Associations Between Lower Limb Isometric Torque, Isokinetic Torque, and Explosive Force With Phases of Reactive Stepping in Young, Healthy Adults.

This study aimed to determine the relationship between lower limb muscle strength and explosive force with force plate-derived timing measures of reactive stepping. Nineteen young, healthy adults responded to 6 perturbations using an anterior lean-and-release system. Foot-off, swing, and restabilization times were estimated from force plates. Peak isokinetic torque, isometric torque, and explosive force of the knee extensors/flexors and plantar/dorsiflexors were measured using isokinetic dynamometry. Correlations were run based on a priori hypotheses and corrected for the number of comparisons (Bonferroni) for each variable. Knee extensor explosive force was negatively correlated with swing time (r = -.582, P = .009). Knee flexor peak isometric torque also showed a negative association with restabilization time (r = -.459, P = .048); however, this was not statistically significant after correcting for multiple comparisons. There was no significant relationship between foot-off time and knee or plantar flexor explosive force (P > .025). These findings suggest that there may be utility to identifying specific aspects of reactive step timing when studying the relationship between muscle strength and reactive balance control. Exercise training aimed at improving falls risk should consider targeting specific aspects of muscle strength depending on specific deficits in reactive stepping.

Quantifying the amount of physical rehabilitation received by individuals living with neurological conditions in the community: a scoping review.

BACKGROUND: Physical rehabilitation is often prescribed immediately following a neurological event or a neurological diagnosis. However, many individuals require physical rehabilitation after hospital discharge. The purpose of this scoping review was to determine the amount of physical rehabilitation that individuals living in the community with neurological conditions receive to understand current global practices and assess gaps in research and service use. METHODS: This scoping review included observational studies that 1) involved adults living with a neurological condition, and 2) quantified the amount of rehabilitation being received in the community or outpatient hospital setting. Only literature published in English was considered. MEDLINE, EMBASE, AMED, CINAHL, Cochrane Library, and PEDro databases were searched from inception. Two independent reviewers screened titles and abstracts, followed by full texts, and data extraction. Mean annual hours of rehabilitation was estimated based on the amount of rehabilitation reported in the included studies. RESULTS: Overall, 18 studies were included after screen 14,698 articles. The estimated mean annual hours of rehabilitation varied greatly (4.9 to 155.1 h), with individuals with spinal cord injury and stroke receiving the greatest number of hours. Participants typically received more physical therapy than occupational therapy (difference range: 1 to 22 h/year). Lastly, only one study included individuals with progressive neurological conditions, highlighting a research gap. DISCUSSION: The amount of rehabilitation received by individuals with neurological conditions living in the community varies greatly. With such a wide range of time spent in rehabilitation, it is likely that the amount of rehabilitation being received by most individuals in the community is insufficient to improve function and quality of life. Future work should identify the barriers to accessing rehabilitation resources in the community and how much rehabilitation is needed to observe functional improvements.

Study Paradigms and Principles Investigated in Motor Learning Research After Stroke: A Scoping Review.

OBJECTIVES: To (1) characterize study paradigms used to investigate motor learning (ML) poststroke and (2) summarize the effects of different ML principles in promoting skill acquisition and retention. Our secondary objective is to evaluate the clinical utility of ML principles on stroke rehabilitation. DATA SOURCES: Medline, Excerpta Medica Database, Allied and Complementary Medicine, Cumulative Index to Nursing and Allied Health Literature, and Cochrane Central Register of Controlled Trials were searched from inception on October 24, 2018 and repeated on June 23, 2020. Scopus was searched on January 24, 2019 and July 22, 2020 to identify additional studies. STUDY SELECTION: Our search included keywords and concepts to represent stroke and "motor learning. An iterative process was used to generate study selection criteria. Three authors independently completed title, abstract, and full-text screening. DATA EXTRACTION: Three reviewers independently completed data extraction. DATA SYNTHESIS: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension guidelines for scoping reviews were used to guide our synthesis. Thirty-nine studies were included. Study designs were heterogeneous, including variability in tasks practiced, acquisition parameters, and retention intervals. ML principles investigated included practice complexity, feedback, motor imagery, mental practice, action observation, implicit and explicit information, aerobic exercise, and neurostimulation. An additional 2 patient-related factors that influence ML were included: stroke characteristics and sleep. Practice complexity, feedback, and mental practice/action observation most consistently promoted ML, while provision of explicit information and more severe strokes were detrimental to ML. Other factors (ie, sleep, practice structure, aerobic exercise, neurostimulation) had a less clear influence on learning. CONCLUSIONS: Improved consistency of reporting in ML studies is needed to improve study comparability and facilitate meta-analyses to better understand the influence of ML principles on learning poststroke. Knowledge of ML principles and patient-related factors that influence ML, with clinical judgment can guide neurologic rehabilitation delivery to improve patient motor outcomes.

