Udo Meinhardt

High-Intensity Training Increases Spontaneous Physical Activity in Children: A Randomized Controlled Study

OBJECTIVE To test the hypothesis that resistance training may increase spontaneous physical activity in children. STUDY DESIGN Two junior ice hockey teams were randomly assigned to unchanged training schedules (team ZSC, 21 boys; mean age, 13.2 years) or to participate twice weekly in guided resistance training for 4 months (team GCK, 25 boys; mean age, 13.4 years). Spontaneous physical activity energy expenditure (SpAEE; 3-axial accelerometry for 7 days), muscle strength, and body composition (dual energy x-ray absorptiometry) were measured at 0, 4, and 12 months. RESULTS Baseline measures did not differ in the groups, except for higher leg and trunk strength in team ZSC. In the intervention group compared with the control group, SpAEE significantly (P < or = .02) increased at 4 months (+25.5% versus 0%) and 12 months (+13.5% versus -9.5%). Leg and arm strength increased because of training intervention; all other variables were unchanged. None of these variables correlated with changes in SpAEE. CONCLUSION In boys who play ice hockey, spontaneous physical activity is inducible with resistance training; this effect seems to be independent of changes in body composition and strength. If this was confirmed in unselected children, resistance training might be a new strategy for childhood obesity prevention programs.

Strength Training and Physical Activity in Boys: a Randomized Trial

BACKGROUND: In developed societies levels of daily physical activity (PA) among school-age children are decreasing. This implies risk factors for cardiovascular and metabolic diseases. Specific strategies to improve levels of PA are needed. In prepubertal boys there is evidence that strength training increases spontaneous PA outside of training. METHODS: A total of 102 schoolchildren (age 10–14 years) in Switzerland were randomly assigned to physical education classes or to participate twice weekly at a guided strength training program for 19 weeks. Spontaneous PA energy expenditure (PAEE; 3axial accelerometry for 7 days), leg and arm strength, and body composition (dual energy radiograph absorptiometry) were measured at baseline, after 19 weeks of training intervention, and after 3 months of washout. RESULTS: There were no significant differences between the groups at baseline. In the intervention group, PAEE increased by 10% from baseline to end of training in boys (P = .02), but not in girls. Leg and arm strength were increased owing to training intervention in both boys and girls. All other variables were unchanged. Baseline PAEE was significantly negatively correlated with changes of PAEE. CONCLUSIONS: Targeted strength training significantly increases daily spontaneous PA behavior in boys. The less active children showed the greatest increase in spontaneous PAEE. Girls showed a similar increase in strength, but not in spontaneous PAEE. This may be explained by their earlier pubertal development. Strength training may be a promising strategy in schools to counteract decreasing levels of PA.

Association between Short Sleeping Hours and Physical Activity in Boys Playing Ice Hockey

OBJECTIVES To determine physical activity in healthy boys and how physical activity relates to training and daily awake hours. STUDY DESIGN In 66 boys (5 to 15 years) affiliated with an ice-hockey club, we measured total daily energy expenditure (TDEE, doubly-labeled water) and basal metabolic rate (ventilated-hood method). Physical activity energy expenditure for the whole day (DAEE), during training, and during spontaneous physical activity was measured by accelerometry and activity protocols. Univariate (UA) and multivariate (MA) correlation analysis was applied. RESULTS Physical activity level, DAEE, and TDEE for prepubertal (2.0 and 2.2 Mcal/d) and pubertal (bone age >or=13 years; 1.8 and 2.8 Mcal/d) boys were matched to literature data from normal boys of equal age. In prepubertal boys DAEE correlated positively with awake hours (r(UA) = 0.55, r(MA) = 0.39, P < .01). In pubertal boys this correlation was not significant, the slopes between the 2 groups being significantly different (P = .025). In prepubertal boys spontaneous physical activity expenditure correlated significantly positively with training activity expenditure (r(UA) = 0.72, r(MA) = 0.52, P < .001). CONCLUSION Contrary to findings in adults, where short sleepers had lower physical activity and intensive training was negatively compensated reducing spontaneous physical activity, in physically active prepubertal boys, total daily and spontaneous physical activity relate positively to awake hours and training; suggesting child-specific control of physical activity.

