, young adults it is not known whether this can be generalized to older subjects or if the metabolic demands are correspondingly comparable. METHODS Ten healthy adults between 50 and 73 years of age walked at the same speed overground and on a treadmill. Temporal parameters, angular kinematics and vertical ground reaction forces were recorded during walking once subjects were in steady state as determined from their heart rate and oxygen uptake. FINDINGS Step, stride and joint angular kinematics were similar for both modes of walking with the exception of the maximum hip flexion and knee extension which were more pronounced with treadmill or overground walking, respectively but in both instances differed by less than 3 degrees. Vertical ground reaction force profiles were similar although the peak associated with push-off was 5.5% smaller with treadmill walking. The metabolic requirements of treadmill walking were about 23% higher than that associated with overground walking. INTERPRETATION While treadmill and overground walking are biomechanically similar, the metabolic cost of treadmill walking is higher. Clinically this may be important when using a treadmill for gait retraining in patient populations as it may lead to premature fatigue or undesirable physiologic challenge.

Effect of a Home Program of Hip Abductor Exercises on Knee Joint Loading, Strength, Function, and Pain in People With Knee Osteoarthritis: A Clinical Trial

Background Hip abductor muscle weakness may result in impaired frontal-plane pelvic control during gait, leading to greater medial compartment loading in people with knee osteoarthritis (OA). Objective This study investigated the effect of an 8-week home strengthening program for the hip abductor muscles on knee joint loading (measured by the external knee adduction moment during gait), strength (force-generating capacity), and function and pain in individuals with medial knee OA. Design The study design was a nonequivalent, pretest-posttest, control group design. Setting Testing was conducted in a motor performance laboratory. Patients An a priori sample size calculation was performed. Forty participants with knee OA were matched for age and sex with a control group of participants without knee OA. Intervention Participants with knee OA completed a home hip abductor strengthening program. Measurements Three-dimensional gait analysis was performed to obtain peak knee adduction moments in the first 50% of the stance phase. Isokinetic concentric strength of the hip abductor muscles was measured using an isokinetic dynamometer. The Five-Times-Sit-to-Stand Test was used to evaluate functional performance. Knee pain was assessed with the Western Ontario and McMaster Universities Osteoarthritis Index questionnaire. Results Following the intervention, the OA group demonstrated significant improvement in hip abductor strength, but not in the knee adduction moment. Functional performance on the sit-to-stand test improved in the OA group compared with the control group. The OA group reported decreased knee pain after the intervention. Limitations Gait strategies that may have affected the knee adduction moment, including lateral trunk lean, were not evaluated in this study. Conclusions Hip abductor strengthening did not reduce knee joint loading but did improve function and reduce pain in a group with medial knee OA.

Hemiparetic gait following stroke. Part II: Recovery and physical therapy

Abstract This part begins with a review of locomotor recovery following stroke as revealed by clinical measures. These describe a recovery curve with a rapid rise within the first 6 weeks when active rehabilitation procedures supplement natural recovery, followed by a more gradual rise thereafter to plateau at about 6 months after stroke. The sensitivity of these clinical measures is questioned for more advanced stages of recovery since gait velocity and other quantitative EMG and movement variables reveal changes indicative of recovery up to 2 years after stroke. A review is then made, from the traditional to the most recent, of physical-therapy approaches used to promote locomotor recovery. Therapy choice for different types of disturbed motor control is briefly discussed. The need for the development of new therapeutic strategies based on current science is emphasized as is the use of sensitive outcome measures and appropriate study designs to evaluate therapy efficacy.

A comparison of gait biomechanics and metabolic requirements of overground and treadmill walking in people with stroke.

BACKGROUND Comparisons of treadmill and overground walking following stroke indicate that symmetry in temporal-distance measures is better on the treadmill suggestive of better gait economy. We examined this issue by examining the kinematic, kinetic and metabolic demands associated with overground and treadmill walking at matched speeds and also explored the effect of increasing treadmill speed. METHODS Ten people with hemiparesis walked overground at their preferred speed which was matched on the treadmill. Belt speed was then increased 10% and 20% above preferred speed. Temporal-distance outcomes, angular kinematics and vertical ground reaction forces were recorded during steady state (stable heart rate and oxygen uptake). FINDINGS Step and stance times were longer when walking overground but the degree of symmetry was comparable for both surfaces. In contrast kinematic data revealed significant interlimb asymmetry with respect to all lower limb joint excursions during overground walking accompanied by higher vertical ground reaction forces at push-off. The metabolic demands, however, were lower when walking overground than on the treadmill. Increasing the belt speed increased angular displacements and the vertical forces associated with both limbs such that symmetry remained unchanged. Metabolic demands increased significantly. INTERPRETATION People with stroke adopt a more symmetrical kinematic walking pattern on the treadmill which is maintained at faster belt speeds. Surprisingly, at matched speed the metabolic cost was significantly higher with treadmill walking. We suggest further research to explore whether an increased reliance on the hip musculature to compensate lower push-off forces could explain the higher the energy cost.

Role of symmetry in gait performance of stroke subjects with hemiplegia

Abstract This study examined the symmetry properties of 34 gait variables in a group of 31 hemiplegic subjects. A variable was called symmetric if subjects with the highest speeds had equal values on both sides of the body. If the highest speeds were achieved when the values of the affected side exceeded the unaffected, the variable was called asymmetric. Correlations of the differences and absolute differences with speed were used to detect symmetric and asymmetric variables, as well as variables exhibiting other forms of symmetry. Seven variables were detected but only one showed symmetry itself. Four asymmetric variables and three variables with other symmetry properties were identified. In summary there is only weak evidence that symmetry plays any role in promoting speed in this subject group; in fact asymmetric variables seem more important.

Mechanical factors relate to pain in knee osteoarthritis.

BACKGROUND Pain experienced by people with knee osteoarthritis is related to psychosocial factors and damage to articular tissues and/or the pain pathway itself. Mechanical factors have been speculated to trigger this pain experience; yet mechanics have not been identified as a source of pain in this population. The purpose of this study was to identify whether mechanics could explain variance in pain intensity in people with knee osteoarthritis. METHODS Data from 53 participants with physician-diagnosed knee osteoarthritis (mean age=68.5 years; standard deviation=8.6 years) were analyzed. Pain intensity was reported on the Western Ontario and McMaster Universities Osteoarthritis Index. Mechanical measures included weight-bearing varus-valgus alignment, body mass index and isokinetic quadriceps torque. Gait analysis captured the range of adduction-abduction angle, range of flexion-extension angle and external knee adduction moment during level walking. FINDINGS Pain intensity was significantly related to the dynamic range of flexion-extension during gait and body mass index. A total of 29% of the variance in pain intensity was explained by mechanical variables. The range of flexion-extension explained 18% of variance in pain intensity. Body mass index added 11% to the model. The knee adduction moment was unrelated to pain intensity. INTERPRETATION The findings support that mechanical factors are related to knee osteoarthritis pain. Because limitations in flexion-extension range of motion and body size are modifiable factors, future research could examine whether interventions targeting these mechanics would facilitate pain management.