Bone mineral parameters in 11–13-year-old boys: associations with body composition and physical activity
Date
2014-05-27
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Abstract
Puberteediperioodi jooksul toimuvad inimese organismis mitmed hormonaalsed, morfoloogilised ja antropomeetrilised (kasvuspurt) muutused. Erinevad uuringud on leidnud, et nii positiivsed kui ka negatiivsed muutused, mis tekivad puberteedi perioodi jooksul omavad suurt mõju inimese edasisele elukäigule.
Puberteediperioodi jooksul toimub ka väga intensiivne luukoe juurdekasv. Uuringutes on leitud, et umbes 40-50% luumassi juurdekasvust toimub just puberteediperioodil, saavutades tippmassi umbes 20-22 eluaastal, millest edasi algab luumassi vähenemine. Osteoporoos ehk luude hõrenemine on seisund, mille puhul on luumineraalide hulk vähenenud ning luud muutuvad hapraks ja suureneb luumurruoht. Seega, mida kõrgem on luumineraalide sisaldus, seda hiljem tinglikult avaldub osteoporoosi oht, millest järeldub, et puberteediea jooksul, mil luukude on kõige paremini mõjustatav tuleb luumineraalide suurenemisele pöörata olulist tähelepanu.
Uuringud on samuti näidanud, et luumineraalide hulga suurenemine (luutiheduse kasv) on väga tihedas seoses mehaanilise koormusega, mis avaldub luudele. Üheks selliseks faktoriks on inimese kehamassi suurus. On leitud, et suurema kehamassiga inimestel on suurem luutihedus võrreldes väiksema kehamassiga inimestega. Siiski esineb ka vasturääkivusi, millist mõju avaldab inimese keha rasvamass suurus võrreldes keha rasvavaba massi (kaasaarvatud keha lihasmassi) osakaaluga.
Samuti on leitud, et kehaline aktiivsus, eriti just tugev, löögilise iseloomuga kehaline aktiivsus omab positiivset seost luutiheduse suurenemisega. Samas ei ole teada, milline on selles mudelis keha koostise erinevate komponentide osakaal just erineva suurusega kehamassiga inimestel. Siiamaani tehtud uuringud on põhiliselt olnud ristläbilõikeuuringud, samas kui on teada, et just puberteediea jooksul toimub oluline kehalise aktiivsuse vähenemine. Seetõttu ei pruugi ristläbilõike uuringute tulemused anda usaldusväärset infot kehalise aktiivsuse muutuse kohta.
Käesoleva uurimistöö eesmärgiks oli uurida võimalikke seoseid keha koostise parameetrite, kehalise aktiivsuse ning luu parameetrite vahel puberteediealistel poistel.
Vastavalt uurimistöö eesmärgile püstitati järgmised konkreetsed ülesanded:
1) uurida erinevaid luutiheduse parameetreid ülekaalulistel ja normaalkaalulistel poistel;
2) uurida keha koostise ja keha erinevate luutiheduse näitajate vahelisi seoseid ülekaaluslistel ja normaalkaalulistel poistel;
3) uurida seoseid keha koostise ja erineva intensiivsusega kehalise aktiivsuse ning luutiheduse parameetrite vahel ülekaaluslistel ja normaalkaalulistel poistel;
4) uurida longituudselt erinevate kehalise aktiivsuse näitajate muutuste mõju luutiheduse näitajate arengule ülekaalulistel ja normaalkaalulistel poistel.
Antud uuringus osales 264 10-13 aasta vanust Tartu ja selle ümbruskonna koolide poissi. Vaatlusalused jaotati normaal- ja ülekaalulisteks kasutades McCarthy jt. (2006) metoodikat. Vaatlusalustel määrati keha koostis DXA meetodil, kehaline aktiivsus aktseleromeetri abil, bioloogiline vanus, kasutades röntgenülesvõtet labakäest. Sarnased testid viidi läbi ühe aasta pärast. Longitudinaalsesse analüüsi kaasati ainult need vaatlusalused, kellel olid olemas kõik andmed nii esimesest kui ka teisest mõõtmispunktist.
