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Muscle function and physical activity in pre-pubertal school children

Stenevi Lundgren, Susanna LU (2011) In Lund University, Faculty of Medicine Doctorial Dissertation Series 2011:32.
Abstract (Swedish)
Popular Abstract in Swedish

Bakgrund: Regelbunden fysisk aktivitet och träning anses som en livsstilsfaktor som kan förbättra muskelstyrkan, skelettet, konditionen och kroppssammansättningen. För barn och ungdomar är fysisk aktivitet inte bara viktigt för att träna de muskulära funktionerna, koordinationen och balansen. I ett större perspektiv kan en fysiskt aktiv livsstil också minska risken för hjärt- och kärlsjukdomar, fetma, benskörhet och en rad andra sjukdomar i samhället. Tidigare undersökningar har studerat effekterna av medelintensiv fysisk aktivitet beträffande kondition, fetma och skelettets hållfasthet. Tiden innan och under tidig pubertet anses då allmänt som det bästa tillfället att förbättra skelettets... (More)
Popular Abstract in Swedish

Bakgrund: Regelbunden fysisk aktivitet och träning anses som en livsstilsfaktor som kan förbättra muskelstyrkan, skelettet, konditionen och kroppssammansättningen. För barn och ungdomar är fysisk aktivitet inte bara viktigt för att träna de muskulära funktionerna, koordinationen och balansen. I ett större perspektiv kan en fysiskt aktiv livsstil också minska risken för hjärt- och kärlsjukdomar, fetma, benskörhet och en rad andra sjukdomar i samhället. Tidigare undersökningar har studerat effekterna av medelintensiv fysisk aktivitet beträffande kondition, fetma och skelettets hållfasthet. Tiden innan och under tidig pubertet anses då allmänt som det bästa tillfället att förbättra skelettets hållfasthet. Om detta även gäller för muskelfunktionen är mindre utrett. Styrketräning hos barn har t.ex. visat sig ge positiva resultat på muskelstyrka men om motsvarande effekt kan uppnås av ett medelintensivt träningsprogram är oklart. Innan man rekommenderar fysisk aktivitet generellt i samhället för att förebygga svag muskelstyrka bör man därför visa att även allmänna träningsprogram, på en nivå så att alla barn klarar att delta, har effekt. Skolan har då ansetts vara den ideala, och möjligen den enda arenan, där alla barn kan nås. Mot denna bakgrundskunskap har denna avhandling utformats för att dels presentera normalvärden för muskelstyrka och mjukdelsvävnad hos barn före puberteten, och dels utvärdera om ett medelintensivt interventionsprogram i form av utökad skolgymnastik påverkar utvecklingen av muskelfunktionen hos barn. Avhandlingen undersöker även om det är gynnsammare för muskelutvecklingen att gå eller cykla till skolan jämfört med om man åker bil eller buss.

Material och metoder: Försökspersonerna som medverkade i denna avhandling hämtades från den så kallade Bunkeflostudien, eller på engelska, the Pediatric Osteoporosis Prevention (POP) Study. I denna studie genomfördes ett s.k. interventionsprogram. En grupp barn (68 pojkar och 53 flickor) deltog i träningsgruppen som fick utökad fysisk aktivitet i form av 40 minuters daglig skolgymnastik, d.v.s. 200 minuter per vecka. Dessa jämfördes med en kontrollgrupp, som bestod av 46 pojkar och 50 flickor, som erhöll 60 minuter skolgymnastik per vecka. För att utvärdera effekten av träningen jämfördes förändringen i muskelstyrka, hopphöjd och kroppssammansättning mellan de två grupperna under det året som studien pågick. Den fysiska aktivitetsnivån utvärderades med ett frågeformulär. För att utvärdera hur skoltransport påverkar utvecklingen av muskelfunktionen delades barnen in i två grupper baserade på hur de hade valt att ta sig till skolan under ett år; en grupp som gick eller cyklade och en grupp som åkte bil eller buss. Fysisk aktivitetsnivå uppskattades dels med ett frågeformulär och dels med en mätare som barnen bar under fyra dagar, en s.k. accelerometer. På så sätt erhölls ett objektivt mått på hur mycket barnet rört sig under de fyra dagarna.

