Mechanical and energetic determinants of impaired gait following stroke: segmental work and pendular energy transduction during treadmill walking

Longitudinal changes in vertical stride regularity, hip flexion, and knee flexion contribute to the alteration in gait speed during hospitalization for stroke

Changes in stride regularity and joint motion during gait appear to be related to improved gait speed in hospitalized patients with stroke. We aimed to clarify the changes in stride regularity and joint motion during gait through longitudinal observations. Furthermore, we aimed to clarify the relationship between changes in gait speed, stride regularity, and joint motion during gait. Seventeen inpatients with stroke were assessed for physical and gait functions at baseline, when they reached functional ambulation category 3, and before discharge. Physical function was assessed using the Fugl-Meyer assessment for the lower extremities and the Berg Balance Scale. Gait function was assessed on the basis of gait speed, joint motion, stride regularity, and step symmetry using inertial sensors. The correlations between the ratio of change in gait speed and each indicator from baseline to discharge were analyzed. Both physical and gait functions improved significantly during the hospital stay. The ratio of change in gait speed was significantly and positively correlated with the ratio of change in vertical stride regularity (r = 0.662), vertical step symmetry (rs = 0.627), hip flexion (rs = 0.652), knee flexion (affected side) (r = 0.611), and ankle plantarflexion (unaffected side) (rs = 0.547). Vertical stride regularity, hip flexion, and knee flexion (affected side) were significant factors in determining the ratio of changes in gait speed. Our results suggest that stride regularity, hip flexion, and knee flexion could explain the entire gait cycle and that of the affected side. These parameters can be used as indices to improve gait speed.

Ipsilateral lower limb motor performance and its association with gait after stroke

BACKGROUND AND PURPOSE

Motor deficits of the ipsilateral lower limb could occur after stroke and may be associated with walking performance. This study aimed to determine whether the accuracy and movement path of targeted movement in the ipsilateral lower limb would be impaired in the chronic stage of stroke and whether this impairment would contribution to gait.

METHODS

Twenty adults with chronic stroke and 20 age-matched controls went through Mini Mental Status Examination (MMSE), and a series of sensorimotor tests. The targeted movement tasks were to place the big toe ipsilateral to the lesion at an external visual target (EXT) or a proprioceptive target (PRO, contralateral big toe) with eyes open (EO) or closed (EC) in a seated position. A motion analysis system was used to obtain the data for the calculation of error distance, deviation from a straight path, and peak toe-height during the targeted movement tasks and gait velocity, step length, step width and step length symmetry of the lower limb ipsilateral to the brain lesion during walking.

RESULTS

The stroke group had significantly lower MMSE and poorer visual acuity on the ipsilateral side, but did not differ in age or other sensorimotor functions when compared to the controls. For the targeted movement performance, only the deviation in PRO-EC showed significant between-group differences (p = 0.02). Toe-height in both EXT-EO and in PRO-EO was a significant predictor of step length (R2 = 0.294, p = 0.026) and step length symmetry (R2 = 0.359, p = 0.014), respectively.

DISCUSSION AND CONCLUSIONS

The performance of ipsilateral lower limb targeted movement could be impaired after stroke and was associated with step length and its symmetry. The training of ipsilateral targeted movement with unseen proprioceptive target may be considered in stroke rehabilitation.

Development of an assessment of bilateral locomotor efficacy for individuals post-stroke

BACKGROUND

A common framework is needed to assess walking impairments in older adults and individuals with stroke. This study develops an Assessment of Bilateral Locomotor Efficacy (ABLE) that is a straightforward indicator of walking function.

RESEARCH QUESTION

Can we develop a clinically accessible index of walking function that summarizes gait dysfunction secondary to stroke?

METHODS

The ABLE index was developed using a retrospective sample of 14 community-dwelling older adults. Data from 33 additional older adults and 105 individuals with chronic post-stroke hemiparesis were used to validate the index by factor analysis of the score components and correlation with multiple common assessments of lower extremity impairment and function.

