Interaction of body fat percentage and height with appendicular functional muscle-bone unit

The interaction of body fat percentage and height with appendicular BMC for LBM was analyzed. Only body fat had significant negative correlation with the appendicular BMC for LBM.

PURPOSE/INTRODUCTION

For the clinical evaluation of the functional muscle-bone unit, it was proposed to evaluate the adaptation of the bone to the acting forces. A frequently used parameter for this is the total body less head bone mineral content (TBLH-BMC) determined by dual-energy X-ray absorptiometry (DXA) in relation to the total body lean body mass (LBM). Body fat percentage seemed to correlate negatively and height positively with TBLH-BMC for LBM. It was supposed that appendicular BMC for LBM is a more accurate surrogate for the functional muscle-bone unit since appendicular LBM does not incorporate the mass of internal organs. The aim of this study was to analyze the interaction of body fat percentage and height with appendicular BMC for LBM.

METHODS

As part of the National Health and Nutrition Examination Survey (NHANES) study, between the years 1999 and 2004, whole-body DXA scans on randomly selected Americans from 8 years of age were carried out. From all eligible DXA scans, three major US ethnic groups were evaluated (non-Hispanic Whites, non-Hispanic Blacks, and Mexican Americans) for further statistical analysis.

RESULTS

For the statistical analysis, the DXA scans of 8190 non-Hispanic White children and adults (3903 female), of 4931 non-Hispanic Black children and adults (2250 female), and 5421 of Mexican American children and adults (2424 female) were eligible. Only body fat had a significant negative correlation with the appendicular BMC for LBM.

CONCLUSIONS

Only body fat had significant negative correlation with appendicular BMC for LBM, and thus, should be addressed when evaluating functional muscle-bone unit.

Individualized evaluation of lumbar bone mineral density and bone mineral apparent density in children and adolescents

Lumbar spine bone mineral density (LS-BMD) assessed by dual-energy X-ray absorptiometry (DXA) is used in children to evaluate bone health. LS-BMD results in children are influenced significantly by height and BMI. An adjustment for these parameters may improve the clinical use of the method.

PURPOSE/INTRODUCTION

DXA evaluation is considered useful in children to assess bone health. For this purpose, lumbar spine bone mineral density (LS-BMD) and bone mineral apparent density (LS-BMAD) are often used. The aim of the study was to estimate the effect of height and BMI on LS-BMD and LS-BMAD in children and adolescents and to develop a method to adjust individual results for these factors.

METHODS

As part of the National Health and Nutrition Examination Survey (NHANES) study, between the years 2005 and 2010 lumbar DXA scans on randomly selected Americans from 8 to 20 years of age were carried out. From all eligible DXA scans, three major US ethnic groups were evaluated (Non-Hispanic Whites, Non-Hispanic Blacks, and Mexican Americans) for further statistical analysis. The relationship between height as well as BMI for age Z-scores and age-adjusted LS-BMD and LS-BMAD Z-scores was analyzed.

RESULTS

For the statistical analysis, the DXA scans of 1799 non-Hispanic White children (823 females), of 1696 non-Hispanic Black children (817 females), and of 1839 Mexican American children (884 females) were eligible. The statistical analysis showed that taller and heavier children had significantly (p < 0.001) higher age-adjusted LS-BMD Z-scores than shorter and lighter children. But on LS-BMAD, only BMI and not height had a significant influence.

CONCLUSIONS

LS-BMD results in children were influenced significantly by their height and BMI, the LS-BMAD results were only influenced by their BMI. For the first time, the proposed method adjusts LS-BMD and LS-BMAD to BMI. An adjustment of the LS-BMD and LS-BMAD results to these factors might improve the clinical significance of an individual result.

Are there effects of age, gender, height, and body fat on the functional muscle-bone unit in children and adults?

The aim was to describe the effect of age, gender, height, different stages of human life, and body fat on the functional muscle-bone unit. All these factors had a significant effect on the functional muscle-bone unit and should be addressed when assessing functional muscle-bone unit in children and adults.

INTRODUCTION

For the clinical evaluation of the functional muscle-bone unit, it was proposed to evaluate the adaptation of the bone to the acting forces. A frequently used parameter for this is the total body less head bone mineral content (TBLH-BMC) determined by dual-energy X-ray absorptiometry (DXA) in relation to the lean body mass (LBM by DXA). LBM correlates highly with muscle mass. Therefore, LBM is a surrogate parameter for the muscular forces acting in everyday life. The aim of the study was to describe the effect of age and gender on the TBLH-BMC for LBM and to evaluate the impact of other factors, such as height, different stages of human life, and of body fat.

METHODS

As part of the National Health and Nutrition Examination Survey (NHANES) study, between the years 1999-2006 whole-body DXA scans on randomly selected Americans from 8 years of age were carried out. From all eligible DXA scans (1999-2004), three major US ethnic groups were evaluated (non-Hispanic Whites, non-Hispanic Blacks, and Mexican Americans) for further statistical analysis.

RESULTS

For the statistical analysis, the DXA scans of 8190 non-Hispanic White children and adults (3903 female), of 4931 non-Hispanic Black children and adults (2250 female) and 5421 of Mexican-American children and adults (2424 female) were eligible. Age, gender, body height, and especially body fat had a significant effect on the functional muscle-bone unit.

CONCLUSIONS

When assessing TBLH-BMC for LBM in children and adults, the effects of age, gender, body fat, and body height should be addressed. These effects were analyzed for the first time in such a large cohort.

Experience with jumping mechanography in children with cerebral palsy

OBJECTIVES

Jumping mechanography provides robust motor function indicators among healthy children. The aim of the study was to assess the reproducibility and validity of jumping mechanography conducted as single two-legged jump (S2LJ) in children with cerebral palsy (CP).

METHODS

215 S2LJ investigations from a sample of 75 children with CP were eligible for evaluation. For the estimation of the reproducibility, only the baseline set of data per patient were used. Gross motor function was evaluated by the Gross Motor Function Measure (GMFM-66). In 135 S2LJ investigations, GMFM-66 was assessed within a week in the same child. This data was used for validity assessment.