Parent preference in Switzerland for easy-to-use attributes of growth hormone injection devices quantified by willingness to pay

Sustained treatment adherence, usually over long periods of time, is critical to the success of growth hormone (GH) therapy. However, adherence rates are often poor which may result in suboptimal clinical outcomes. The type of device used by patients to administer their GH can influence adherence. Offering patients a choice of device maximizes the chance of adherence to treatment. Multiple factors will influence a patient’s choice of device, depending on individual priorities. This study evaluated the most preferred features of GH injection devices by parents using a web-based questionnaire and as assessed by their willingness to pay for specific device features. The results show that parents are willing to pay for device features facilitating ease of use.

Association between Foot Growth and Musculoskeletal Loading in Children with Prader-Willi Syndrome before and during Growth Hormone Treatment

OBJECTIVE To explore how foot growth relates to musculoskeletal loading in children with Prader-Willi syndrome (PWS). STUDY DESIGN In 37 children with PWS, foot length (FL) before and after 6 years of growth hormone therapy (GHT) was retrospectively evaluated with parental and siblings FL, height, and factors reflecting musculoskeletal loading, such as weight for height (WfH), lean body mass (LBM; dual energy X-ray absorptiometry, deuterium labeled water), physical activity (accellerometry), and walk age. Because of the typically biphasic evolution of body mass and the late walk age in PWS, 2 age groups were separated (group 1, >2.5 years; group 2, < or =2.5 years). RESULTS Children with PWS normalized height, but not FL after 6 years of GHT. Parental FL correlation with PWSs FL was lower than with siblings FL. In group 1, FL positively correlated with WfH, LBM, and physical activity. In group 2, FL negatively correlated with age at onset of independent ambulation. Foot catch-up growth with GHT was slower in group 2 compared with group 1. CONCLUSION In PWS, FL is positively associated with musculoskeletal loading. Small feet in children with PWS before and during long-term GHT may be more than just another dysmorphic feature, but may possibly reflect decreased musculoskeletal loading influencing foot growth and genetic and endocrine factors.

Foot Catch-Up Growth in Prader–Willi Syndrome: A Model for Foot Growth Regulation in Normal Children

This chapter proposes a new concept of foot growth regulation in addition to known endocrine and genetic factors. The Prader–Willi syndrome (PWS) is a genetically defined complex neurodevelopmental disorder characterized by short stature with small hands and feet, severe hypoactivity, progressive obesity, and endocrine disorders such as growth hormone deficiency. In PWS children as opposed to height, foot catch-up growth on growth hormone therapy is delayed and incomplete, contrasting to symmetric and complete catch-up growth observed in children with growth hormone deficiency, growth hormone insensitivity, and born small for gestational age. In hemiplegic and paraplegic children inactive legs are shorter than active legs. We therefore explored the hypothesis that in PWS children the relative reduction in foot length (FL) compared to height may be caused by reduced musculoskeletal loading reflecting severely reduced physical activity. In 37 PWS children we correlated foot length before and after 6 years of growth hormone therapy with parental and sibling’s FL, height and factors reflecting musculoskeletal loading such as weight for height (WfH), lean body mass (LBM), physical activity, and walk age. Because of the typically biphasic evolution of body mass and the late walk age in PWS, children were divided into age groups younger and older than 2.5 years. PWS children normalized height but not FL after 6 years of GHT. Parental FL correlation with PWS’s FL was lower than with sibling’s FL. In children older than 2.5 years FL positively correlated with WfH, LBM, and physical activity. In children younger than 2.5 years FL negatively correlated with age at onset of free walking. Foot catch-up growth on growth hormone therapy was slower in the younger compared to older children. We conclude that in PWS FL is positively associated with musculoskeletal loading. Small feet in PWS children before and during long-term growth hormone therapy may be more than just another dysmorphic feature, but possibly reflect decreased musculoskeletal loading influencing foot growth together with genetic and endocrine factors. Comparable to the “muscle-bone unit” explaining interdependency between bone remodeling and muscle strength, musculoskeletal loading impacts on foot growth, explaining about 25–50% of total variance of age-corrected FL. If our findings in PWS can be expanded to healthy children, the progressive reduction of physical activity observed over the last decades in healthy children may have consequences for FL of future generations.