Evaluation of Lower Limb Neuromuscular System Observability and Estimability of Muscle Activity

Abstract

In this work, we describe a method for estimating the muscle activity without drawing any assumptions regarding optimality principles in human motor control strategies; further, the method does not require any neural circuitry modeling which limits the neurophysiological terms and estimability of the method. We introduce the concept of system observability, which can reconstruct states from outputs and their derivatives based on system dynamics. Based on neuromuscular system observability, we estimate the muscle activity from joint torques and kinematics of multiple locomotive gaits, while considering the unknown neural inputs as system disturbances. Moreover, to quantify the robustness of the method, the degree of observability and parameter sensitivity are evaluated. Finally, the neurophysiological implications and generality of the method are addressed.     

Sleep dependent consolidation of gross motor sequence learning with motor imagery

Acquisition of gross motor sequence learning with physical and mental training elicits gains in performance. However, the effects of sleep or daytime consolidation after both types of practice remain unclear, especially the effects upon the goal- and movement-based components of a gross motor sequential task. The main purpose of this study was to test the effect of physical practice (PP) and motor imagery practice (MIP) on the acquisition and consolidation processes of gross motor sequence learning.Seventy-six participants were tested before and after PP or MIP on a whole-body sequential paradigm, following either a night of sleep (PP_sleep and MIP_sleep groups) or an equivalent daytime period (PP_day and MIP_day groups). Control groups without training were tested following similar timespans (CTRL_sleep and CTRL_day groups). The number of sequential movements and the centre of mass displacement – corresponding to goal and movement-based components, respectively – were assessed.Results showed that relative to the CTRL groups, the PP and MIP groups improved performance during acquisition. Importantly, only the MIP_sleep group further improved performance after a night of sleep; participants of other groups stabilised their performance after consolidation. Additionally, the number of sequential movements and the centre of mass displacement evolved conjointly without being influenced by the type of training or the nature of the consolidation.To conclude, these results confirm that sleep contributes to the consolidation of gross motor sequence learning acquired with MIP but not PP. The relationship between the goal- and movement-based components of a gross motor sequential task is discussed.     

The effect of augmented feedback on the performance and learning of gross motor and sport-specific skills: A systematic review

BackgroundAugmented feedback is often provided by coaches and practitioners as a method to enhance the performance of athletes and learners. When implementing a feedback intervention, it is important to assess the expertise of the learner and the complexity of the skill, to ensure an appropriate feedback modality, frequency, and timing is provided. However, researchers have a limited understanding of how these variables interact to influence the performance and learning of gross motor and sport-specific skills.ObjectivesThe purpose of this systematic review was to examine the effects of augmented feedback on the performance and learning of gross motor and sport-specific skills in an adult population.MethodsA systematic literature search was conducted on electronic databases, PubMed, Web of Science and PsycINFO, from inception to March 2020, with a revised search completed to January 2022. The search terms used were related to augmented feedback and motor performance and learning. Studies were included if they consisted of a randomised control trial with pre- and retention-testing measures, which investigated an AF intervention on a gross motor and/or sport-specific skill in a healthy adult population. Risk of bias was assessed using the revised Cochrane risk-of-bias tool for randomised trials (RoB2).ResultsTwenty-four studies were included, with a total of 895 participants. Most studies reported a learning improvement following the provision of AF. One study documented a decrease in performance, and two studies reported no learning improvement Conflicting evidence was reported regarding which feedback frequency, timing, and duration was most appropriate. Furthermore, the inconsistency in methodological designs (control group types; timing of retention-tests; lack of retention tests) limited the comparisons that could be made between studies. Eighteen studies reported a high risk of bias, with the remaining six presenting some concerns.ConclusionAlthough studies have shown positive effects of AF on the performance and learning of gross motor and sport-specific skills, the majority are at a high risk of bias. Additionally, studies lacked standardisation in methodology, and results surrounding features of AF interventions were conflicting. Despite the conceptually sound rationale, further research is required to provide stronger evidence and a more robust understanding to better inform practitioners on how AF truly impacts the performance and learning of gross motor and sport-specific skills.RegistrationThis systematic review was registered on the Open Science Framework (https://osf.io/mrxzg) (10.17605/OSF.IO/MRXZG)     

Opportunities for learning and social interaction in infant sitting: Effects of sitting support,sitting skill,and gross motor delay

The development of independent sitting changes everyday opportunities for learning and has cascading effects on cognitive and language development. Prior to independent sitting, infants experience the sitting position with physical support from caregivers. Why does supported sitting not provide the same input for learning that is experienced in independent sitting? This question is especially relevant for infants with gross motor delay, who require support in sitting for many months after typically developing infants sit independently. We observed infants with typical development (n = 34, ages 4–7 months) and infants with gross motor delay (n = 128, ages 7–16 months) in early stages of sitting development, and their caregivers, in a dyadic play observation. We predicted that infants who required caregiver support for sitting would spend more time facing away from the caregiver and less time contacting objects than infants who could sit independently. We also predicted that caregivers of supported sitters would spend less time contacting objects because their hands would be full supporting their infants. Our first two hypotheses were confirmed; however, caregivers spent surprisingly little time using both hands to provide support, and caregivers of supported sitters spent more time contacting objects than caregivers of independent sitters. Similar patterns were seen in the group of typically developing infants and the infants with motor delay. Our findings suggest that independent sitting and supported sitting provide qualitatively distinct experiences with different implications for social interaction and learning opportunities.