RESULTS

The ABLE consists of four components summed for a maximum possible score of 12. The components include self-selected walking speed (SSWS), speed change from SSWS to fastest speed, non-paretic leg step length change from SSWS to fastest speed, and peak paretic leg ankle power. The ABLE revealed good concurrent validity with all recorded functional assessments. Factor analysis suggested that the ABLE measures two factors: one for forward progression and another for speed adaptability.

SIGNIFICANCE

The ABLE offers a straightforward, objective measure of walking function in adults, including individuals with chronic stroke. The index may also prove useful as a screening tool for subclinical pathology in community-dwelling older adults, but further testing is required. We encourage utilization of this index and reproduction of findings to adapt and refine the instrument for wider use and eventual clinical application.

Asymmetric cortical activation in healthy and hemiplegic individuals during walking: A functional near-infrared spectroscopy neuroimaging study

Background

This study investigated the cortical activation mechanism underlying locomotor control during healthy and hemiplegic walking.

Methods

A total of eight healthy individuals with right leg dominance (male patients, 75%; mean age, 40.06 ± 4.53 years) and six post-stroke patients with right hemiplegia (male patients, 86%; mean age, 44.41 ± 7.23 years; disease course, 5.21 ± 2.63 months) completed a walking task at a treadmill speed of 2 km/h and a functional electrical stimulation (FES)-assisted walking task, respectively. Functional near-infrared spectroscopy (fNIRS) was used to detect hemodynamic changes in neuronal activity in the bilateral sensorimotor cortex (SMC), supplementary motor area (SMA), and premotor cortex (PMC).

Results

fNIRS cortical mapping showed more SMC-PMC-SMA locomotor network activation during hemiplegic walking than during healthy gait. Furthermore, more SMA and PMC activation in the affected hemisphere was observed during the FES-assisted hemiplegic walking task than during the non-FES-assisted task. The laterality index indicated asymmetric cortical activation during hemiplegic gait, with relatively greater activation in the unaffected (right) hemisphere during hemiplegic gait than during healthy walking. During hemiplegic walking, the SMC and SMA were predominantly activated in the unaffected hemisphere, whereas the PMC was predominantly activated in the affected hemisphere. No significant differences in the laterality index were noted between the other groups and regions (p > 0.05).

Conclusion

An important feature of asymmetric cortical activation was found in patients with post-stroke during the walking process, which was the recruitment of more SMC-SMA-PMC activation than in healthy individuals. Interestingly, there was no significant lateralized activation during hemiplegic walking with FES assistance, which would seem to indicate that FES may help hemiplegic walking recover the balance in cortical activation. These results, which are worth verifying through additional research, suggest that FES used as a potential therapeutic strategy may play an important role in motor recovery after stroke.

Linking gait mechanics with perceived quality of life and participation after stroke

Background

Individuals with hemiparesis following stroke often experience a decline in the paretic limb’s anteriorly directed ground reaction force during walking (i.e., limb propulsive force). Gait speed and walking capacity have been independently associated with paretic limb propulsion, quality of life, and participation in people with stroke. However, it is unclear as to the extent that underlying limb mechanics (i.e., propulsion) play in influencing perceptions of quality of life and participation. We therefore sought to determine the role of limb propulsion during gait on the perception of quality of life and participation in people following stroke.

Methods

This study is a secondary analysis of individuals involved in a gait retraining randomized control trial. Gait speed, walking capacity, limb propulsion, Stroke Impact Scale, and average daily step counts were assessed prior to and following 6 weeks of training. The pre-training data from 40 individuals were analyzed cross-sectionally using Pearson and Spearman correlations, to evaluate the potential relationship between limb propulsion (ratio of paretic limb propulsion to total propulsion) with gait speed, gait capacity, perceived quality of life domains, and average daily step counts. Partial correlations were used to control for gait speed. Thirty-one individuals were assessed longitudinally for the same relationships.

Results

We observed a training effect for gait speed, walking capacity, and some quality of life measures. However, after controlling for gait speed, we observed no significant (p≤0.05) correlations in the cross-sectional and longitudinal analyses.

Significance

After controlling for the influence of gait speed, paretic limb propulsion is not directly related to perceived quality of life or participation. Although limb propulsion may not have a direct effect on participant’s perceived quality of life, it appears to be an important factor to enhance gait performance, and therefore may be important to target in rehabilitation, when feasible.

