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Saint Paul, MN, United States

van der Krogt M.M.,VU University Amsterdam | van der Krogt M.M.,University of Twente | Delp S.L.,Stanford University | Schwartz M.H.,Gillette Childrens Specialty Healthcare | Schwartz M.H.,University of Minnesota
Gait and Posture | Year: 2012

Humans have a remarkable capacity to perform complex movements requiring agility, timing, and strength. Disuse, aging, and disease can lead to a loss of muscle strength, which frequently limits the performance of motor tasks. It is unknown, however, how much weakness can be tolerated before normal daily activities become impaired. This study examines the extent to which lower limb muscles can be weakened before normal walking is affected. We developed muscle-driven simulations of normal walking and then progressively weakened all major muscle groups, one at the time and simultaneously, to evaluate how much weakness could be tolerated before execution of normal gait became impossible. We further examined the compensations that arose as a result of weakening muscles. Our simulations revealed that normal walking is remarkably robust to weakness of some muscles but sensitive to weakness of others. Gait appears most robust to weakness of hip and knee extensors, which can tolerate weakness well and without a substantial increase in muscle stress. In contrast, gait is most sensitive to weakness of plantarflexors, hip abductors, and hip flexors. Weakness of individual muscles results in increased activation of the weak muscle, and in compensatory activation of other muscles. These compensations are generally inefficient, and generate unbalanced joint moments that require compensatory activation in yet other muscles. As a result, total muscle activation increases with weakness as does the cost of walking. By clarifying which muscles are critical to maintaining normal gait, our results provide important insights for developing therapies to prevent or improve gait pathology. © 2012 Elsevier B.V. Source


Barney C.C.,Gillette Childrens Specialty Healthcare
Developmental Medicine and Child Neurology | Year: 2015

This commentary is on the original article by Valkenburg et al. on pages 1049-1055 of this issue. Developmental Medicine and Child Neurology. © 2015 Mac Keith Press. Source


Drummond A.,Gillette Childrens Specialty Healthcare | Looman W.S.,University of Minnesota | Phillips A.,Minnesota Gastroenterology
Journal of Pediatric Health Care | Year: 2012

Introduction: Having a health care home has been shown to be associated with positive health outcomes for children with special health care needs (CSHCN), but its relationship to parental coping has not been established. The purpose of this study was to explore the health care home as a process of care related to parental coping with day-to-day demands of raising a CSHCN. Method: Data are from a sample of 18,352 CSHCN in the 2007 National Survey of Children's Health. Using the Behavioral Model of Health Services Use as a framework, this secondary analysis explored relationships between child and household factors and parental coping among CSHCN with and without a health care home. Results: CSHCN in a health care home were more likely to have parents who were coping well. Parents who received sufficient care coordination were more satisfied with provider communication, and those who reported that care was family-centered reported better coping. Discussion: Results suggest that the health care home represents a process of care that may help families manage the daily demands of caring for CSHCN through family-centered care, provider-to-provider communication, and provision of care coordination. © 2012 National Association of Pediatric Nurse Practitioners. Source


Gutknecht S.M.,Gillette Childrens Specialty Healthcare | Schwartz M.H.,University of Minnesota | Schwartz M.H.,Center for Gait and Motion Analysis | Munger M.E.,Center for Gait and Motion Analysis
Developmental Medicine and Child Neurology | Year: 2015

Aim: The aim of this study was to retrospectively analyze changes in age- and sex-adjusted body mass index (BMI) in ambulatory children with cerebral palsy (CP) who underwent selective dorsal rhizotomy (SDR). Method: Raw BMI, age- and sex-adjusted BMI z-scores, weight classification status, energy expenditure, and ambulation function were calculated before and after SDR at multiple post-SDR time points: 6 to <24 months, 24 to <48 months, 48 to <72, and 72 to <96 months. Linear mixed models were used to analyze changes in raw BMI, BMI z-scores, energy expenditure, and ambulation function. Results: Pre- and post-surgical data were available for 363 children diagnosed with CP who underwent SDR (219 males, 144 females; mean age 6y [SD 2y 1mo]; mean BMI z-score 0.09 [SD 1.21]). Data from additional post-surgical time points were collected on subsamples. Although raw BMI significantly increased (p<0.01), these increases were consistent with anticipated growth. BMI z-scores did not significantly change over the 10-year study period. Interpretation: Concerns of unhealthy weight gain following SDR are not supported by this study. Further work examining possible risk factors for BMI increase following SDR, as well as examining disparities in existing criteria for patient selection, is merited. © 2015 Mac Keith Press. Source


Novotny S.A.,Gillette Childrens Specialty Healthcare | Warren G.L.,Georgia State University | Hamrick M.W.,Georgia Regents University
Physiology | Year: 2015

Aging-induced declines in muscle size and quality are thought to contribute to catabolic alterations in bone, but changes in bone with age also profoundly alter its response to muscle-derived stimuli. This review provides an overview of some of the alterations that occur in muscle and bone with aging, and discusses the cellular and molecular mechanisms that may impact these ageassociated changes. © 2015 Int. Union Physiol. Sci./Am. Physiol. Soc. Source

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