Käesoleva uuringu põhjal tehti järgmised järeldused:
1) Ülekaaluliste poiste luutiheduse näitajad olid oluliselt kõrgemad võrreldes normaalkaaluliste poiste vastavate näitajatega. Samas ei leitud usutavaid erinevusi selja lumbaarosa ja reieluukaela mahulises luutiheduse näitajas, kuid ülekaalulistel esines oluliselt madalam kogu keha mahuline luutihedus.
2) Keha rasvavaba mass (ja rasvavaba massi indeks) kajastavad paremini luutiheduse näitajaid normaalkaalulistel poistel, ülekaalulistel poistel kajastavad luutiheduse parameetreid paremini keha rasvamass (ja rasvamassi indeks).
3) Kehaline aktiivsus omab suuremat mõju luutiheduse parameetritele ülekaalulistel poistel ning lisaks intensiivsele kehalisele aktiivsusele omab olulist mõju ka mõõdukas kehaline aktiivsus.
4) Kehalise inaktiivsuse suurenemine omab olulist negatiivset mõju määratud luuparameetrite arengule ühe aastase uuringuperioodi jooksul 11-13 aastastel poistel.
Kokkuvõttes näitasid antud uuringu tulemused, et erinevate keha koostise ja kehalise aktiivsuse näitajate mõju luuparameetrite arengule on puberteediperioodi jooksul erinev normal- ja ülekaaluliste poiste vahel.
Puberty is one of the most dynamic periods of growth and development, and is characterized by rapid changes in body morphology and composition. Different studies have found that both positive and negative changes take place, which might have significant impact for the future life. Pubertal years are also an important period for linear growth and bone mineral accrual. Bone mineralization increases with age, height, and body mass throughout childhood, with a most significant gain during pubertal development. Studies have indicated that approximately 40-50% increase in bone mass take place during the puberty, reaching the highest bone mass at approximately 20-22 years of age from where ongoing the bone mass starts to decrease. Osteoporosis can be characterized as a state with decreased bone mineral content that may result in fractures. Therefore, the higher is the achieved bone mass, the later the osteoporosis will probably occur. This indicates the high importance of the puberty period where the bone mineral parameters can be modified on great extent. It has been shown that the increase in bone mineral parameters is highly related to mechanical loading to bones. One of these factors is the size of the body, with subjects who have higher body mass have also higher bone mineral density. In contrast, it has been argued that the main factor regarding bone mineral accrual is not the body mass per se, but the amount of lean body mass. Further, it has been found that physical activity, especially high impact physical activity has a positive influence on bone mineral parameters. However, it is not known what is the contribution of body composition in subjects with different physical activity levels. So far the majority of the studies have been mainly cross-sectional, while it is known that during puberty physical activity decreases significantly. Therefore, cross-sectional design might not be very reliable in describing the changes that occur in physical activity during puberty. The general aim of the present study was to evaluate bone mineral parameters in normal and overweight boys aged 11-13 years in associations with body composition and physical activity. According to the general aim, the specific aims of the present investigation were to: 1) investigate different bone mineral density values between overweight and normal weight boys (Study I); 2) investigate the relationships of different body composition parameters on whole body and areal bone mineral density values in overweight and normal weight boys (Study I); 3) investigate the relationships of different physical activity levels on whole body and areal bone mineral density values in overweight and normal weight boys (Study II); 4) investigate the physical activity changes to whole body and areal bone mineral accrual during one year period in 11-13-year-old boys (Study III). 264 boys, aged 11-13 years from Tartu and its surroundigs took part in this investigation. They were divided into normal and overweight categories according to cut-off points by McCarthy et al (2006). Their body composition was measured using DXA methodology, physical activity was measured by 7-day accelerometry and biological age by X-ray of the wrist. Similar testing was conducted in one-year period. Only those subjects were included into analysis who had accumulated all data from both measurements. In conclusion: 1) Overweight boys, aged 11-13 years had higher whole body, lumbar spine and femoral neck BMC values compared with normal weight boys. In contrast, no differences in lumbar spine and femoral neck body apparent (volumetric) BMD were seen in both groups. Despite higher whole body BMD, overweight boys had lower whole body apparent (volumetric) BMD compared with normal weight boys; 2) Fat free mass characterizes better than fat mass and BMI bone mineral values in normal weight boys, while fat mass and BMI are better determinants of bone mineral values in overweight boys; 3) Physical activity is more associated with bone mineral values in overweight boys compared with normal weight boys, and in addition to vigorous physical activity, already moderate physical activity has the significant impact on bone mineral values in overweight boys; 4) The increase in sedentary time emerged as one of the main predictors from physical activity to have the negative influence on bone mineral acquisition during a one-year observation period in 11-13-year-old boys.