Thigh and Shank, Kinetic and Potential Energies during Gait Swing Phase in Healthy Adults and Stroke Survivors

Background/Problem. Given the treatment-resistant gait deficits after stroke and known elevated energy cost of gait after stroke, it is important to study the patterns of mechanical energies of the lower limb segments. There is a dearth of information regarding mechanical energies specifically for the thigh and shank across the gait cycle. Therefore, the purpose of the current work was to characterize the following: (1) relative patterns of oscillation kinetic energy (KE) and potential energy (PE) within lower limb segments and across lower limb segments in healthy adults during the swing phase at chosen and slow gait speeds; (2) KE and PE swing phase patterns and values for stroke survivors versus healthy adults walking at slow speed; and (3) KE and PE patterns during the swing phase for two different compensatory gait strategies after stroke,. Methods. This was a gait characterization study, a two-group, parallel-cohort study of fourteen stroke survivors with gait deficits, walking at <0.4 m/s and eight adults with no gait deficits. For testing, the eight healthy adults walked at their chosen speed, and then at the imposed slow speed of <0.04 m/s. We used a standard motion capture system and calculation methods to acquire, calculate, and characterize oscillation patterns of KE and PE of the limb segments (thigh and shank) across the gait cycle. Results. In healthy adults, we identified key energy conservation mechanisms inherent in the interactions of KE and PE, both within the thigh and shank segments and across those limb segments, partially explaining the low cost of energy of the normal adult chosen speed gait pattern, and the underlying mechanism affording the known minimal set of activated muscles during walking, especially during the early swing phase. In contrast, KE was effectively absent for both healthy adults at imposed slow walking speed and stroke survivors at their very slow chosen speed, eliminating the normal conservation of energy between KE and PE within the thigh and across the thigh and shank. Moreover, and in comparison to healthy adult slow speed, stroke survivors exhibited greater abnormalities in mechanical energies patterns, reflected in either a compensatory stepping strategy (over-flexing the hip) or circumducting strategy (stiff-legged gait, with knee extended throughout the swing phase). Conclusions and contribution to the field. Taken together, these findings support targeted training to restore normal balance control and normal activation and de-activation coordination of hip, knee, and ankle muscles, respectively (agonist/antagonist at each joint), so as to eliminate the known post-stroke abnormal co-contractions; this motor training is critical in order to release the limb to swing normally in response to mechanical energies and afford the use of conservation of KE and PE energies within the thigh and across thigh and shank.

Artificial Neural Network Detects Hip Muscle Forces as Determinant for Harmonic Walking in People after Stroke

Many recent studies have highlighted that the harmony of physiological walking is based on a specific proportion between the durations of the phases of the gait cycle. When this proportion is close to the so-called golden ratio (about 1.618), the gait cycle assumes an autosimilar fractal structure. In stroke patients this harmony is altered, but it is unclear which factor is associated with the ratios between gait phases because these relationships are probably not linear. We used an artificial neural network to determine the weights associable to each factor for determining the ratio between gait phases and hence the harmony of walking. As expected, the gait ratio obtained as the ratio between stride duration and stance duration was found to be associated with walking speed and stride length, but also with hip muscle forces. These muscles could be important for exploiting the recovery of energy typical of the pendular mechanism of walking. Our study also highlighted that the results of an artificial neural network should be associated with a reliability analysis, being a non-deterministic approach. A good level of reliability was found for the findings of our study.

Photobiomodulation Therapy Combined with Static Magnetic Field (PBMT–SMF) on Spatiotemporal and Kinematics Gait Parameters in Post-Stroke: A Pilot Study

