Quantification of muscle fatigue in cerebal palsy and its relationship to impairments and function

Three experiments were designed to explore the measurement of muscle fatigue in people with cerebral palsy (CP). The four aims were to 1) develop a feasible and reliable isokinetic protocol to assess muscle fatigue of the knee flexors and extensors in this population, 2) determine if muscle fatigue of the knee flexors and extensors in people with CP differs from subjects without a motor disorder, 3) determine whether muscle fatigue is related to functional measures of activity and participation, and 4) investigate possible contributing factors of muscle fatigue. Results show that muscle fatigue can be reliably assessed through an isokinetic protocol consisting of 35 consecutive knee extension and flexion repetitions at 60 degrees/second by calculation of a fatigue index (FI) and the slope of the decline in peak torque. When compared to a control group of age-matched peers without motor disorder, the knee flexors and extensors in subjects with CP were observed to be less fatigable. Furthermore, muscle fatigue of the knee extensors and flexors in the group with CP was positively correlated with transfers and basic mobility. Muscle fatigue of the knee extensors was also positively correlated with overall global functioning, participation in sports and physical function, and fast walking velocity. Lower Gross Motor Function Classification System Levels (GMFCS) (i.e. less involved subjects) were also associated with higher levels of muscle fatigability. Strength was directly related to muscle fatigability, where weaker subjects had lower levels of fatigue, regardless of muscle. Cocontraction and quadriceps stiffness, on the other hand, were inversely related to muscle fatigability. The strongest predictors of hamstring fatigability were hamstrings strength and quadriceps stiffness, whereas the strongest predictor of quadriceps fatigability was hamstring cocontraction. The presence of spasticity, regardless of muscle group, was associated with lower fatigability compared to control subjects. In summary, the results indicate that the knee flexors and extensors of people with CP are less fatigable than age-matched peers without motor disability. In addition, lower levels of muscle fatigability are associated with lower levels of function and participation. Furthermore, weakness, spasticity, stiffness, and cocontraction are possible contributing factors to the observed fatigue resistance

Reliability and Validity of Three Clinical Methods to Measure Lower Extremity Muscle Power

Background: Lower extremity muscle power is critical for daily activities and athletic performance in clinical populations. Objective: The purpose of this study was to determine the reliability and validity of 3 clinically feasible methods to measure lower extremity muscle power during a leg press. Methods: Ten of 26 subjects performed 2 sessions of 5 submaximal leg presses separated by 3-7 days in this repeated-measures cross-sectional design; the remaining performed 1 test session. Power was calculated independently for each method [simple video, linear position transducer, and accelerometer] and compared to the reference force plate. Test-retest reliability was evaluated using intraclass correlation coefficients (ICC). Pearson’s correlation coefficient (r), Bland-Altman plots with 95% limits of agreement (LOA), and mean bias percentages (%) were used to determine relative and absolute validity. Results: Power measures were reliable for all methods (ICC=.97-.99). All were highly correlated with the force plate (r=.96-.98). Mean bias was -0.8% (LOA: -16.57% to 14.98%) (video), -13.21% (LOA: -23.81% to -2.61%) (position transducer) compared to the force plate. Proportional bias was observed for accelerometry. Conclusion: All methods were reliable and highly correlated with the force plate. Only the video and position transducer demonstrated absolute validity. The position transducer was the most feasible method because of its simplicity and accuracy in measuring power

Urban Versus Rural Differences in Insurance Coverage and Impact on Employment Among Families Caring for a Child With Cerebral Palsy

Background: The purpose of this study was to examine urban vs. rural differences on the relationship between family contextual variables and adequacy of insurance coverage and impact on employment for among families with a child with Cerebral Palsy from a nationally representative sample. Methods: A retrospective, observational study was carried out using data from the National Survey of Children with Special Healthcare Needs. Results: A total of 744 participants reported as having a child with a diagnosis of Cerebral Palsy and were included in the sample. Logistic regression analyses, adjusting for urban and rural setting revealed different predictors of adequacy of insurance coverage and impact on employment. Among urban respondents, three variables with odds ratios ranging from 1.33 to 1.58 served as protective factors, increasing the likelihood of adequate insurance coverage. Four variables with odds ratios ranging from 1.41 to 1.79 decreased the likelihood of negatively impacting employment. Among rural families, there was only one significant protective factor for adequacy of insurance coverage (odds ratio 1.80) and one for decreasing the chances of impact on employment (odds ratio 2.53). Conclusion: Families in rural areas caring for a child with CP have few protective factors for adequate insurance coverage and impact on familial employment