Test-retest reliability of force plate-derived measures of reactive stepping.

Characterizing reactive stepping is important to describe the response's effectiveness. Timing of reactive step initiation, execution, and termination have been frequently reported to characterize reactive balance control. However, the test-retest reliabilities of these measures are unknown. Accordingly, the purpose of this study was to determine the between- and within-session test-retest reliabilities of various force plate-derived measures of reactive stepping. Nineteen young, healthy adults responded to 6 small (~8-10% of body weight) and 6 large perturbations (~13-15% of body weight) using an anterior lean-and-release system. Tests were conducted during two visits separated by at least two days. Participants were instructed to recover balance in as few steps as possible. Step onset, foot-off, swing, and restabilization times were extracted from force plates. Relative test-retest reliability was determined through intraclass correlation coefficients (ICCs) and 95% confidence intervals (CIs). Absolute test-retest reliability was assessed using the standard error of the measurement (SEM). Foot-off and swing times had the highest between- and within-session test-retest reliabilities regardless of perturbation size (between-session ICC = 0.898-0.942; within-session ICC = 0.455-0.753). Conversely, step onset and restabilization times had lower ICCs and wider CIs (between-session ICC = 0.495-0.825; within-session ICC = -0.040-0.174). Between-session test-retest reliability was higher (ICC = 0.495-0.942) for all measures than within-session test-retest reliability (ICC = -0.040-0.753). Time to restabilization had the highest SEM, indicating the worst absolute reliability of the measures. These findings suggest multiple baseline sessions are needed for measuring restabilization and step onset times. The minimal detectable changes reported provide an index for measuring meaningful change due to an intervention.

Intensive Care Unit-Acquired Weakness: Not just Another Muscle Atrophying Condition.

Intensive care unit-acquired weakness (ICUAW) occurs in critically ill patients stemming from the critical illness itself, and results in sustained disability long after the ICU stay. Weakness can be attributed to muscle wasting, impaired contractility, neuropathy, and major pathways associated with muscle protein degradation such as the ubiquitin proteasome system and dysregulated autophagy. Furthermore, it is characterized by the preferential loss of myosin, a distinct feature of the condition. While many risk factors for ICUAW have been identified, effective interventions to offset these changes remain elusive. In addition, our understanding of the mechanisms underlying the long-term, sustained weakness observed in a subset of patients after discharge is minimal. Herein, we discuss the various proposed pathways involved in the pathophysiology of ICUAW, with a focus on the mechanisms underpinning skeletal muscle wasting and impaired contractility, and the animal models used to study them. Furthermore, we will explore the contributions of inflammation, steroid use, and paralysis to the development of ICUAW and how it pertains to those with the corona virus disease of 2019 (COVID-19). We then elaborate on interventions tested as a means to offset these decrements in muscle function that occur as a result of critical illness, and we propose new strategies to explore the molecular mechanisms of ICUAW, including serum-related biomarkers and 3D human skeletal muscle culture models.

The effect of bed rest on balance control in healthy adults: A systematic scoping review.

The objective of this study was to determine the effect of bed rest on balance control and the mechanisms responsible for these changes. Searches were conducted in six databases. Studies had to be conducted on healthy adults who were subjected to bed rest (≥5 days), with balance control measures obtained before and after bed rest in order to be included. Risk of bias was assessed using the NIH Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. After screening 9,785 articles, 18 were included for qualitative synthesis. Fifteen studies found decrements in at least one balance control measure following bed rest, either compared to baseline or controls, with eight studies observing impairments in >50% of their balance control measures. Of the 14 studies that included an intervention, four (mechanical stimuli, lower-body negative pressure, and training targeting strength, balance and/or aerobic capacity) successfully offset the majority of balance control deficits and targeted the musculoskeletal and cardiovascular systems. The findings of this review support bed rest negatively affecting balance control in healthy individuals. In clinical populations, these deficits may be further accentuated due to various comorbidities that impact balance control systems. PROSPERO Registration: CRD42018098887.