För att kunna redovisa normala värden för muskelstyrka, hopphöjd och kroppssammansättning i åldrarna 6 till 12 år inkluderades ett större antal barn som alla mättes innan man startade den ökade skolgymnastiken. I denna grupp ingick 246 pojkar och 190 flickor där de flesta barnen var förpubertala men där ett fåtal hade nått tidig pubertet. Mätningarna i samtliga delarbeten utgjordes av tester av muskelstyrka i knäets sträckar- och böjarmuskulatur samt hopphöjd. Dessutom mättes kroppssammansättning med lågdosröntgen, dels mängden ”lean body mass”, som i huvudsak består av muskulatur, och dels mängden fett. Vikt och längd mättes med standardutrustning.

Resultat: Både pojkar och flickor med daglig skolgymnastik hade större ökning av de olika muskelvariablerna under ett år. Däremot påverkades inte hopphöjden av den ökade skolgymnastiken. Det verkar inte heller som om vare sig pojkar eller flickor som gick eller cyklade till skolan erhöll en mer gynnsam utveckling av muskelfunktionen jämfört med de barn som åkte bil eller buss. Samtliga barn i studien hade höga fysiska aktivitetsnivåer. Normalvärdena för muskelstyrka, hopphöjd och kroppssammansättning hos barn i åldrarna 6 till 12 år visade att samtliga variabler ökar med ökande ålder utan att man fram till puberteten kunde se några skillnader mellan pojkar och flickor.

Slutsats: Fram till puberteten ökar muskelstyrka närmast linjärt hos både pojkar och flickor utan att man ser några könsskillnader. Daglig skolgymnastik före puberteten kan vara en metod att öka muskelstyrka hos båda könen, i all fall i ett kortare tidsperspektiv. Dessa fynd antyder att utökad skolgymnastik hos förpubertala barn kan vara en möjlig angreppspunkt för att förbättra muskelfunktionen. Däremot verkar inte valet av transportmedel till skolan påverka utvecklingen av muskelfunktionen i dessa åldrar. (Less)
Abstract
Background: Regular participation in physical activity or organized exercise is regarded as one important lifestyle factor that could improve musculoskeletal health, fitness and body composition. For children and adolescents physical activity is important not only in training of the neuromuscular system, coordination and balance, but in a wider perspective, for adopting a lifestyle that possibly reduces the risk of coronary artery disease, obesity, osteoporosis and other contributors to morbidity and mortality in the population. Previous studies have investigated the effects of moderate physical activity on fitness, obesity and bone health. The pre- and early pubertal period is usually considered as the best opportunity to enhance skeletal... (More)
Background: Regular participation in physical activity or organized exercise is regarded as one important lifestyle factor that could improve musculoskeletal health, fitness and body composition. For children and adolescents physical activity is important not only in training of the neuromuscular system, coordination and balance, but in a wider perspective, for adopting a lifestyle that possibly reduces the risk of coronary artery disease, obesity, osteoporosis and other contributors to morbidity and mortality in the population. Previous studies have investigated the effects of moderate physical activity on fitness, obesity and bone health. The pre- and early pubertal period is usually considered as the best opportunity to enhance skeletal strength, but whether the same applies to neuromuscular function has seen less evaluation. In addition, muscular strength in pre-pubertal children has been shown to benefit from resistance training but whether similar benefits can be achieved by a moderately intense exercise programme is unclear. Hence, before we can recommend physical activity as prevention against low muscle strength and impaired neuromuscular function, we ought to show effects of intervention programmes on a population-based level with moderately intense exercise so that virtually all children can participate. School has been regarded as the ideal and perhaps only arena that could include all children within a defined population. This is the reason why this thesis was designed to present normative data for muscle strength and soft tissues in pre-pubertal children, and also to evaluate whether a general school curriculum-based moderately intense physical education intervention programme and mode of transportation to school could influence the development of neuromuscular function.