RESULTS

Coefficients of variation for the main outcome parameters ranged between 6.15-9.71%, except for jump height (CV%=27.3%). The intraclass correlation coefficients for peak velocity (V_max) and peak power relative to body weight (P_max/mass) was 0.927 and 0.931. V_max and P_max/mass were also the test parameters with the strongest correlation to the GMFM-66 score (⟩0.7).

CONCLUSIONS

S2LJ assessed in the present study provided reproducible outcome measures particularly for Vmax and Pmax/mass in children with CP. Further, V_max and P_max/mass showed the strongest correlation with the GMFM-66 score and seem to be the most relevant evaluation criteria.

The functional muscle-bone unit in children with cerebral palsy

Our results suggest that the prevalence of bone health deficits in children with CP was overestimated, when using only age- and height-adjusted bone mineral content (BMC) and areal bone mineral density (aBMD). When applying the functional muscle-bone unit diagnostic algorithm (FMBU-A), the prevalence of positive results decreased significantly. We recommend applying the FMBU-A when assessing bone health in children with CP.

INTRODUCTION

The prevalence of bone health deficits in children with cerebral palsy (CP) might be overestimated because age- and height-adjusted reference percentiles for bone mineral content (BMC) and areal bone mineral density (aBMD) assessed by dual-energy X-ray absorptiometry (DXA) do not consider reduced muscle activity. The aim of this study was to compare the prevalence of positive DXA-based indicators for bone health deficits in children with CP to the prevalence of positive findings after applying a functional muscle-bone unit diagnostic algorithm (FMBU-A) considering reduced muscle activity.

METHODS

The present study was a monocentric retrospective analysis of 297 whole body DXA scans of children with CP. The prevalence of positive results of age- and height-adjusted BMC and aBMD defined as BMC and aBMD below the P3 percentile and of the FMBU-A was calculated.

RESULTS

In children with CP, the prevalence of positive results of age-adjusted BMC were 33.3% and of aBMD 50.8%. Height-adjusted results for BMC and aBMD were positive in 16.8 and 36.0% of cases. The prevalence of positive results applying the FMBU-A regarding BMC and aBMD were significantly (p < 0.001) lower than using age- and height-adjusted BMC and aBMD (8.8 and 14.8%).

CONCLUSIONS

Our results suggest that the prevalence of bone health deficits in children with CP was overestimated, when using age- and height-adjusted BMC and aBMD. When applying the FMBU-A, the prevalence decreased significantly. We recommend applying the FMBU-A when assessing bone health in children with CP.

Changes in muscle cross-sectional area, muscle force, and jump performance during 6 weeks of progressive whole-body vibration combined with progressive, high intensity resistance training

OBJECTIVES

We hypothesized that progressive whole-body vibration (WBV) superimposed to progressive high intensity resistance training has greater effects on muscle cross-sectional area (CSA), muscle force of leg muscles, and jump performance than progressive high intensity resistance training alone.

METHODS

Two groups of healthy male subjects performed either 6 weeks of Resistive Vibration Exercise (RVE, squats and heel raises with WBV, n=13) or Resistive Exercise (RE, squats and heel raises without WBV, n=13). Squats under RVE required indispensable weight loading on the forefoot to damp harmful vibrations to the head. Time, intervention, and interaction effects were analyzed.

RESULTS

After 6 weeks of training, knee extensor CSA, isometric knee extension force, and counter movement jump height increased equally in both groups (time effect, P⟨0.001, P≤0.02, and P≤0.03, respectively), whereas only in RVE ankle plantar flexor CSA and isometric ankle plantar flexion force reached significance or a tendency, respectively, (time effect, P=0.015 and P=0.069, respectively; intervention effect also for the latter, P=0.006). Drop jump contact time did significantly more improve in RVE (interaction effect, P=0.042).

CONCLUSIONS

RVE showed better training effects than RE only in plantar flexor muscles. RVE seems to be suitable in professional sports with a special focus on calf muscles.

Early vibration assisted physiotherapy in toddlers with cerebral palsy - a randomized controlled pilot trial

OBJECTIVES

to investigate feasibility, safety and efficacy of home-based side-alternating whole body vibration (sWBV) to improve motor function in toddlers with cerebral palsy (CP).

METHODS

Randomized controlled trial including 24 toddlers with CP (mean age 19 months (SD±3.1); 13 boys).

INTERVENTION

14 weeks sWBV with ten 9-minute sessions weekly (non-individualized). Group A started with sWBV, followed by 14 weeks without; in group B this order was reversed. Feasibility (≥70% adherence) and adverse events were recorded; efficacy evaluated with the Gross Motor Function Measure (GMFM-66), Pediatric Evaluation of Disability Inventory (PEDI), at baseline (T0), 14 (T1) and 28 weeks (T2).

RESULTS

Developmental change between T0 and T1 was similar in both groups; change scores in group A and B: GMFM-66 2.4 (SD±2.1) and 3.3 (SD±2.9) (p=0.412); PEDI mobility 8.4 (SD±6.6) and 3.5 (SD±9.2) (p=0.148), respectively. In two children muscle tone increased post-sWBV. 24 children received between 67 and 140 sWBV sessions, rate of completed sessions ranged from 48 to 100% and no dropouts were observed.

CONCLUSION

A 14-week home-based sWBV intervention was feasible and safe in toddlers with CP, but was not associated with improvement in gross motor function.