Background: Gait deficit is a major complaint in patients after stroke, restricting certain activities of daily living. Photobiomodulation therapy combined with a static magnetic field (PBMT-SMF) has been studied for several diseases, and the two therapies are beneficia. However, their combination has not yet been evaluated in stroke. Therefore, for PBMT–SMF to be used more often and become an adjunctive tool in the rehabilitation of stroke survivors at physical therapy rehabilitation centers and clinics, some important aspects need to be clarified. Purpose: This study aimed to test different doses of PBMT–SMF, to identify the ideal dose to cause immediate effects on the spatiotemporal and kinematic variables of gait in post-stroke patients. Methods: A randomized, triple-blinded, placebo-controlled crossover pilot study was performed. A total of 10 individuals with hemiparesis within 6 months to 5 years since the occurrence of stroke, aged 45–60 years, were included in the study. Participants were randomly assigned and treated with a single PBMT–SMF dose (sham, 10 J, 30 J, or 50 J) on a single application, with one dose per stage at 7-day intervals between stages. PBMT–SMF was applied with a cluster of 12 diodes (4 of 905 nm laser, 4 of 875 nm LEDs, and 4 of 640 nm LEDs, SMF of 35 mT) at 17 sites on both lower limbs after baseline evaluation: plantar flexors (2), knee extensors (9), and flexors (6). The primary outcome was self-selected walking speed, and the secondary outcomes were kinematic parameters. Gait analysis was performed using SMART-D 140^® and SMART-D INTEGRATED WORKSTATION^®. The outcomes were measured at the end of each stage after the single application of each PBMT–SMF dose tested. Results: No significant differences (p > 0.05) in spatiotemporal variables were observed between the different doses, compared with the baseline evaluation. However, differences (p < 0.05) were observed in the kinematic variable of the hip in the paretic and non-paretic limbs, specifically in the minimum flexion/extension angulation during the support phase (HMST–MIN) in doses 10 J, 30 J, and 50 J. Conclusions: A single application of PBMT–SMF at doses of 10 J, 30 J, and 50 J per site of the lower limbs did not demonstrate positive effects on the spatiotemporal variables, but it promoted immediate effects in the kinematic variables of the hip (maximum and minimum flexion/extension angulation during the support phase) in the paretic and non-paretic limbs in post-stroke people.

Lower Limb Kinematic Coordination during the Running Motion of Stroke Patient: A Single Case Study

The purpose of this study was to clarify the lower limb joint motor coordination of para-athletes during running motion from frequency characteristics and to propose this as a method for evaluating their performance. The subject used was a 43-year-old male para-athlete who had suffered a left cerebral infarction. Using a three-dimensional motion analysis system, the angles of the hip, knee, and ankle joints were measured during 1 min of running at a speed of 8 km/h on a treadmill. Nine inter- and intra-limb joint angle pairs were analyzed by coherence and phase analyses. The main characteristic of the stroke patient was that there were joint pairs with absent or increased coherence peaks in the high-frequency band above 4 Hz that were not found in healthy subjects. Interestingly, these features were also observed on the non-paralyzed side. Furthermore, a phase analysis showed different phase differences between the joint motions of the stroke patient and healthy subjects in some joint pairs. Thus, we concluded there was a widespread functional impairment of joint motion in the stroke patient that has not been revealed by conventional methods. The coherence analysis of joint motion may be useful for identifying joint motion problems in para-athletes.

Targeting Paretic Propulsion and Walking Speed With a Soft Robotic Exosuit: A Consideration-of-Concept Trial

Background: Soft robotic exosuits can facilitate immediate increases in short- and long-distance walking speeds in people with post-stroke hemiparesis. We sought to assess the feasibility and rehabilitative potential of applying propulsion-augmenting exosuits as part of an individualized and progressive training program to retrain faster walking and the underlying propulsive strategy.

Methods: A 54-yr old male with chronic hemiparesis completed five daily sessions of Robotic Exosuit Augmented Locomotion (REAL) gait training. REAL training consists of high-intensity, task-specific, and progressively challenging walking practice augmented by a soft robotic exosuit and is designed to facilitate faster walking by way of increased paretic propulsion. Repeated baseline assessments of comfortable walking speed over a 2-year period provided a stable baseline from which the effects of REAL training could be elucidated. Additional outcomes included paretic propulsion, maximum walking speed, and 6-minute walk test distance.

Results: Comfortable walking speed was stable at 0.96 m/s prior to training and increased by 0.30 m/s after training. Clinically meaningful increases in maximum walking speed (Δ: 0.30 m/s) and 6-minute walk test distance (Δ: 59 m) were similarly observed. Improvements in paretic peak propulsion (Δ: 2.80 %BW), propulsive power (Δ: 0.41 W/kg), and trailing limb angle (Δ: 6.2 degrees) were observed at comfortable walking speed (p's < 0.05). Likewise, improvements in paretic peak propulsion (Δ: 4.63 %BW) and trailing limb angle (Δ: 4.30 degrees) were observed at maximum walking speed (p's < 0.05).