Lifelong Fitness in Ambulatory Children and Adolescents with Cerebral Palsy I: Key Ingredients for Bone and Muscle Health

Physical activity of a sufficient amount and intensity is essential to health and the prevention of a sedentary lifestyle in all children as they transition into adolescence and adulthood. While fostering a fit lifestyle in all children can be challenging, it may be even more so for those with cerebral palsy (CP). Evidence suggests that bone and muscle health can improve with targeted exercise programs for children with CP. Yet, it is not clear how musculoskeletal improvements are sustained into adulthood. In this perspective, we introduce key ingredients and guidelines to promote bone and muscle health in ambulatory children with CP (GMFCS I–III), which could lay the foundation for sustained fitness and musculoskeletal health as they transition from childhood to adolescence and adulthood. First, one must consider crucial characteristics of the skeletal and muscular systems as well as key factors to augment bone and muscle integrity. Second, to build a better foundation, we must consider critical time periods and essential ingredients for programming. Finally, to foster the sustainability of a fit lifestyle, we must encourage commitment and self-initiated action while ensuring the attainment of skill acquisition and function. Thus, the overall objective of this perspective paper is to guide exercise programming and community implementation to truly alter lifelong fitness in persons with CP

Identification of genetic variants associated with Huntington's disease progression: a genome-wide association study

Background Huntington's disease is caused by a CAG repeat expansion in the huntingtin gene, HTT. Age at onset has been used as a quantitative phenotype in genetic analysis looking for Huntington's disease modifiers, but is hard to define and not always available. Therefore, we aimed to generate a novel measure of disease progression and to identify genetic markers associated with this progression measure. Methods We generated a progression score on the basis of principal component analysis of prospectively acquired longitudinal changes in motor, cognitive, and imaging measures in the 218 indivduals in the TRACK-HD cohort of Huntington's disease gene mutation carriers (data collected 2008–11). We generated a parallel progression score using data from 1773 previously genotyped participants from the European Huntington's Disease Network REGISTRY study of Huntington's disease mutation carriers (data collected 2003–13). We did a genome-wide association analyses in terms of progression for 216 TRACK-HD participants and 1773 REGISTRY participants, then a meta-analysis of these results was undertaken. Findings Longitudinal motor, cognitive, and imaging scores were correlated with each other in TRACK-HD participants, justifying use of a single, cross-domain measure of disease progression in both studies. The TRACK-HD and REGISTRY progression measures were correlated with each other (r=0·674), and with age at onset (TRACK-HD, r=0·315; REGISTRY, r=0·234). The meta-analysis of progression in TRACK-HD and REGISTRY gave a genome-wide significant signal (p=1·12 × 10−10) on chromosome 5 spanning three genes: MSH3, DHFR, and MTRNR2L2. The genes in this locus were associated with progression in TRACK-HD (MSH3 p=2·94 × 10−8 DHFR p=8·37 × 10−7 MTRNR2L2 p=2·15 × 10−9) and to a lesser extent in REGISTRY (MSH3 p=9·36 × 10−4 DHFR p=8·45 × 10−4 MTRNR2L2 p=1·20 × 10−3). The lead single nucleotide polymorphism (SNP) in TRACK-HD (rs557874766) was genome-wide significant in the meta-analysis (p=1·58 × 10−8), and encodes an aminoacid change (Pro67Ala) in MSH3. In TRACK-HD, each copy of the minor allele at this SNP was associated with a 0·4 units per year (95% CI 0·16–0·66) reduction in the rate of change of the Unified Huntington's Disease Rating Scale (UHDRS) Total Motor Score, and a reduction of 0·12 units per year (95% CI 0·06–0·18) in the rate of change of UHDRS Total Functional Capacity score. These associations remained significant after adjusting for age of onset. Interpretation The multidomain progression measure in TRACK-HD was associated with a functional variant that was genome-wide significant in our meta-analysis. The association in only 216 participants implies that the progression measure is a sensitive reflection of disease burden, that the effect size at this locus is large, or both. Knockout of Msh3 reduces somatic expansion in Huntington's disease mouse models, suggesting this mechanism as an area for future therapeutic investigation

Urban vs. rural differences in insurance coverage and impact on employment among families caring for a child with cerebral palsy