Reactions of the rat musculoskeletal system to compressive spinal cord injury (SCI) and whole body vibration (WBV) therapy

Traumatic spinal cord injury (SCI) causes a loss of locomotor function with associated compromise of the musculo-skeletal system. Whole body vibration (WBV) is a potential therapy following SCI, but little is known about its effects on the musculo-skeletal system. Here, we examined locomotor recovery and the musculo-skeletal system after thoracic (T7-9) compression SCI in adult rats. Daily WBV was started at 1, 7, 14 and 28 days after injury (WBV1-WBV28 respectively) and continued over a 12-week post-injury period. Intact rats, rats with SCI but no WBV (sham-treated) and a group that received passive flexion and extension (PFE) of their hind limbs served as controls. Compared to sham-treated rats, neither WBV nor PFE improved motor function. Only WBV14 and PFE improved body support. In line with earlier studies we failed to detect signs of soleus muscle atrophy (weight, cross sectional diameter, total amount of fibers, mean fiber diameter) or bone loss in the femur (length, weight, bone mineral density). One possible explanation is that, despite of injury extent, the preservation of some axons in the white matter, in combination with quadripedal locomotion, may provide sufficient trophic and neuronal support for the musculoskeletal system.

Neuromuscular training based on whole body vibration in children with spina bifida: a retrospective analysis of a new physiotherapy treatment program

INTRODUCTION

Spina bifida is the most common congenital cause of spinal cord lesions resulting in paralysis and secondary conditions like osteoporosis due to immobilization. Physiotherapy is performed for optimizing muscle function and prevention of secondary conditions. Therefore, training of the musculoskeletal system is one of the major aims in the rehabilitation of children with spinal cord lesions.

INTERVENTION AND METHODS

The neuromuscular physiotherapy treatment program Auf die Beine combines 6 months of home-based whole body vibration (WBV) with interval blocks at the rehabilitation center: 13 days of intensive therapy at the beginning and 6 days after 3 months. Measurements are taken at the beginning (M0), after 6 months of training (M6), and after a 6-month follow-up period (M12). Gait parameters are assessed by ground reaction force and motor function by the Gross Motor Function Measurement (GMFM-66). Sixty children (mean age 8.71 ± 4.7 years) who participated in the program until February 2014 were retrospectively analyzed.

RESULTS

Walking velocity improved significantly by 0.11 m/s (p = 0.0026) and mobility (GMFM-66) by 2.54 points (p = 0.001) after the training. All changes at follow-up were not significant, but significant changes were observed after the training period. Decreased contractures were observed with increased muscle function.

CONCLUSION

Significant improvements in motor function were observed after the active training period of the new neuromuscular training concept. This first analysis of the new neuromuscular rehabilitation concept Auf die Beine showed encouraging results for a safe and efficient physiotherapy treatment program which increases motor function in children with spina bifida.

A specialized rehabilitation approach improves mobility in children with osteogenesis imperfecta

OBJECTIVE

Osteogenesis imperfecta (OI) is a rare disease leading to recurrent fractures, hyperlaxicity of ligaments, short stature and muscular weakness. Physiotherapy is one important treatment approach. The objective of our analysis was to evaluate the effect of a new physiotherapy approach including side alternating whole body vibration on motor function in children with OI.

METHODS

In a retrospective analysis data of 53 children were analyzed. The 12 months approach included 6 months of side alternating whole body vibration training, concomitant physiotherapy, resistance training, treadmill training and 6 months follow up. Primary outcome parameter was the Gross Motor Function Measure after 12 months (M12).

RESULTS

53 children (male: 32; age (mean±SEM): 9.1±0.61, range 2.54-24.81 years) participated in the treatment approach. A significant increase of motor function (GMFM-66 score 55.47±2.45 to 58.67±2.83; p=0.001) and walking distance (47.04 m±6.52 to 63.36±8.25 m (p<0.01) between M0 and M12 was seen. Total body without head bone mineral density increased significantly at M12 (p=0.0189).

CONCLUSIONS

In the cohort of OI children which participated in the specialized treatment approach improvements of motor function were observed. Therefore this program should be considered as additional therapeutic approach for children with severe OI.

[Secondary forms of osteoporosis. Special features of diagnostics in childhood and adolescence]

Rheumatic diseases in childhood and adolescence can lead to secondary osteoporosis based on various pathophysiologies. The underlying disease, medication and immobility resulting in a reduced osteoanabolic stimulus contribute to the development of a fragile skeletal system. For diagnostic purposes dual-energy X-ray absorptiometry (DXA) is the most frequently used technology. For interpretation of the areal bone mineral density, age and gender matched reference data have to be used. Particularly in the pediatric field, body height must additionally be taken into consideration. Further techniques which can provide detailed information are peripheral quantitative computed tomography and high resolution magnetic resonance imaging. Nowadays, skeletal assessments have to be interpreted in the context of the muscular system. The concept of the functional muscle-bone unit is widely accepted and uses the muscles as the dominating factor. In a second step the adaptation of the skeletal system to the applied muscle force is evaluated. This allows a differentiation between primary and secondary skeletal diseases depending on the ratio of muscles to bone. Therapeutic options for secondary osteoporosis include reduction of the causative medication, treatment of the underlying disease, antiresorptive treatment with bisphosphonates and different programs to activate the muscles. A multimodal interval rehabilitation program including alternating side vibration shows positive effects on mobility, muscle function and bone mass in children and adolescents.

Personalized approach to growth hormone treatment: clinical use of growth prediction models

The goal of growth hormone (GH) treatment in a short child is to attain a fast catch-up growth toward the target height (TH) standard deviation score (SDS), followed by a maintenance phase, a proper pubertal height gain, and an adult height close to TH. The short-term response variable of GH treatment, first-year height velocity (HV) (cm/year or change in height SDS), can either be compared with GH response charts for diagnosis, age and gender, or with predicted HV based on prediction models. Three types of prediction models have been described: the Kabi International Growth Hormone Study models, the Gothenburg models and the Cologne model. With these models, 50-80% of the variance could be explained. When used prospectively, individualized dosing reduces the variation in growth response in comparison with a fixed dose per body weight. Insulin-like growth factor-I-based dose titration also led to a decrease in the variation. It is uncertain whether adding biochemical, genetic or proteomic markers may improve the accuracy of the prediction. Prediction models may lead to a more evidence-based approach to determine the GH dose regimen and may reduce the drug costs for GH treatment. There is a need for user-friendly software programs to make prediction models easily available in the clinic.

