Brenda L. Davies

Neurorehabilitation Strategies Focusing on Ankle Control Improve Mobility and Posture in Persons With Multiple Sclerosis.

Background and Purpose: The neuromuscular impairments seen in the ankle plantarflexors have been identified as a primary factor that limits the mobility and standing postural balance of individuals with multiple sclerosis (MS). However, few efforts have been made to find effective treatment strategies that will improve the ankle plantarflexor control. Our objective was to determine whether an intensive 14-week neurorehabilitation protocol has the potential to improve the ankle plantarflexor control of individuals with MS. The secondary objectives were to determine whether the protocol would also improve postural control, plantarflexion strength, and mobility. Methods: Fifteen individuals with MS participated in a 14-week neurorehabilitation protocol, and 20 healthy adults served as a comparison group. The primary measure was the amount of variability in the submaximal steady-state isometric torque, which assessed plantarflexor control. Secondary measures were the Sensory Organization Test composite score, maximum plantarflexion torque, and the spatiotemporal gait kinematics. Results: There was less variability in the plantarflexion torques after the neurorehabilitation protocol (preintervention, 4.15% ± 0.5%; postintervention, 2.27% ± 0.3%). In addition, there were less postural sway (preintervention, 51.87 ± 0.2 points; postintervention, 67.8 ± 0.5 points), greater plantarflexion strength (preintervention, 0.46 ± 0.04 Nm/kg; postintervention, 0.57 ± 0.05 Nm/kg), and faster walking speeds (preferred preintervention, 0.71 ± 0.05 m/s; preferred postintervention, 0.81 ± 0.05 m/s; fast-as-possible preintervention, 0.95 ± 0.06 m/s; postintervention, 1.11 ± 0.07 m/s). All of the outcome variables matched or trended toward those seen in the controls. Discussion and Conclusions: The outcomes of this exploratory study suggest that the neurorehabilitation protocol employed in this investigation has the potential to promote clinically relevant improvements in the ankle plantarflexor control, standing postural balance, ankle plantarflexion strength, and the mobility of individuals with MS. Video Abstract available for more insights from the authors (see Video, Supplemental Digital Content 1, http://links.lww.com/JNPT/A110).

Children with cerebral palsy have greater stochastic features present in the variability of their gait kinematics.

Children with CP have a more variable gait pattern. However, it is currently unknown if these variations arise from deterministic variations that are a result of a change in the motor command or stochastic features that are present in the nervous system. The aim of this investigation was to use a Langevin equation methodology to evaluate the deterministic and stochastic features that are present in the variability of the gait kinematics of children with cerebral palsy (CP). Ten children with spastic diplegic CP and nine typically developing (TD) children participated in this investigation. All of the children walked on a treadmill for 2 min while a three-dimensional motion capture system recorded the step kinematics. Our major findings for this investigation were: (1) children with CP had greater variability in their gait patterns than TD children, (2) the variability of the children with CP and TD children had similar deterministic features, (3) the variability had greater stochastic features for the children with CP, and (4) the increase in the amount of variability was strongly correlated with the increase in stochastic features. These results indicate that the variability seen in the gait patterns of children with CP may be due to the inability to suppress the noise that is present in the neuromuscular system.

Multiple sclerosis influences the precision of the ankle plantarflexon muscular force production.

OBJECTIVE To quantify the precision of the steady-state isometric control of the ankle plantarflexors musculature of individuals with multiple sclerosis (MS), and to evaluate if the precision is related to the mobility impairments. METHODS Individuals with MS and healthy adults performed a submaximal steady-state isometric contraction with the ankle plantarflexors. The coefficient of variation was used to assess the amount of variability or error in the precision of the torques generated by the ankle plantarflexor musculature. The participants also walked across a digital mat at their preferred and fast-as-possible walking speeds, which recorded their spatiotemporal gait kinematics. RESULTS The individuals with MS: (1) had reduced maximal voluntary torques at the ankle, (2) a greater amount of variability in the precision of the isometric ankle torques, (3) altered and more variable spatiotemporal gait kinematics, and (4) a greater amount of variability in the isometric ankle torques were related to a slower walking speed and cadence, shorter step length and a greater amount of gait variability. CONCLUSIONS These results further fuels the impression that a reduction in control of the ankle joint musculature may be a key factor in the mobility and balance impairments seen in individuals with MS.