Conclusions: The REAL training program is feasible to implement after stroke and capable of facilitating rapid and meaningful improvements in paretic propulsion, walking speed, and walking distance.

Mechanical work as a (key) determinant of energy cost in human locomotion: recent findings and future directions

NEW FINDINGS

What is the topic of this review? This narrative review explores past and recent findings on the mechanical determinants of energy cost during human locomotion, obtained by using a mechanical approach based on König's theorem (Fenn's approach). What advances does it highlight? Developments in analytical methods and their applications allow a better understanding of the mechanical-bioenergetic interaction. Recent advances include the determination of 'frictional' internal work; the association between tendon work and apparent efficiency; a better understanding of the role of energy recovery and internal work in pathological gait (amputees, stroke and obesity); and a comprehensive analysis of human locomotion in (simulated) low gravity conditions.

ABSTRACT

During locomotion, muscles use metabolic energy to produce mechanical work (in a more or less efficient way), and energetics and mechanics can be considered as two sides of the same coin, the latter being investigated to understand the former. A mechanical approach based on König's theorem (Fenn's approach) has proved to be a useful tool to elucidate the determinants of the energy cost of locomotion (e.g., the pendulum-like model of walking and the bouncing model of running) and has resulted in many advances in this field. During the past 60 years, this approach has been refined and applied to explore the determinants of energy cost and efficiency in a variety of conditions (e.g., low gravity, unsteady speed). This narrative review aims to summarize current knowledge of the role that mechanical work has played in our understanding of energy cost to date, and to underline how recent developments in analytical methods and their applications in specific locomotion modalities (on a gradient, at low gravity and in unsteady conditions) and in pathological gaits (asymmetric gait pathologies, obese subjects and in the elderly) could continue to push this understanding further. The recent in vivo quantification of new aspects that should be included in the assessment of mechanical work (e.g., frictional internal work and elastic contribution) deserves future research that would improve our knowledge of the mechanical-bioenergetic interaction during human locomotion, as well as in sport science and space exploration.

Movement smoothness in chronic post-stroke individuals walking in an outdoor environment-A cross-sectional study using IMU sensors

Background

Walking speed is often used in the clinic to assess the level of gait impairment following stroke. Nonetheless, post-stroke individuals may employ the same walking speed but at a distinct movement quality. The main objective of this study was to explore a novel movement quality metric, the estimation of gait smoothness by the spectral arc length (SPARC), in individuals with a chronic stroke displaying mild/moderate or severe motor impairment while walking in an outdoor environment. Also, to quantify the correlation between SPARC, gait speed, motor impairment, and lower limb spasticity focused on understanding the relationship between the movement smoothness metric and common clinical assessments.

Methods

Thirty-two individuals with a chronic stroke and 32 control subjects participated in this study. The 10 meters walking test (10 MWT) was performed at the self-selected speed in an outdoor environment. The 10 MWT was instrumented with an inertial measurement unit system (IMU), which afforded the extraction of trunk angular velocities (yaw, roll, and pitch) and subsequent SPARC calculation.

Results

Movement smoothness was not influenced by gait speed in the control group, indicating that SPARC may constitute an additional and independent metric in the gait assessment. Individuals with a chronic stroke displayed reduced smoothness in the yaw and roll angular velocities (lower SPARC) compared with the control group. Also, severely impaired participants presented greater variability in smoothness along the 10 MWT. In the stroke group, a smoother gait in the pitch angular velocity was correlated with lower limb spasticity, likely indicating adaptive use of spasticity to maintain the pendular walking mechanics. Conversely, reduced smoothness in the roll angular velocity was related to pronounced spasticity.

Conclusions

Individuals with a chronic stroke displayed reduced smoothness in the yaw and roll angular velocities while walking in an outdoor environment. The quantification of gait smoothness using the SPARC metric may represent an additional outcome in clinical assessments of gait in individuals with a chronic stroke.