Randomized controlled study on resistive vibration exercise (EVE study): protocol, implementation and feasibility

OBJECTIVES

A training intervention comparing resistance exercise with or without whole-body vibration (WBV) was conducted to compare acute and chronic effects on functional and molecular parameters.

METHODS

A six-week training intervention was performed including 26 healthy males (26 years, SD=4). Two groups were analyzed in a parallel design performing either resistive exercise (RE, n=13) or resistive vibration exercise (RVE, n=13) training with weekly increasing vibration frequencies (20-40Hz). Resting and exercising blood pressure and heart rate were measured before and after the 6-week intervention.

RESULTS

Both training interventions decreased resting systolic blood pressure (P=0.003). Resting diastolic blood pressure was significantly decreased only in the RVE group (P=0.01). Exercising diastolic blood pressure was significantly decreased during the final training (P<0.001) with no additional effect of superimposed vibrations. Resistance exercise with superimposed vibrations evoked back pain to a higher degree than resistance exercise alone when training at frequencies above 30Hz (P<0.01).

CONCLUSIONS

These data suggest positive effects of resistance exercise upon cardiovascular health and vascular responsiveness and a further beneficial effect of superimposed vibrations in decreasing resting diastolic blood pressure. Finally, development of back pain may be fostered by superimposed vibrations to high training loads, particularly at higher frequencies.

First use of the RANKL antibody denosumab in osteogenesis imperfecta type VI

Osteogenesis imperfecta (OI) is a genetically heterogeneous disease leading to bone fragility. OI-VI is an autosomal-recessive form caused by mutations in SERPINF1. There is experimental evidence suggesting that loss of functional SERPINF1 leads to an activation of osteoclasts via the RANK/RANKL pathway. Patients with OI-VI show a poor response to bisphosphonates. We report on four children with OI-VI who had shown continuously elevated urinary bone resorption markers during a previous treatment with bisphosphonates. We treated these children with the RANKL antibody denosumab to reduce bone resorption.

INTERVENTION AND RESULTS

Denosumab (1 mg/kg body weight) was injected s.c. every 3 months. There were no severe side effects. Markers of bone resorption decreased to the normal range after each injection. N-terminal Propeptide of collagen 1 was measured in the serum during the first treatment cycle and decreased also. Urinary deoxypyridinoline/creatinine was monitored in a total of seven treatment cycles and indicated that bone resorption reached the pre-treatment level after 6-8 weeks.

CONCLUSION

This was the first use of denosumab in children with OI-VI. Denosumab was well tolerated, and laboratory parameters provided evidence that the treatment reversibly reduced bone resorption. Therefore, denosumab may be a new therapeutic option for patients with OI-VI.

Reshaping of vertebrae during treatment with neridronate or pamidronate in children with osteogenesis imperfecta

BACKGROUND/AIMS

Osteogenesis imperfecta (OI) is a hereditary disease causing increased bone fragility. Pamidronate (PAM), which has to be administered as a 3-day course according to the original protocol by Glorieux, is the most frequently used therapy. Other bisphosphonates like neridronate (NER), which can be infused during an outpatient visit, have also proven to be effective. This is the first analysis comparing the effect of PAM and NER using vertebral morphometry.

METHODS

28 patients with OI type III and IV were retrospectively analyzed by matched pairs.

RESULTS

No differences were detected between patients treated with PAM or NER at the start of therapy: mean age 4.4 years (p = 0.730), mean height 86.8 cm/85.3 cm (p = 0.854), lumbar vertebral area 208.9 mm(2)/206.0 mm(2) (p = 0.555), and in all vertebral indices. After 1 year of treatment (mean 1.16 years; p = 0.854) both groups showed a significant increase in the vertebral area and improved vertebral indices. Again there were no differences between the groups in the vertebral area (p = 0.590).

CONCLUSION

In this study there was no difference between patients treated with PAM or NER regarding vertebral morphometry during the first year of therapy. Because of the possibility of an outpatient setting, NER is convenient for these children.

Reporting whole-body vibration intervention studies: recommendations of the International Society of Musculoskeletal and Neuronal Interactions

Whole-body vibration (WBV) is receiving increasing interest as a therapeutic modality to improve neuromuscular performance or to increase bone mass or density. In order to help improve the quality of reports about WBV treatment studies, the International Society of Musculoskeletal and Neuronal Interactions (ISMNI) invited experts in the field to provide suggestions on how the intervention should be described in such reports. The recommendations are presented here.

Effect of a new physiotherapy concept on bone mineral density, muscle force and gross motor function in children with bilateral cerebral palsy

OBJECTIVE

The purpose of this study was to determine the effect of a new physiotherapy concept on bone density, muscle force and motor function in bilateral spastic cerebral palsy children.

METHODS

In a retrospective data analysis 78 children were analysed. The concept included whole body vibration, physiotherapy, resistance training and treadmill training. The concept is structured in two in-patient stays and two periods of three months home-based vibration training. Outcome measures were dual-energy x-ray absorption (DXA), Leonardo Tilt Table and a modified Gross Motor Function Measure before and after six months of training.

RESULTS

Percent changes were highly significant for bone mineral density, -content, muscle mass and significant for angle of verticalisation, muscle force and modified Gross Motor Function Measure after six months training.

CONCLUSIONS

The new physiotherapy concept had a significant effect on bone mineral density, muscle force and gross motor function in bilateral spastic cerebral palsy children. This implicates an amelioration in all International Classification of Functioning, Disability and Health levels. The study serves as a basis for future research on evidence based paediatric physiotherapy taking into account developmental implications.

Mechanographic analyses in pediatrics: allometric scaling of 'peak jump force' and its relationship to 'maximal isometric grip force' in childhood and adolescence

BACKGROUND

Kinetic analyses of the neuromuscular system have become an important part in the diagnostics of metabolic bone disorders in pediatrics because of the relevance of the 'Functional Muscle-Bone Unit'. Because muscle function is associated with muscle metabolism, it is suggested that the association of maximal forces with anthropometric variables (e. g., body weight) is characterized by allometric scaling. The present manuscript aims to describe the scaling exponent for the association of maximal forces of mechanography and dynamometry to body weight and exemplarily applies the prediction of 'Peak Jump Force' (PJF) by 'Maximal Isometric Grip Force' (MIGF) for the characterization of the unconditioned neuromuscular system in subjects with congenital heart disease (CHD).