Errors in the ankle plantarflexor force production are related to the gait deficits of individuals with multiple sclerosis

BACKGROUND Individuals with multiple sclerosis (MS) often have limited mobility that is thought to be due to the neuromuscular impairments of the ankle. Greater isometric motor control of the ankle has been associated with better standing postural balance but its relationship to mobility is less understood. The objectives of this investigation were to quantify the motor control of the ankle plantarflexors of individuals with MS during a dynamic isometric motor task, and explore the relationship between the ankle force control and gait alterations. METHODS Fifteen individuals with MS and 15 healthy adults participated in both a dynamic isometric ankle plantarflexion force matching task and a biomechanical gait analysis. FINDINGS Our results displayed that the subjects with MS had a greater amount of error in their dynamic isometric force production, were weaker, walked with altered spatiotemporal kinematics, and had reduced maximal ankle moment at toe-off than the control group. The greater amount of error in the dynamic force production was related to the decreases in strength, step length, walking velocity, and maximal ankle moment during walking. INTERPRETATION Altogether these results imply that errors in the ankle plantarflexion force production may be a limiting factor in the mobility of individuals with MS.

Individuals with multiple sclerosis redistribute positive mechanical work from the ankle to the hip during walking

Individuals with multiple sclerosis (MS) typically walk slower, have reduced cadences and shorter step lengths. While these spatiotemporal gait alterations have been thought to be due to decreased power generation at the ankle, the distribution of mechanical work across the ankle, knee and hip joints during walking is not well understood. By quantifying the mechanical work at each joint, the compensatory mechanisms utilized by individuals with MS to maintain gait speed may be better understood. Fifteen subjects with MS (EDSS: 4.4±1.0) and fifteen healthy age-matched control subjects completed a three-dimensional gait analysis. The net mechanical work at the ankle, knee and hip joints was quantified for the stance phase of gait. Our results found that the less impaired leg of the subjects with MS generated a similar amount of mechanical work as the control group; however, the ankle joint produced less positive mechanical work, and the hip joint generated more positive mechanical work. Additionally, the less impaired leg of the subjects with MS and the leg of the control group generated more positive work than the more impaired leg of the subjects with MS. These outcomes suggest that individuals with MS may adopt a hip compensatory strategy with their less impaired leg during gait due to the limited amount of mechanical work generated at the ankle.

Two Different Types of High-Frequency Physical Therapy Promote Improvements in the Balance and Mobility of Persons With Multiple Sclerosis

OBJECTIVE To evaluate the mobility and postural balance improvements that could be achieved in a cohort of persons with multiple sclerosis (MS) who participated in a motor adaptation protocol and a cohort of persons with MS who participated in a therapeutic exercise protocol. DESIGN A cohort design, where subjects were evaluated before and after a 6-week intervention period. SETTING Clinical laboratory setting. PARTICIPANTS Individuals (N=42) with relapsing-remitting or secondary progressive MS (Expanded Disability Status Scale [EDSS] scores, 3.0-6.5) were initially screened for eligibility for participation in the study, from which those who fit the inclusion criteria (n=32) were enrolled in the study. Subjects were pseudorandomly assigned to a treatment group and matched based on EDSS scores. Fourteen individuals in the motor adaptation cohort (MAC) (mean age ± SD, 52.6±9y; mean EDSS score ± SD, 5.5±0.9) and 13 individuals in the therapeutic exercise cohort (TEC) (mean age ± SD, 54.0±9y; mean EDSS score ± SD, 5.3±0.9) completed the entire duration of their respective programs. INTERVENTIONS Both cohorts completed their therapy twice a day, 5 days each week, for 6 weeks. Each session of the MAC program consisted of balance and gait training that encouraged new ways to adapt to challenging task demands. The TEC program was similar to a traditional exercise program. MAIN OUTCOME MEASURES The Sensory Organization Test, 6-minute walk test, and gait spatiotemporal kinematics. RESULTS Collectively, both treatment groups had improvements in postural balance (P=.001), walking endurance (P=.002), walking speed (P=.004), and step length (P<.001) after therapy. However, there were no statistical differences between the 2 treatment groups for any of the outcome variables (P values >.01). CONCLUSIONS Our exploratory results suggest that a high frequency of physical therapy rather than a specific activity focus might be an important parameter for persons with MS.

