No abstract

Non-technical summary Muscle spasticity, due to an upper motoneuron lesion, often leads to muscle contractures that limit range of motion and cause increased muscle stiffness. However, the elements responsible for this muscle adaption are unknown. Here we show that muscle tissue is stiffer in contracture compared to age-matched children, implicating the extracellular matrix (ECM). However, titin, the major load-bearing protein within muscle fibres, is not altered in contracture, and individual fibre stiffness is unaltered. Increased ECM stiffness is even more functionally significant given our finding of long in vivo sarcomeres which leads to much larger in vivo forces in muscle contracture. These results may lead to novel therapeutics for treating spastic muscle contracture.Abstract Cerebral palsy (CP) results from an upper motoneuron (UMN) lesion in the developing brain. Secondary to the UMN lesion, which causes spasticity, is a pathological response by musclenamely, contracture. However, the elements within muscle that increase passive mechanical stiffness, and therefore result in contracture, are unknown. Using hamstring muscle biopsies from pediatric patients with CP (n = 33) and control (n = 19) patients we investigated passive mechanical properties at the protein, cellular, tissue and architectural levels to identify the elements responsible for contracture. Titin isoform, the major load-bearing protein within muscle cells, was unaltered in CP. Correspondingly, the passive mechanics of individual muscle fibres were not altered. However, CP muscle bundles, which include fibres in their constituent ECM, were stiffer than control bundles. This corresponded to an increase in collagen content of CP muscles measured by hydroxyproline assay and observed using immunohistochemistry. In vivo sarcomere length of CP muscle measured during surgery was significantly longer than that predicted for control muscle. The combination of increased tissue stiffness and increased sarcomere length interact to increase stiffness greatly of the contracture tissue in vivo. These findings provide evidence that contracture formation is not the result of stiffening at the cellular level, but stiffening of the ECM with increased collagen and an increase of in vivo sarcomere length leading to higher passive stresses.

The biomechanical findings of this study offer scientific feedback for developing methods used to minimize the effects of valgus load on pitching-related elbow injuries.

High rotational torques during baseball pitching are believed to be linked to most overuse injuries at the shoulder. This study investigated the effects of trunk rotation on shoulder rotational torques during pitching. A total of 38 pitchers from the professional, college, high school, and youth ranks were recruited for motion analysis. Professional pitchers demonstrated the least amount of rotational torque (p= .001) among skeletally mature players, while exhibiting the ability to rotate their trunks significantly later in the pitching cycle, as compared to other groups (p= .01). It was concluded that the timing of their rotation was optimized as to allow the throwing shoulder to move with decreased joint loading by conserving the momentum generated by the trunk. These results suggest that a specific pattern in throwing can be utilized to increase the efficiency of the pitch, which would allow a player to improve performance with decreased risk of overuse injury.

No abstract

Background: Cerebral palsy (CP) is an upper motor neuron disease that results in a progressive movement disorder. Secondary to the neurological insult, muscles from CP patients often become spastic. Spastic muscle is characterized by an increased resistance to stretch, but often develops the further complication of contracture which represents a prominent disability in children with CP. This study's purpose is to characterize alterations of spastic muscle on the transcriptional level. Increased knowledge of spastic muscle may lead to novel therapies to improve the quality of life for children with CP.

No abstract

The aim of the study was to determine whether pediatric patients with cerebral palsy (CP; 24.3% hemiplegic, 30.4% diplegic, 38.5% quadriplegic) can self-report their health-related quality of life (HRQOL) with the Pediatric Quality of Life Inventory Version 4.0 (PedsQL 4.0) Generic Core Scales. The PedsQL was administered to 148 families (84 males, 64 females; mean 10y, SD 3y 9mo, range 5 to 18y) recruited from a children's hospital clinic and state medical therapy clinics. Sixty-nine children (47%) were able to self-report. Children with CP self-reported a significantly lower HRQOL (mean 65.9) than healthy children (mean 83.8). Children with CP self-reported a similar HRQOL to pediatric cancer patients receiving treatment (mean 68.9). Children diagnosed with quadriplegia (mean 49.4) self-reported more impaired HRQOL than children with diplegia (mean 69.1) and hemiplegia (mean 72.4). Parent-child concordance was lowest for emotional functioning. Providers and parents should obtain the children's HRQOL perceptions whenever possible.