SUBJECTS

MIGF was measured in a reference population of 135 school boys and 177 school girls who were not randomized individuals of a German primary and high-school. In addition, data of the neuromuscular system were analyzed in 29 individuals with CHD.

METHODS

Participants performed counter-movement jumping on a force plate to measure PJF and v (max). MIGF was determined by dynamometric measurement.

RESULTS

PJF scaled (body mass) (0.97) in girls and (body mass) (1.05) in boys. PJF was not different from the scaling exponent=1 in both genders. After having taken the logarithm, MIGF predicted PJF with R (2)(adjusted)=0.774 in boys, R (2)(adjusted)=0.720 in girls (p<0.001 each) and R (2)(adjusted)=0.209 (p=0.007) in patients with CHD. The mean of the predicted PJF was lower than the mean of the measured PJF in subjects with CHD (p<0.001). The difference between the predicted and the measured PJF (DeltaPJF) was associated with v (max) (R (2)(adjusted)=0.113, p=0.042).

CONCLUSIONS

PJF scales body weight in an isometric way as recently describe for other vertebrates. MIGF is a good predictor of PJF in healthy children, but not in unconditioned individuals. DeltaPJF indicates conditioning of the individual and may be used to describe inter- and intramuscular coordination in children. HINTERGRUND: Mechanografische Analysen des neuromuskulären Systems haben mittlerweile auch einen diagnostischen Stellenwert in der Pädiatrie erlangt. Ziel der vorliegenden Untersuchung ist die kinetische Analyse des Counter-movement-Sprungs durch die Messung der Bodenreaktionskräfte in Hinblick auf seine allometrische Skalierung und im Vergleich zur Entwicklung der ,Maximalen isometrischen Griffstärke' (MIGF) bei Kindern und Jugendlichen. PROBANDEN: Die Studienpopulation umfasste 135 Schüler und 177 Schülerinnen, die nicht randomisiert wurden und Schüler einer deutschen Grundschule und eines deutschen Gymnasiums waren. Zudem wurden Daten von 29 Patienten mit kongenitalen Herzfehlern analysiert.

METHODEN

Die Studienteilnehmer absolvierten Counter-movement-Sprünge auf einer Sprungplatte, sodass die maximale Sprungkraft (Peak Jump Force, PJF) und die maximale Geschwindigkeit des Massenschwerpunktes beim Absprung (v (max)) ermittelt werden konnten. MIGF wurde durch Messung mit einem Dynamometer bestimmt. ERGEBNISSE: PJF-skalierte (Körpermasse) (0,97) bei den Mädchen und (Körpermasse) (1,05) bei den Jungen. Der Skalierungsfaktor von PJF war bei Mädchen und Jungen nicht signifikant vom Faktor=1 verschieden. Nach Lograithmierung sagte die Variable MIGF den Parameter PJF in der Gruppe der Jungen mit R (2)(adjusted)=0,774, in der Gruppe der Mädchen mit R (2)(adjusted)=0,720 (jeweils p<0,001) und in der Gruppe der Herzkranken mit R (2)(adjusted)=0,209 (p=0,007) voraus. Der Mittelwert des vorhergesagten Wertes für PJF war niedriger als der Wert der gemessenen PJF in Patienten mit Herzerkrankung (p<0,001). Die Differenz zwischen vorhergesagter und gemessener PJF (DeltaPJF) stand statistisch mit v (max) (R (2)(adjusted)=0,113; p=0,042) in Zusammenhang. SCHLUSSFOLGERUNGEN: PJF skaliert isometrisch zur Körpermasse, wie es bereits für andere Vertebraten beschrieben wurde. MIGF ist ein guter Prädiktor für PJF bei gesunden Kindern und Jugendlichen, jedoch nicht bei Menschen mit einem unkonditionierten neuromuskulären System. DeltaPJF kann als Marker für die Konditionierung eines neuromuskulären Systems angesehen werden und beschreibt inter- und intramuskuläre Koordination.

Mechanical influences on bone development in children

This review focuses on methodological concepts in the evaluation of skeletal muscle function and on adaptation. It is now thought that the critical property of bone is strength rather than weight, and that control of bone strength is mainly exercised through the effect of the mechanical loads brought to bear on bone. Muscle contraction places the greatest physiological load on bone, and so the stability of bone must be adapted to muscle strength (the functional muscle-bone unit). The described suggestions and recommendations outline a new concept: bone mass and strength should not be related to age. There is now more and more evidence that bone mass and strength should be related to muscle function. Thus analyzed, there is no such entity as 'peak bone mass'. Many studies are presently under way to evaluate whether these novel approaches increase the sensitivity and specificity of fracture prediction in an individual. Furthermore, the focus of many bone researchers is shifting away from bone mass to bone geometry or bone strength and their relationship with the driving muscle system.

Peripheral quantitative computed tomography of the proximal radius in young subjects--new reference data and interpretation of results

The aim of this contribution is to provide reference data for peripheral quantitative computed tomography (Stratec XCT2000) performed at the proximal radius (the so-called '65% site') of young subjects and to discuss the interpretation of such analyses. Data from a previous reference data study on 469 subjects between 6 and 40 years were re-analyzed and smooth curves were fitted. The corresponding equations allow for calculation of age-, height- and sex-specific z-scores of total cross-sectional area, cortical cross-sectional area, bone mineral content, cortical bone mineral density, total bone mineral density, Strength-Strain Index, muscle cross-sectional area and the ratio between bone mineral content and muscle cross-sectional area. These data should facilitate the clinical use of peripheral quantitative computed tomography in young subjects.