Background: The purpose of this study was to examine urban vs. rural differences on the relationship between family contextual variables and adequacy of insurance coverage and impact on employment for among families with a child with Cerebral Palsy from a nationally representative sample. Methods: A retrospective, observational study was carried out using data from the National Survey of Children with Special Healthcare Needs. Results: A total of 744 participants reported as having a child with a diagnosis of Cerebral Palsy and were included in the sample. Logistic regression analyses, adjusting for urban and rural setting revealed different predictors of adequacy of insurance coverage and impact on employment. Among urban respondents, three variables with odds ratios ranging from 1.33 to 1.58 served as protective factors, increasing the likelihood of adequate insurance coverage. Four variables with odds ratios ranging from 1.41 to 1.79 decreased the likelihood of negatively impacting employment. Among rural families, there was only one significant protective factor for adequacy of insurance coverage (odds ratio 1.80) and one for decreasing the chances of impact on employment (odds ratio 2.53). Conclusion: Families in rural areas caring for a child with CP have few protective factors for adequate insurance coverage and impact on familial employment

Urban Versus Rural Differences in the Effects of Providing Care to Children With Cerebral Palsy on Family Member\u27s Employment

Background and Objective(s): Context (urban vs rural) can mediate the impact on the family among other childhood populations with special healthcare needs. To date, few studies have examined the role of context in caring for a child with CP; therefore, we analyzed data from the National Survey of Children with Special Health Care Needs (NS-CSHCN). Study Design: Cross-sectional. Study Participants & Setting: Participants were parents of children (\u3c 18y old) with CP. Children\u27s mean age of rural respondents was 10.17 (SD=4.69), while 73% were white, 13.5% Hispanic, 11% black, and 2.5% other (non-Hispanic). Among rural families, 33.05% were living in households with incomes below the Federal Poverty Level (FPL). For those respondents living in urban areas, children\u27s mean age was 9.74 (SD=4.50) and 63% were white, 13% Hispanic, 16% black, and 8% other (non-Hispanic). Overall 21.1% of urban families lived in households with incomes below the FPL. Materials/Methods: The NS-CSHCN was designed to examine state- and national-level estimates of CSHCN. A national random-digit-dial sample of US households were screened for children with special healthcare needs aged 0–17 years. Households reporting a CSHCN participated in an interview for one randomly selected child with a special healthcare need. Of 40 242 completed interviews from 2009 to 2011, 744 reported as having a child with a diagnosis of CP and were included in the sample. We performed logistic regression analyses, in the context of multiply imputed data to address missing data concerns, modeling the probability that family member\u27s employments were unaffected by the child\u27s health. Results: Our analysis indicated significant differences between families with children with CP living in an urban environment and those living in a rural setting concerning the impact that the child\u27s health had on family member\u27s work lives. There were six significant variables impacting the employment of family members for families living in an urban setting categories relating to missed school days, financial burden, and access to services (see Table 1). However, only a low financial burden and less time spent caring for the child were significant with regards to the impact on employment among rural families. Conclusions/Significance: Despite a higher percentage of families living in poverty, urban families had more protective factors to prevent the diagnosis of a child from impacting the employment of the family

Community-Based Upper Extremity Power Training for Youth with Cerebral Palsy: A Pilot Study

Aim: To examine the effects of an upper-extremity, community-based, and power-training intervention. Methods: Twelve participants with cerebral palsy (CP) [8 males, 4 females; mean age 14 years 6 months (SD 5 years 4 months), range 7–24] were randomly assigned to a rest-training (RT; n = 6) or training-rest (n = 6) group in this randomized, cross-over design. Training took place in participants’ home or school, three times per week for 6 weeks. We examined changes in upper extremity average power output (Pavg) in watts (W) and changes in function via the Pediatric Outcomes Data Collection Instrument (PODCI). Results: Each participant completed at least 15 of the 18 total training sessions (91.2% adherence). Pavg increased 92.2% on average among participants (p \u3c .05). There was a significant three-way interaction among treatment, sequence, and period with the data stratified by (Bimanual Fine Motor Function [BFMF]) level on the pain subscale of the PODCI (p = 0.0118). All participants decreased pain after training with the exception of individuals with lower functioning (BFMF II-V) in the RT group. Conclusion: A community-based upper extremity power-training intervention was feasible and effective at improving power among young people with CP and has the potential to improve pain