Highlights

• During seated free play, supported sitters spent more time facing away from their caregivers and less time handling objects than independent sitters.
• Caregivers who spent more time supporting infants with both hands spent less time handling objects; however, caregivers mostly supported infants with one or no hands.
• A continuous measure of sitting skill did not uniquely contribute to these behaviors beyond the effect of binary sitting support (supported vs. independent sitter).
• The pattern of results was similar for typically developing infants and infants with gross motor delay, despite differences in age.

     

Postural Stability in Children with High Sacral Level Spina Bifida: Deviations from a Control Group

Abstract

Objective: To assess static and dynamic postural stability changes in children with high sacral level spina bifida.

Methods: Thirty-five children with high sacral level spina bifida and 35 age-matched healthy controls were enrolled. Their lower extremity muscle strengths and static and dynamic postural stability parameters were measured with the use of a dynamometer and the NeuroCom Balance Master^® device, respectively. Functional gait and balance were evaluated using the five times sit-to-stand test (5STS) and the 6-minute walk test (6MWT). Spinal, hip, and ankle deformities of the patient group were measured by radiologic evaluation.

Results: In comparison with controls, patients were found to have lower ankle dorsiflexion and plantar-flexion strength, increased 5STS duration, and decreased 6MWT distance while both static and dynamic postural stability parameters were significantly different. Bilateral ankle muscle strengths were found to be negatively correlated with postural stability parameters. The presence of hydrocephalus or meningomyelocele in the patient group was found to have negative effects on static postural stability.

Conclusion: Static and dynamic postural stability is affected even in children with high sacral level spina bifida who are expected to have best condition in this patient population. The ankle muscle strength is the main factor influencing these changes.     

Motor learning of cue-dependent pull-force changes during an isometric precision grip task

The “raspberry task” represents a precision grip task that requires continuous adjustment of grip and pull forces. During this task subjects grip a specialized grip rod and have to increase the pull force linearly while the rod is locked. The aim of this study was to determine whether an associated, initially neutral cue is able to evoke pull-force changes in the raspberry task. A standard delay paradigm was used to study cued pull-force changes during an ongoing movement resulting in unloading. Pull force and EMG activity of hand and arm muscles were recorded from 13 healthy, young subjects. The cue was associated with a complex change in motor behavior.In this task, cued force changes take place more rapidly than in protective reflex systems (in median after the second presentation of the cueing stimulus). A cued force change was detectable in two-thirds of paired trials. Although the force change is produced by a decrease of the EMG activity in several grip- and pull-force-producing muscles, the most significant effect in the majority of the subjects was an increase of the activity of the flexor carpi ulnaris muscle which antagonises corresponding pull-force-producing muscles. Cued force changes require adequately and precisely controlled activation of the muscle groups involved in the movement.     

The relation between cognitive and motor performance and their relevance for children’s transition to school: A latent variable approach

Both theoretically and empirically there is a continuous interest in understanding the specific relation between cognitive and motor development in childhood. In the present longitudinal study including three measurement points, this relation was targeted. At the beginning of the study, the participating children were 5–6-year-olds. By assessing participants’ fine motor skills, their executive functioning, and their non-verbal intelligence, their cross-sectional and cross-lagged interrelations were examined. Additionally, performance in these three areas was used to predict early school achievement (in terms of mathematics, reading, and spelling) at the end of participants’ first grade. Correlational analyses and structural equation modeling revealed that fine motor skills, non-verbal intelligence and executive functioning were significantly interrelated. Both fine motor skills and intelligence had significant links to later school achievement. However, when executive functioning was additionally included into the prediction of early academic achievement, fine motor skills and non-verbal intelligence were no longer significantly associated with later school performance suggesting that executive functioning plays an important role for the motor-cognitive performance link.     

Cognitive and motor deficits in older adults with HIV infection: Comparison with normal ageing and Parkinson’s disease

Despite the life-extending success of antiretroviral pharmacotherapy in HIV infection (HIV), the prevalence of mild cognitive impairment in HIV remains high. Near-normal life expectancy invokes an emerging role for age–infection interaction and a potential synergy between immunosenescence and HIV-related health factors, increasing risk of cognitive and motor impairment associated with degradation in corticostriatal circuits. These neural systems are also compromised in Parkinson’s disease (PD), which could help model the cognitive deficit pattern in HIV. This cross-sectional study examined three groups, age 45–79 years: 42 HIV, 41 PD, and 37 control (CTRL) participants, tested at Stanford University Medical School and SRI International. Neuropsychological tests assessed executive function (EF), information processing speed (IPS), episodic memory (MEM), visuospatial processing (VSP), and upper motor (MOT) speed and dexterity. The HIV and PD deficit profiles were similar for EF, MEM, and VSP. Although only the PD group was impaired on MOT compared with CTRL, MOT scores were related to cognitive scores in HIV but not PD. Performance was not related to depressive symptoms, socioeconomic status, or CD4⁺ T-cell counts. The overlap of HIV-PD cognitive deficits implicates frontostriatal disruption in both conditions. The motor-cognitive score relation in HIV provides further support for the hypothesis that these processes share similar underlying mechanisms in HIV infection possibly expressed with or exacerbated by ageing.     

The Effects of Attentional Focus Instructions and Task Difficulty in a Paced Fine Motor Skill

Abstract

An external focus of attention is considered superior to an internal focus for learning and performance. However, findings specific to changing the task difficulty are inconsistent. The present study used a reciprocal aiming task to determine the effects of attentional focus on motor performance using speed-accuracy paradigm. We constrained timing to examine how internal and external focus of attention influenced accuracy when task difficulty changes. The results indicated greater accuracy on the right target and greater consistency on both targets for the external focus condition, regardless of task difficulty. Our results uniquely demonstrated how instruction modified a speed-accuracy task.