A scoping review to characterize bridging tasks in the literature on aging with disability.

BACKGROUND: Bridging involves improving knowledge sharing and collaboration across different fields, such as aging and disability. The objectives of this review were to describe: 1) the contexts where bridging has occurred in relation to delivery of health services for adults aging with neurological or developmental conditions; and 2) characterize and map bridging tasks, stakeholders involved, and outcomes discussed in peer-reviewed literature. METHODS: Seven databases were searched around the core concepts of "bridging," "aging," and "disability." In total, 10,819 articles were screened with 49 meeting the inclusion criteria of discussing aging with developmental or neurological disability, explicitly describing bridging tasks, published in English and a peer-reviewed publication. Bibliographic information, sample characteristics, and data on bridging was extracted and included in the qualitative synthesis. RESULTS: Intellectual and/or Developmental disabilities were the most studied population (76% of articles), and most articles were published in the United States (57%). Twenty-two bridging tasks were identified, and categorized into three domains: health and social service delivery (e.g., care coordination tasks), policy (e.g., policy change), and research and training (e.g., mentoring). Stakeholders involved ranged from health care professionals to policy makers and organizations in aging and disability services. CONCLUSIONS: The resulting matrix will assist in the specification of bridging in research and practice. Future work should evaluate specific models of bridging and their effects on health service delivery.

Using Motor Imagery Training to Increase Quadriceps Strength: A Pilot Study.

BACKGROUND: Motor imagery training implements neural adaptation theory to improve muscle strength without physically performing muscle contractions. To date, motor imagery training research regarding the efficacy of improving torque of the quadriceps over a brief training period is limited. OBJECTIVE: To determine the impact of a 3-week motor imagery training on peak torque during knee extension. METHOD: Ten young, healthy volunteers were randomly assigned to 1 of 3 groups over a 3-week period: strength training, motor imagery training and control. RESULTS: Following training, an increase in peak torque was observed in all strength training participants (mean change of 38 ± 15%) and in 2 members of the motor imagery training group (45 ± 10%). CONCLUSION: Brief periods of motor imagery training may have the potential to improve quadriceps strength; however, more research is needed with larger populations to test this hypothesis.

Single pulse TMS during preparation for lower limb movement: Effect of task predictability on corticospinal excitability.

Motor preparation involves inhibitory and excitatory processes that influence the scaling and efficiency of movement. Understanding the modulation of these processes when predictability is altered can provide insight as to how individuals prepare for temporally-urgent scenarios where the lower limbs are engaged. This study aimed to determine the influence of task predictability on preparatory corticospinal excitability during a 3 s foreperiod. It was hypothesized that during preparation for an unpredictable choice (go/no-go) reaction time task, corticospinal excitability would be facilitated compared to the responses measured for the predictable (simple) reaction time task. Twenty-eight healthy young adults participated in two reaction time tasks (predictable and unpredictable) using a go/no-go paradigm. During the foreperiod, transcranial magnetic stimulation was applied over the left primary motor cortex to elicit a motor-evoked potential in the right tibialis anterior muscle. Task predictability had a significant effect on corticospinal excitability when controlling for task order [F(1,25) = 7.124, p = 0.013], with the unpredictable task augmenting corticospinal excitability to a greater extent than the predictable task. When the predictable condition was performed first, MEP amplitude was 109.2 ±â€¯14.3% of baseline for the predictable task and 124.0 ±â€¯15.4% for the unpredictable task. In contrast, when the unpredictable condition was performed first, MEP amplitude was 119.5 ±â€¯14.4% for the unpredictable task and 126.6 ±â€¯10.1% for the predictable task. These results suggest that unpredictability may require individuals to have a heightened attention to incoming stimuli, thereby increasing corticospinal excitability, which can be maintained in subsequent predictable scenarios.