Age-related differences in the motor planning of a lower leg target matching task

While the development and execution of upper extremity motor plans have been well explored, little is known about how individuals plan and execute rapid, goal-directed motor tasks with the lower extremities. Furthermore, the amount of time needed to integrate the proper amount of visual and proprioceptive feedback before being able to accurately execute a goal-directed movement is not well understood; especially in children. Therefore, the purpose of this study was to initially interrogate how the amount of motor planning time provided to a child before movement execution may influence the preparation and execution of a lower leg goal-directed movement. The results displayed that the amount of pre-movement motor planning time provided may influence the reaction time and accuracy of a goal directed leg movement. All subjects in the study had longer reaction times and less accurate movements when no pre-movement motor planning time was provided. In addition, the children had slower reaction times, slower movements, and less accurate movements than the adults for all the presented targets and motor planning times. These results highlight that children may require more time to successfully plan a goal directed movement with the lower extremity. This suggests that children may potentially have less robust internal models than adults for these types of motor skills.

The Stochastic Component of the Postural Sway Variability is Higher in Children with Balance Impairments

Children with balance impairments have an increased amount of variability in the sway of the center of pressure (COP) during standing. Limited efforts have been made to quantify the nature of the variability. This exploratory investigation examined the deterministic and stochastic features that comprise the time-dependent postural sway variability during standing. We measured the COP in standing of a heterogeneous group of children with balance impairments and an age-matched cohort of typically developing children, both with and without vision. The standard deviation of the COP was used to quantify the amount of variability present in the postural sway. A Langevin equation methodology was additionally employed to reconstruct the deterministic and stochastic features that comprised the postural sway variability. Our experiment resulted in three key findings: (1) removal of visual information increased the stochastic features of the postural sway variability, (2) the stochastic features were greater for the children with balance impairments, (3) the change in the amount of variability was strongly correlated with change the stochastic features. These results imply that the inability to suppress the stochastic features present in the nervous system may play a prominent role in the balance problems of children. Moreover, our results imply that alterations in the stochastic features drive the postural system away from successful balance strategies.

Impaired anticipatory vision and visuomotor coordination affects action planning and execution in children with hemiplegic cerebral palsy

BACKGROUND Action-planning and execution deficits in children with hemiplegic cerebral palsy (HCP) are potentially due to deficits in the integration of sensory information, such as vision, with motor output. AIMS To determine differences in anticipatory visual patterns in children with HCP compared to typically developing (TD) children, and to assess visuomotor coordination in children with HCP. METHODS AND PROCEDURES We included 13 children with HCP (Age = 6.8 + 2.9 yrs) and 15 TD children (Age = 5.8 + 1.1 yrs). The experimental task used in this study is a valid action-planning task, which consisted of initially reaching and grasping an object placed at a fixed position, followed by placing the object in a random target position. Visual patterns were recorded using a head-mounted eye-tracker system and arm movements were recorded using motion capture (120 Hz). OUTCOMES AND RESULTS Children with HCP had delayed anticipatory gaze time and longer latency than TD children during the planning and execution phases. Children with HCP also had a higher frequency of gaze shifts, longer reaction times (RT) and movement times (MT) than TD children. CONCLUSIONS AND IMPLICATIONS Children with HCP may have deficits in anticipatory vision, which potentially affected planning and executing a goal-directed action. Therapeutic interventions focusing on improving visuomotor coordination may improve the motor performance in children with HCP.

Dissipation of disturbances seen in the knee joint kinematics of children with cerebral palsy.

PURPOSE Children with cerebral palsy (CP) often use a crouch gait pattern that has disturbances in the knee joint kinematics. Although the length and rate of lengthening of the hamstring musculature have been speculated to be the reason that these disturbances are not adequately dissipated, this relationship has not been adequately explored. The purpose of this exploratory investigation was to use simulations of a musculoskeletal model and Floquet analysis to evaluate how the performance of hamstrings musculature during gait may be related to the knee joint instabilities seen in children with CP. METHODS Children with CP and typically developing (TD) children walked on a treadmill as a motion capture system assessed the knee joint kinematics. Floquet analysis was used to quantify the rate that disturbances present at the knee joint were dissipated, and simulations of a musculoskeletal model were used to estimate the in vivo length and velocity of the hamstrings. Pearson correlation coefficients were calculated to determine if there was a relationship between the rate that the disturbances were dissipated and the performance of the hamstring musculature. RESULTS The children with CP had hamstrings that lengthened more slowly than TD children, and required more strides to dissipate disturbances in the knee joint kinematics. There was negative correlation between the rate that the hamstrings lengthened and the rate that the knee joint disturbances were dissipated. CONCLUSIONS Our results suggest that the ability of children with CP to dissipate the knee joint disturbances may be related to the inability to properly control the hamstring musculature.