Materials and Methods: The participants in this thesis were collected from the Pediatric Osteoporosis Prevention (POP) cohort. A school-curriculum-based exercise intervention programme comprising 40 minutes of physical education per school day was initiated and 68 boys and 53 girls aged 6 to 8 from one school were included in the intervention group. Age- and gender-matched children in the control group (46 boys and 50 girls) from three neighbouring schools were assigned to the general Swedish school curriculum of 60 minutes of physical education per week. When evaluating the effect of the mode of school transportation, comparisons were made between children who reported to have walked or cycled to school, and those who had commuted by bus or car. Physical activity was measured objectively by accelerometers worn for four consecutive days. Accelerometer measurements, however, were not done until two years after study start. In the cross-sectional normative data report (paper IV) 246 boys and 190 girls aged 6 to 12 in Tanner stages I and II were included.

Measurements were conducted before any intervention was initiated. Neuromuscular function was assessed by concentric isokinetic peak torque of the knee extensors and flexors at 60° and 180°/s and with vertical jump height test. Total body soft tissue composition was evaluated by dual energy X-ray absorptiometry and body mass and stature by standard measurements. Level of physical activity was subjectively estimated through questionnaires. In the prospective part of the study (papers I, II and III), neuromuscular and soft tissue development was followed for one year in the intervention group and control group.

Results: The normative evaluation reported improved performance and higher values in all anthropometric measurements with advancing ages, and with no constant gender differences across the age groups. Both boys and girls with increased school-based physical educational classes had higher annual gains in different muscle strength indices, but not in vertical jump height, than the control group. Walking or cycling to school was not associated with beneficial gain in muscle strength indices or vertical jump height in either boys or girls. The level of physical activity measured by accelerometers was so high in these children that all reached the level recommended by the United Kingdom Expert Consensus Group of 60 minutes of moderate-to-vigorous daily physical activity.