The influence of auxology and long-term glycemic control on muscle function in children and adolescents with type 1 diabetes mellitus

We intended to investigate in this pilot-study if long-term glycemic control stands in close relationship with muscle function in children and adolescents with type 1 diabetes mellitus (T1DM). Muscle function (MIGF, maximal isometric grip force; PJF, peak jump force; PJP, peak jump power) was investigated in 40 children and adolescents (males 20, females 20; age 13.5-/+2.5 yr) affected with T1DM. Muscular parameters were correlated with anthropometric parameters (age, height, weight) and with glycosylated hemoglobin (HbA1c) of the presence and the past. Standard deviation scores (SDSs) of weight and MIGF indicated significantly higher weight (mean 0.75-/+1.83 (SD)) and lower MIGF (mean -1.06-/+1.76 (SD)) in individuals with T1DM. When the study group was divided into two groups by the criteria that the actual HbA1c (HbA1c0) was lower (N=25) or higher (N=15) than 8.5%, the comparison showed significantly higher muscular parameters (PJF-SDS, PJP-SDS and MIGF-SDS) in individuals with higher HbA1c0. Multiple regression analyses demonstrated that body weight and height primarily predicted muscle force (MIGF, PJF) in T1DM. In conclusion, skeletal growth is an important determinant for the development of muscle function in children and adolescents with T1DM.

Preliminary results on the mobility after whole body vibration in immobilized children and adolescents

The present article is a preliminary report on the effect of Whole Body Vibration (WBV) on the mobility in long-term immobilized children and adolescents. WBV was applied to 6 children and adolescents (diagnoses: osteogenesis imperfecta, N=4; cerebral palsy, N=1; dysraphic defect of the lumbar spine, N=1) over a time period of 6 months. WBV was applied by a vibrating platform constructed on a tilt-table. The treatment effect was measured by alternations of the tilt-angle of the table and with the "Brief assessment of motor function" (BAMF). All 6 individuals were characterized by an improved mobility, which was documented by an increased tilt-angle or an improved BAMF-score. The authors concluded WBV might be a promising approach to improve mobility in severely motor-impaired children and adolescents. Therefore, the Cologne Standing-and-Walking- Trainer powered by Galileo is a suitable therapeutic device to apply WBV in immobilized children and adolescents.

The Principle of Regulation in Biology - From Bone to Eating Behavior

Cell physiology and molecular biology typically follow a reductionistic approach in science. In the last decade, molecular principles and pathogenetic factors involved in the development of many diseases have been successfully discovered. Therefore, early biological concepts based on systemic and cybernetic thoughts have been largely overshadowed by these more recent molecular and pathogenetic factors. This review highlights discoveries on bone development and hypothalamic controlled feeding and eating behavior with a cybernetic and systemic perspective. Interestingly, ancient ideas on bone development and hypothalamic function are still reasonable considerations to embed new molecular discoveries into a systemic concept of principles organizing nature.

The muscle-bone unit in adulthood: influence of sex, height, age and gynecological history on the bone mineral content and muscle cross-sectional area

Bone and muscle development are both strongly influenced by sex hormones. The purpose of this study was to examine the changes in bone and muscle parameters (bone mineral content - BMC, muscle cross-sectional area - MA) in 130 men aged 31 -60 years, and in 180 pre-menopausal women aged 30-53 years with respect to age, body height and, with the women, their gynecological history (age-at-menarche, number of pregnancies, duration of lactation and use of oral contraception). The study was performed using peripheral quantitative computed tomography (pQCT) at a 65% site of the forearm length. Both BMC and MA were dependent on body height (p<0.0001), but not on age. The BMC/MA ratio was dependent neither on age nor on body height in both genders. MA as well as BMC were found significantly higher in males than in females (p<0.0001 for both variables). We observed a significantly higher BMC/MA ratio in females than in males (p<0.0001). We found no effect either of the analyzed variables of gynecological history on bone/muscle characteristics. The findings highlight the necessity of involving height-adjusted parameters and BMC/MA ratio into bone analysis in adults.

Different effects of agonistic vs. antagonistic gnrh-analogues (triptorelin vs. cetrorelix) on bone modeling and remodeling in peripubertal female rats

Little is known about the effects of antagonistic GnRH analogues vs. agonists on bone strength, specifically in context of treating precocious puberty. Peripubertal female rats were treated from postnatal day 25 - 36 with either the GnRH agonist triptorelin (TRIP) or the antagonist cetrorelix (CET). Using peripherial quantitative computerized tomography (pQCT) we investigated effects on bone parameters. Onset of puberty was retarded by both analogues as measured by prevention of vaginal opening at 36 d of age and reduced uterine weights. In the tibia, cortical content, cortical area related to body weight, and periosteal circumference related to weight were significantly reduced in CET-treated rats - indicating reduced bone modeling and reduced bone strength (cortical circumference related to body weight: CET 0.066 +/- 0.001 vs. TRIP 0.068 +/- 0.001 vs. controls 0.071 +/- 0.001 mm/g, mean +/- SEM, p < 0.05 CET vs. controls; cortical area related to body weight: CET 3.87 +/- 0.46 vs. TRIP 6.80 +/- 0.63 vs. controls 8.07 +/- 1.13, x 10 (-3) mm (2)/g, p < 0.001 CET vs. controls; cortical content: CET 0.316 +/- 0.038 vs. TRIP 0.546 +/- 0.051 vs. controls 0.624 +/- 0.089 mg/mm, p < 0.01 CET vs. controls). In conclusion, although both CET and TRIP inhibit puberty in rats, cortical thinning was only seen in CET-treated rats. This indicates that GnRH antagonist treatment might cause reduced bone strength which is partly comparable to postmenopausal bone loss. When using new GnRH antagonists for treating precocious puberty in humans, parameters for bone strength and mineralization should be monitored.

