Vastus lateralis fascicle length changes during stair ascent and descent.

STUDY DESIGN: Experimental descriptive laboratory study. OBJECTIVES: To describe the change in fascicle length of the human vastus lateralis (VL) muscle during the stance phase of stair ascent and descent. BACKGROUND: Muscle fascicle length changes during lower limb functional activities, such as walking and jumping, do not always coincide with joint angle changes. METHODS AND MEASURES: Thirty-three healthy, college-age women walked up and down 4 standard steps. VL fascicle length and pennation angle were measured using real-time ultrasonography. Knee angle was monitored using an electrical goniometer. Foot switches indicated foot contact and release. VL muscle activity was monitored using surface electrodes. The VL muscle-tendon complex and tendon length were calculated based on published models. RESULTS: During initial weight acceptance in stair ascent, the knee joint extended only 3 degrees , VL muscle activity increased to a maximum, VL fascicles shortened, and the tendon lengthened. As the knee extended to ascend the step, the fascicles and tendon shortened throughout the movement. During weight acceptance in stair descent, VL muscle activity increased, VL fascicle length did not change significantly, but the tendon lengthened as 10 degrees of knee flexion occurred. As the knee flexed to complete descent, VL muscle activity peaked, and VL fascicles and tendon lengthened. CONCLUSION: VL fascicles shorten and lengthen as expected during the respective knee extension and knee flexion phases of stair ascent and descent. However, during initial weight acceptance in both stair ascent and descent, the fascicle length change did not coincide with the knee joint kinematics.

Emotional, developmental, and behavioral health of American children and their families: a report from the 2003 National Survey of Children's Health.

BACKGROUND: Recent children's health surveys have documented a high prevalence of emotional, developmental, and behavioral problems among children. Data from the 2003 National Survey of Children's Health provide new insights into these problems and their association with family function and community participation. These issues have become a current focus of the World Health Organization. METHODS: Answers to questions of interest from the 2003 National Survey of Children's Health were reported using estimates and SEs of rates. Statistical comparisons of rates with chi2 tests at the 0.05 level were made when relevant. RESULTS: The most commonly diagnosed problems among children 6-17 years of age were learning disabilities (11.5%), attention-deficit/hyperactivity disorder (8.8%), and behavioral problems (6.3%); among preschoolers, speech problems (5.8%) and developmental delay (3.2%) were most common. One in 200 children was diagnosed with autism. In contrast, rates of parental concerns about emotional, developmental, or behavioral problems were much higher; for example, 41% of parents had concerns about learning difficulties and 36% about depression or anxiety. Children with developmental problems had lower self-esteem, more depression and anxiety, more problems with learning, missed more school, and were less involved in sports and other community activities. Their families experienced more difficulty in the areas of childcare, employment, parent-child relationships, and caregiver burden. CONCLUSIONS: The most recent National Survey of Children's Health mirrored results of previous surveys regarding rates of diagnosed emotional, developmental, and behavioral problems, including an escalating diagnosis of autism among children. Reported rates of parental concerns about these problems were much higher, suggesting possible underdiagnosis of children's problems. Children with chronic problems had diminished family functioning, more school absences, and less participation in community activities compared with other children. Their parents experienced more difficulty with childcare, employment, and parenting skills. A change in treatment emphasis is needed, away from an exclusive focus on a child's developmental and behavioral problems to one that addresses the impacts of these problems on the family and community participation. A new approach to the way these issues are addressed and managed has the potential to enhance the quality of life for a child, as well as the parents, and to produce more meaningful and tangible solutions to these complex and increasingly evident problems.