Conclusion: Normative gender-specific data on muscle strength, lean and fat mass and vertical jump height show that in Swedish children aged 6 to 12 in Tanner stage I and II there seems to be an increase with age and no structural gender differences. Daily physical education classes in school could be used in pre-pubertal boys and girls as a strategy to increase muscle strength, at least in the short term. These findings suggest increased physical education in pre-pubertal children as one possible strategy to improve neuromuscular function on a population level in society. In contrast, the mode of school transportation seems not to influence the measured traits, at least not in young children with a generally high level of everyday physical activity. (Less)
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author
supervisor
opponent
  • Docent Thomeé, Roland, Avdelningen för ortopedi, Sahlgrenska Universitetssjukhuset, Göteborg
organization
publishing date
type
Thesis
publication status
published
subject
keywords
children, physical activity, exercise, isokinetic muscle strength, vertical jump height, normative, intervention, school transport, DXA, anthropometry, fat mass, lean mass, weight, height, body mass index, girls, boys, pre-pubertal
in
Lund University, Faculty of Medicine Doctorial Dissertation Series
volume
2011:32
pages
134 pages
publisher
Lund University
defense location
Föreläsningssalen, plan 5 Ing 25b, Ortopediska kliniken SUS, Malmö
defense date
2011-04-28 09:00
ISSN
1652-8220
ISBN
978-91-86671-80-8
language
English
LU publication?
yes
id
76686ae0-7824-40f9-a5e3-ddcb199fbaf2 (old id 1886882)
date added to LUP
2011-04-06 09:40:15
date last changed
2016-09-19 08:44:46
@phdthesis{76686ae0-7824-40f9-a5e3-ddcb199fbaf2,
  abstract     = {Background: Regular participation in physical activity or organized exercise is regarded as one important lifestyle factor that could improve musculoskeletal health, fitness and body composition. For children and adolescents physical activity is important not only in training of the neuromuscular system, coordination and balance, but in a wider perspective, for adopting a lifestyle that possibly reduces the risk of coronary artery disease, obesity, osteoporosis and other contributors to morbidity and mortality in the population. Previous studies have investigated the effects of moderate physical activity on fitness, obesity and bone health. The pre- and early pubertal period is usually considered as the best opportunity to enhance skeletal strength, but whether the same applies to neuromuscular function has seen less evaluation. In addition, muscular strength in pre-pubertal children has been shown to benefit from resistance training but whether similar benefits can be achieved by a moderately intense exercise programme is unclear. Hence, before we can recommend physical activity as prevention against low muscle strength and impaired neuromuscular function, we ought to show effects of intervention programmes on a population-based level with moderately intense exercise so that virtually all children can participate. School has been regarded as the ideal and perhaps only arena that could include all children within a defined population. This is the reason why this thesis was designed to present normative data for muscle strength and soft tissues in pre-pubertal children, and also to evaluate whether a general school curriculum-based moderately intense physical education intervention programme and mode of transportation to school could influence the development of neuromuscular function.<br/><br>
Materials and Methods: The participants in this thesis were collected from the Pediatric Osteoporosis Prevention (POP) cohort. A school-curriculum-based exercise intervention programme comprising 40 minutes of physical education per school day was initiated and 68 boys and 53 girls aged 6 to 8 from one school were included in the intervention group. Age- and gender-matched children in the control group (46 boys and 50 girls) from three neighbouring schools were assigned to the general Swedish school curriculum of 60 minutes of physical education per week. When evaluating the effect of the mode of school transportation, comparisons were made between children who reported to have walked or cycled to school, and those who had commuted by bus or car. Physical activity was measured objectively by accelerometers worn for four consecutive days. Accelerometer measurements, however, were not done until two years after study start. In the cross-sectional normative data report (paper IV) 246 boys and 190 girls aged 6 to 12 in Tanner stages I and II were included.<br/><br>
Measurements were conducted before any intervention was initiated. Neuromuscular function was assessed by concentric isokinetic peak torque of the knee extensors and flexors at 60° and 180°/s and with vertical jump height test. Total body soft tissue composition was evaluated by dual energy X-ray absorptiometry and body mass and stature by standard measurements. Level of physical activity was subjectively estimated through questionnaires. In the prospective part of the study (papers I, II and III), neuromuscular and soft tissue development was followed for one year in the intervention group and control group. <br/><br>
Results: The normative evaluation reported improved performance and higher values in all anthropometric measurements with advancing ages, and with no constant gender differences across the age groups. Both boys and girls with increased school-based physical educational classes had higher annual gains in different muscle strength indices, but not in vertical jump height, than the control group. Walking or cycling to school was not associated with beneficial gain in muscle strength indices or vertical jump height in either boys or girls. The level of physical activity measured by accelerometers was so high in these children that all reached the level recommended by the United Kingdom Expert Consensus Group of 60 minutes of moderate-to-vigorous daily physical activity. <br/><br>
Conclusion: Normative gender-specific data on muscle strength, lean and fat mass and vertical jump height show that in Swedish children aged 6 to 12 in Tanner stage I and II there seems to be an increase with age and no structural gender differences. Daily physical education classes in school could be used in pre-pubertal boys and girls as a strategy to increase muscle strength, at least in the short term. These findings suggest increased physical education in pre-pubertal children as one possible strategy to improve neuromuscular function on a population level in society. In contrast, the mode of school transportation seems not to influence the measured traits, at least not in young children with a generally high level of everyday physical activity.},
  author       = {Stenevi Lundgren, Susanna},
  isbn         = {978-91-86671-80-8},
  issn         = {1652-8220},
  keyword      = {children,physical activity,exercise,isokinetic muscle strength,vertical jump height,normative,intervention,school transport,DXA,anthropometry,fat mass,lean mass,weight,height,body mass index,girls,boys,pre-pubertal},
  language     = {eng},
  pages        = {134},
  publisher    = {Lund University},
  school       = {Lund University},
  series       = {Lund University, Faculty of Medicine Doctorial Dissertation Series},
  title        = {Muscle function and physical activity in pre-pubertal school children},
  volume       = {2011:32},
  year         = {2011},
}