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Pforzheim, Germany

Anliker E.,ETH Zurich | Rawer R.,Novotec Medical GmbH | Boutellier U.,ETH Zurich | Boutellier U.,University of Zurich | And 3 more authors.
Medicine and Science in Sports and Exercise

Purpose: The purpose of the study was to assess maximum voluntary forefoot ground reaction force during multiple one-legged hopping (Fm1LH) and to determine the correlation between tibial volumetric bone mineral content (vBMC, a valid surrogate of bone strength) and Fm1LH. Methods: One hundred eighty-five females (8-82 yr old) and 138 males (8-71 yr old) performed multiple one-legged hopping to measure Fm1LH acting on the forefoot during landing. Peripheral quantitative computed tomography scans were obtained to assess vBMC at 4%, 14%, 38%, and 66% of tibia length and calf muscle cross-sectional area at the 66% site. Results: In all 323 participants, Fm1LH corresponded to 3-3.5 times body weight, and Fm1LH predicted vBMC14% by 84.0% (P < 0.001). vBMC14% was better correlated with Fm1LH than with the calf muscle cross-sectional area in both males (R = 0.841 vs R = 0.724) and females (R = 0.765 vs R = 0.597). Fm1LH and vBMC14% both increased during growth and afterward remained constant or decreased with age but never increased above the values reached at the end of puberty. Fm1LH decreased by 23.6% between 21-30 and 61-82 yr in females and by 14.0% between 31-40 and 51-71 yr in males. vBMC14% decreased by 13.7% in females between 21-30 and 61-82 yr but remained unchanged in adult males. Conclusions: Multiple one-legged hopping yields the highest (i.e., maximum) ground reaction force relative to other jumping maneuvers. Because bone strength is strongly governed by maximum muscle force, the concurrent assessment of peripheral quantitative computed tomography-derived bone strength and Fm1LH might represent a new approach for the operational evaluation of musculoskeletal health. © 2011 by the American College of Sports Medicine. Source

Anliker E.,ETH Zurich | Dick C.,ETH Zurich | Rawer R.,Novotec Medical GmbH | Toigo M.,ETH Zurich | And 2 more authors.
Journal of Musculoskeletal Neuronal Interactions

Objectives: To assess adaptations of the lower leg muscle-bone unit in 8- to 12-year-old children following a randomized controlled jumping exercise intervention for 9 months. Methods: Twelve boys and 10 girls (INT) performed a supervised jumping protocol during the first 10 min of their regularly scheduled physical education class twice a week, while 11 boys and 12 girls (CON) completed the regular curriculum. We assessed maximum voluntary ground reaction force during multiple one-legged hopping (Fm1LH), and tibial bone strength/geometry by peripheral quantitative computed tomography (pQCT) at the 4-, 14-, 38-and 66%-site pre, intermediate, and post intervention. Results: Whether increases in Fm1LH (+2.1% points, P= 0.752), nor changes in bone strength/geometry (+1 to +3% points, 0.169 Source

Ward K.A.,Medical Research Council Human Nutrition Research | Ward K.A.,University of Manchester | Das G.,Central Manchester Primary Care National Health Service NHS Trust | Roberts S.A.,University of Manchester | And 5 more authors.
Journal of Clinical Endocrinology and Metabolism

Context: There has been a resurgence of vitamin D deficiency rickets throughout the developed world, with infants and adolescents being primarily affected. Adolescence is a crucial period for muscle and bone mineral accumulation. Objective: The aim was to determine the effect of vitamin D supplementation on the adolescent musculoskeletal system. Design and Setting: We conducted a community-based, double-blind, randomized controlled trial in a secondary school. Participants: Postmenarchal 12- to 14-yr-old females participated in the trial. Ninety-nine were screened, 73 were included in randomized controlled trial, and 69 completed the trial. There were no adverse events. Intervention: Four doses of 150,000 IU vitamin D2 (ergocalciferol) were given over 1 yr. Main Outcome Measures: Dual-energy x-ray absorptiometry, peripheral quantitative computed tomography, and jumping mechanography were used. Results: At follow-up, 25-hydroxyvitamin D [25(OH)D] status was 56.0 ± 8.9 nmol/liter in the intervention group and 15.8 ± 6.6 nmol/liter in controls. There were no effects of supplementation on bone; however, for muscle function, efficiency of movement improved in the vitamin D-treated group. There was an interaction between baseline 25(OH)D concentration and response to vitamin D supplementation for muscle jump velocity. Conclusions: Despite improvements in 25(OH)D status, treatment with vitamin D2 was not shown to increase mineral accretion, bone geometry or strength, muscle force, or power. There were greater increases in jump velocity in girls with the lowest baseline 25(OH)D concentrations. Lack of effect of intervention after the period of peak mineral and muscle mass accretion suggests that earlier action is required. Copyright © 2010 by The Endocrine Society. Source

Lang I.,University of Tubingen | Busche P.,University of Tubingen | Rakhimi N.,University of Tubingen | Rawer R.,Novotec Medical GmbH | Martin D.D.,University of Tubingen
Journal of Musculoskeletal Neuronal Interactions

Objective:We sought to study and procure reference values for weight-related maximum isometric grip force (MIGF), maximum voluntary force in relation to body weight (Fmvrel) and peak whole body stiffness (pKwb) in multiple one-legged hopping (m1LH) in childhood. Methods: We examined 868 children and adolescents (436 female) aged 3 to 19 yrs. Weight related results are reported as multiples of earth's gravity (g). Results: MIFG and Fmvm1LH are highly linearly correlated with body weight. After adjustment for weight, mean Fmvrelm1LH increases from the age of 3 to 6 yrs, then remains at 3.33 g (SD 0.31 g) between 6 and 19 yrs, independent of age and gender. The difference between legs decreases from 10% at 3 yrs to a constant 5.5% after the age of 7 yrs. Weight-adjusted MIGF also increases steeply from 3 to 6 yrs, then shows a further linear, less steep increase - in males through to age 19 yrs while females show a near-standstill after the age of 12 yrs. pKwbm1LH increases from the age of 7 yrs. Conclusion: This data from normal children from a healthy Caucasian population provide a reference for tests of motor function. Source

Busche P.,University of Tubingen | Rawer R.,Novotec Medical GmbH | Rakhimi N.,University of Tubingen | Lang I.,University of Tubingen | Martin D.D.,University of Tubingen
Journal of Musculoskeletal Neuronal Interactions

Objective: We sought to procure age-and gender-related reference data and study the characteristics of body weight related peak force (pFrel), body mass related peak power (pPrel) for counter movement jumps (single two-legged jumps, s2LJ) and chair rising tests (CRT) in children. Methods:We examined 868 healthy participants (436 female) aged 3 to 19 years. Weight-related results of the s2LJ and CRT Mechanography parameters were reported. Results: pPrel during s2LJ (pPrels2LJ) increased linearly with age for males age 5 to 19 and female age 5 to 11 at a rate of 4.6 W/kg per year. pPrels2LJ for females age 12 to 19 increased only by 2.5 W/kg. CRT time per repetition was 1.065 s, independent of age and gender. pPrel per body mass during the rise phase (pPrelCRT) showed similar but smaller age and gender relations as peak power during s2LJ. pFrel was 2.5 g (multiples of earth's gravity) for s2LJ and 1.5 g for CRT. Conclusion: This data from normal children from a healthy Caucasian population provide reference values for tests that reflect everyday motor function. Source

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