Puberty is one of the most dynamic periods of growth and development, and is characterized by rapid changes in body morphology and composition. Different studies have found that both positive and negative changes take place, which might have significant impact for the future life. Pubertal years are also an important period for linear growth and bone mineral accrual. Bone mineralization increases with age, height, and body mass throughout childhood, with a most significant gain during pubertal development. Studies have indicated that approximately 40-50% increase in bone mass take place during the puberty, reaching the highest bone mass at approximately 20-22 years of age from where ongoing the bone mass starts to decrease. Osteoporosis can be characterized as a state with decreased bone mineral content that may result in fractures. Therefore, the higher is the achieved bone mass, the later the osteoporosis will probably occur. This indicates the high importance of the puberty period where the bone mineral parameters can be modified on great extent. It has been shown that the increase in bone mineral parameters is highly related to mechanical loading to bones. One of these factors is the size of the body, with subjects who have higher body mass have also higher bone mineral density. In contrast, it has been argued that the main factor regarding bone mineral accrual is not the body mass per se, but the amount of lean body mass. Further, it has been found that physical activity, especially high impact physical activity has a positive influence on bone mineral parameters. However, it is not known what is the contribution of body composition in subjects with different physical activity levels. So far the majority of the studies have been mainly cross-sectional, while it is known that during puberty physical activity decreases significantly. Therefore, cross-sectional design might not be very reliable in describing the changes that occur in physical activity during puberty. The general aim of the present study was to evaluate bone mineral parameters in normal and overweight boys aged 11-13 years in associations with body composition and physical activity. According to the general aim, the specific aims of the present investigation were to: 1) investigate different bone mineral density values between overweight and normal weight boys (Study I); 2) investigate the relationships of different body composition parameters on whole body and areal bone mineral density values in overweight and normal weight boys (Study I); 3) investigate the relationships of different physical activity levels on whole body and areal bone mineral density values in overweight and normal weight boys (Study II); 4) investigate the physical activity changes to whole body and areal bone mineral accrual during one year period in 11-13-year-old boys (Study III). 264 boys, aged 11-13 years from Tartu and its surroundigs took part in this investigation. They were divided into normal and overweight categories according to cut-off points by McCarthy et al (2006). Their body composition was measured using DXA methodology, physical activity was measured by 7-day accelerometry and biological age by X-ray of the wrist. Similar testing was conducted in one-year period. Only those subjects were included into analysis who had accumulated all data from both measurements. In conclusion: 1) Overweight boys, aged 11-13 years had higher whole body, lumbar spine and femoral neck BMC values compared with normal weight boys. In contrast, no differences in lumbar spine and femoral neck body apparent (volumetric) BMD were seen in both groups. Despite higher whole body BMD, overweight boys had lower whole body apparent (volumetric) BMD compared with normal weight boys; 2) Fat free mass characterizes better than fat mass and BMI bone mineral values in normal weight boys, while fat mass and BMI are better determinants of bone mineral values in overweight boys; 3) Physical activity is more associated with bone mineral values in overweight boys compared with normal weight boys, and in addition to vigorous physical activity, already moderate physical activity has the significant impact on bone mineral values in overweight boys; 4) The increase in sedentary time emerged as one of the main predictors from physical activity to have the negative influence on bone mineral acquisition during a one-year observation period in 11-13-year-old boys.
Description
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Keywords
luutihedus, keha koostis, füüsiline aktiivsus, poisid, bone density, body composition, physical activity, boys