From mechanostat theory to development of the "Functional Muscle-Bone-Unit"

Bone densitometric data are often difficult to interpret in children and adolescents because of large inter- and intraindividual variations in bone size. Here, we propose a functional approach to bone densitometry that addresses two questions: is bone strength normally adapted to the largest physiological loads, that is, muscle force? Is muscle force adequate for body size? The theoretical background for this approach is provided by the mechanostat theory, which proposes that bones adapt their strength to keep the strain caused by physiological loads close to a set point. Because the largest physiological loads are caused by muscle contractions, there should be a close relationship between bone strength and muscle force or size. The proposed two-step diagnostic algorithm requires a measure of muscle force or size and a measure of bone mineral content (BMC) at a corresponding location. The results can be combined into four diagnostic groups. In the first situation, muscle force or size is adequate for height. If the skeleton is adapted normally to the muscle system, the result is interpreted as "normal". If it is lower than expected for muscle force or size, a "primary bone defect" is diagnosed. In the second situation, muscle force or size is too low for height. Even if the skeleton is adapted adequately to the decreased mechanical challenge, this means that bone mass and presumably strength are still too low for body height. Therefore, a "secondary bone defect" is diagnosed. It is hoped that the more detailed insights thus gained could help to devise targeted strategies for the prevention and treatment of pediatric bone diseases.

Examining the developing skeletal muscle: Why, what and how?

This review focuses on methodological concepts in the evaluation of skeletal muscle function, taking into account classical muscle physiology, the developing motor system in children and anthropometric parameters. Thereby, the classical concept of kinetic and thermodynamic description of muscle function is discussed in relation to data pertaining to human physiology. Emphasis is given to the specific problems that arise when assessing muscle function during development. Two important factors influencing muscle function are discussed in detail: changes in anthropometric characteristics and changes in co-ordinative skills in the developing individual. Finally, we discuss currently available methods for the evaluation of anaerobic muscle function in children and adolescents (maximal isometric grip force, peak jump force, peak jump power, Wingate test, Bosco test).

Seasonality of growth response to GH therapy in prepubertal children with idiopathic growth hormone deficiency

OBJECTIVE

Longitudinal growth of children exhibits seasonal variation. In both healthy children and in children with growth hormone (GH) deficiency (GHD) receiving GH therapy, growth rate is maximal during spring and summer. In the present study, we analyzed the growth response to GH therapy in children with GHD as a function of the season when therapy was started.

SUBJECTS AND METHODS

Anthropometric measurements and biochemical analyses of GH secretion status and bone formation were longitudinally assessed in a cohort of 52 prepubertal children with GHD (14 girls, mean age 7.6 years) who were treated with a fixed dose of GH (0.025 mg/kg/day).

RESULTS

Auxological assessments over the 2-year observation period revealed a significantly better growth response to GH therapy in children who started therapy between the spring and summer (group 1) compared with children who started in the autumn or winter (group 2). The difference was largest in the initial 3-month treatment period (35%; P<0.01). The initial better gain in height of group 1 was sustained during the study period. Baseline peak GH levels during stimulation tests and insuin-like growth factor-I levels did not differ between the two groups. However, group 1 had significantly higher bone resorption and formation markers, either at the start or shortly after initiation of GH treatment. This suggests that children with GHD have higher bone turnover during spring and early summer, irrespective of GH therapy.

CONCLUSIONS

In summary, this study suggests that the season of GH initiation is a determinant of the initial growth response to GH replacement in prepubertal children with GHD.

The bone mass concept: problems in short stature

Bone densitometry is currently one of the mainstays in the evaluation of systemic bone diseases in adults and is also increasingly used to assess primary or secondary bone disorders in children and adolescents. The purpose of carrying out densitometric studies in such circumstances is to measure the densitometric indicators of bone stability. Following procedures which were established for diagnosing adult osteoporosis, a decrease in densitometric surrogates of bone stability is usually interpreted as indicating increased fracture risk. The most basic densitometric parameter is bone mineral content (BMC), which can be measured with most densitometric techniques. BMC is either defined as the mass of mineral contained in an entire bone or as the mass of mineral per unit bone length. While mineral mass can be expected to be a good surrogate for bone stability, BMC is obviously a size-dependent parameter, since small bones weigh less than big bones. This is a drawback in paediatric use, since many children and adolescents who are examined by densitometry suffer from chronic disorders and are small-for-age. Short children will have a lower BMC than their healthy age-matched peers, even if their (smaller) bones are otherwise completely normal.

Muscle mass during childhood--relationship to skeletal development

Bone densitometric data often are difficult to interpret in children and adolescents because of large inter- and intraindividual variations in bone size. Here, we propose a functional approach to bone densitometry that addresses two questions: Is bone strength normally adapted to the largest physiological loads, that is, muscle force? Is muscle force adequate for body size? To implement this approach, forearm muscle cross-sectional area (CSA) and bone mineral content (BMC) of the radial diaphysis were measured in 349 healthy subjects from 6 to 19 years of age (183 girls), using peripheral quantitative computed tomography (pQCT). This functional approach to pediatric bone densitometric data should be adaptable to a variety of densitometric techniques.

From Bone Biology to Bone Analysis

Bone development is one of the key processes characterizing childhood and adolescence. Understanding this process is not only important for physicians treating pediatric bone disorders, but also for clinicians and researchers dealing with postmenopausal and senile osteoporosis. Bone densitometry has great potential to enhance our understanding of bone development. The usefulness of densitometry in children and adolescents would be increased if the physiological mechanisms and structural features of bone were given more consideration in the design and interpretation of densitometric studies. This review gives an overview on the most relevant techniques of quantitative noninvasive bone analysis. Furthermore it describes the relationship between bone biology, selected surrogates describing the biological processes and the possibilities of measuring these surrogates specifically and precisely by the different devices. The overall recommendation for researchers in this field is to describe firstly the biological process to be analyzed (bone growth in length, remodeling or modeling, or all together), secondly the bone parameter which describes this process, and thirdly the reason for selecting a special device.

The regulation of bone development as a biological system

A large number of molecular, cellular, and epidemiologic factors have been implicated in the regulation of bone development. A major unsolved problem is how to integrate these disparate findings into a concept that explains the development of bone as an organ. Often, events at the organ level are simply presented as the cumulative effect of all factors that individually are known to influence bone development. In such a cumulative model it must be assumed that each bone cell carries the construction plan of the entire skeletal anatomy in its genes. This scenario is implausible, because it would require an astronomical amount of positional information. We therefore propose a functional model of bone development, which is based on Frost's mechanostat theory. In this model, the genome only provides positional information for the basic outline of the skeleton as a cartilaginous template. Thereafter, bone cell action is coordinated by the mechanical requirements of the bone.

Influence of puberty on muscle development at the forearm

Despite its fundamental importance for physical development, the growth of the muscle system has received relatively little consideration. In this study, we analyzed the relationship between cross-sectional area (CSA) of forearm muscles and maximal isometric grip force with age and pubertal stage. The study population comprised 366 children, adolescents, and young adults from 6 to 23 yr of age (185 female) and 107 adults (88 female) aged 29 to 40 yr. By use of peripheral quantitative computed tomography, muscle CSA was determined at the site of the forearm, whose distance to the ulnar styloid process corresponded to 65% of forearm length. Both muscle CSA and grip force were higher in prepubertal boys than in girls. The gender differences decreased until pubertal stage 3 and reincreased thereafter. In girls at pubertal stage 5, muscle CSA no longer increased with age (P > 0.4), whereas there was still some age-related increase in grip force (P = 0.02). In boys at pubertal stage 5, both muscle CSA and grip force continued to increase significantly with age (P < 0.005 each). Specific grip force (grip force per muscle CSA) adjusted for forearm length increased by almost one-half between 6 and 20 yr of age, with no difference between the genders. In conclusion, forearm muscle growth takes a gender-specific course during puberty, indicating that it is influenced by hormonal changes. However, the increase in specific grip force is similar in both genders and thus appears to be independent of sex hormones.

Gender-specific pubertal changes in volumetric cortical bone mineral density at the proximal radius

It is well established that puberty affects the geometry of cortical bone differently in females and males. In the present study we investigated whether there are also gender differences in the volumetric bone mineral density of the cortical compartment (BMDcort). BMDcort was determined at the proximal radial diaphysis in 362 healthy children and adolescents (age 6-23 years; 185 females, 177 males) and in 107 adults (age 29-40 years; 88 women, 19 men) using peripheral quantitative computed tomography (pQCT). The densitometric result for BMDcort was similar in prepubertal girls and boys, but was significantly higher in females after pubertal stage 3. pQCT results for BMDcort are influenced by cortical thickness due to the partial volume effect. Therefore, these gender differences were reanalyzed in groups of subjects of the same developmental stage who were matched for cortical thickness. Thus calculated, no gender difference in BMDcort was detected in prepubertal children. However, adolescent females after pubertal stage 3 and adult women had a 3%-4% higher BMDcort than males at the same developmental stage. BMDcort is an integrated measure of both cortical porosity and mean material density of cortical bone. The metabolic activity of cortical bone (intracortical remodeling) increases cortical porosity and decreases the mean material density of cortical bone. Our results therefore suggest that intracortical remodeling is lower in postpubertal females than in males.

Skeletal development in premature infants: a review of bone physiology beyond nutritional aspects

Bone development is usually seen as a process of bone mineral accretion or increase in bone mass, and treatment of bone disorders usually consists of attempts to maximise bone mass accumulation by nutritional means only. However, from a functional perspective, bones should not be as heavy as possible, but rather as stable as necessary. It is therefore important to create conditions that stimulate bones to become more stable.

Peripheral quantitative computed tomography at the distal radius: cross-calibration between two scanners

Peripheral quantitative computed tomography (pQCT) is an important technique to study the interaction between the muscle and bone systems. We have recently established pQCT reference ranges for children, adolescents and young adults using a recent version (XCT 2000) of the Stratec scanners (Stratec Inc., Pforzheim, Germany). However, the previous version of this type of scanner (XCT 900) is still widely used and cross-calibration is needed to use these reference data. Therefore, both distal radii of 19 healthy subjects (age 21 to 59 years; 11 women) were analyzed at the "4% site" using both the XCT 900 and the XCT 2000. Cross-sectional area, total and trabecular bone mineral density (BMD), total bone mineral content (BMC) and polar Strength-Strain Index (SSI) results from the two scanners were compared using linear regression analysis. To achieve scanner calibration we used the intercept and slope of the correlations. The correlation coefficients between the two devices were 0.82 for the cross-sectional area, 0.81 for total BMD, 0.97 for trabecular BMD, 0.99 for total BMC and 0.86 for polar SSI. In conclusion, these data allow for the conversion of XCT 900 results at the distal radius to XCT 2000 values and vice versa.

Analysis of the musculoskeletal system in children and adolescents receiving anticonvulsant monotherapy with valproic acid or carbamazepine

OBJECTIVE

To examine bone development in children and adolescents who have uncomplicated idiopathic epilepsy and had received monotherapy with carbamazepine or valproic acid for at least 1 year.

METHODS

Thirty-nine patients from 6 to 19 years of age (18 girls) were studied. Total bone mineral content (BMC) and trabecular volumetric bone mineral density were measured at the distal radius using peripheral quantitative computed tomography. Maximum isometric grip force was determined with a standard dynamometer. Alkaline phosphatase activity and deoxypyridinoline (a marker of bone resorption) were assessed in serum and urine, respectively.

RESULTS

Trabecular volumetric bone mineral density was significantly decreased in the entire group (z score mean +/- standard deviation: -0.62 +/- 1.04) and in the subgroup using valproic acid (-0.75 +/- 1.18). In the carbamazepine subgroup, there was a similar but nonsignificant trend (-0.50 +/- 0.90). Total BMC and isometric maximum grip force were normal in the entire study population (0.10 +/- 1.22) and in the 2 subgroups. The relationship between BMC and grip force was similar between patients and healthy participants. Urinary levels of deoxypyridinoline were significantly elevated above normal in the whole study population (1.35 +/- 2.00) and in both the valproic acid and the carbamazepine subgroups.

CONCLUSIONS

Bone turnover can be increased, but bone mass is adequate in children and adolescents who have uncomplicated idiopathic epilepsy and who receive monotherapy with carbamazepine or valproic acid.