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The effect of structured and lifestyle physical activity interventions on the bone health and body composition of 9-11 year old children

Mcwhannell, N J (2009) The effect of structured and lifestyle physical activity interventions on the bone health and body composition of 9-11 year old children. Doctoral thesis, Liverpool John Moores University.

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Childhood obesity is becoming increasingly prevalent in the UK and globally. Over the last 10 years, there has been a rise in prevalence of risk factors for health and a decline in physical activity. Obesity is major health risk factor for a number of other chronic diseases, some of which are prevalent in children. Regular physical activity is associated with reduced adiposity, healthier metabolic status lower risk factors of diabetes and CHD and enhanced bone mineral accrual and protection against osteoporosis. Recent literature suggests that children may not be meeting the recommended daily guideline for physical activity of 60 min per day (Riddoch et al., 2007), while others suggest this guideline is insufficient to protect against risk factors in children. Assessment of programmes promoting physical activity, with robust health related outcome measures are therefore warranted Initially, sixty-one children were recruited for a 9-week exploratory trial. The trial assessed the effect of a structured high impact exercise (STEX) and a lifestyle intervention (PASS). Changes in dual-energy X-ray absorptiometry (DXA) derived body composition and bone mineral were compared to age matched controls (CaNT). The STEX intervention resulted in an additional mean increase in total body BMC of 63.3 g (P= 0.019) and an additional increase of 0.011 g.cm-2 (P= 0.018) for BMD over changes observed in controls. Neither intervention stimulated significant increases in BMC or BMD at the femoral neck or lumbar spine (P> 0.05) compared with the controls. No significant changes were found in fat mass index (P> 0.05), lean mass index (P> 0.05) or percent body fat (p = 0.09) in any groups. Structured impact exercise promoted significant and clinically relevant increases in bone measures, without significant changes to body composition. The exploratory finding therefore supported the need for a larger, definitive randomised trial to confirm the results. Following this, a large cohort of Liverpool school children (n=152) was recruited for cross-sectional analysis. Measures included 3-day physical activity using a uniaxial accelerometer, maturity status, cardia-respiratory fitness and skin-fold measurements in addition to body composition, bone mineral content and density. Analysis of variance was used to uncover any sex differences, partial correlation analysis was performed to investigate relationships between health-related variables and physical activity, with maturity offset as the controlling variable. Regression analysis was performed to find the best predictor of BMC and BMD (primary outcome variable), using LM, FM, Mass, and maturity offset as predictor variables. The results showed that children participated in the recommended amount of activity. However, body fat measures indicated that the children fell between the 85th-95% percentile for overweight. Further more BMD status of both sexes also fell below reference values. The dose-response relationship was highlighted as children who participated in <60 mln.oay" recommendation were less physically fit (P=0.001) and fatter (P<0.001) than children achieving this guideline. Children participating in over >90 min.day" had significantly lower percent body fat (P=0.005) and fat mass (P=0.04) than children who participated in <60 min.day" and significantly lower percent body fat (P=0.02)than all children who participated in <90 min.day". The findings highlight the importance of the high volume (>90 rnin.day") and high-intensity physical activity (over 10 min.day") as a precursor to low body fat and high bone mineral in children. The one hundred and fifty-two children from the baseline cohort were allocated to 1 of 4 groups over a 12 month period. Three groups received a different physical activity intervention; a high-intensity programme ('HIPA'), a skill development programme ('FMS') or a lifestyle-based programme ('PASS'). The 'HIPA' and 'FMS' groups participated in an after-school club (2x60 min.week"), the 'PASS' group attended weekly classroom sessions (1 x week) delivered by a lifestyle coach during the school day. The control group ('CaNT') received health information. All baseline measures were repeated at 9 and 12 months (during and after) intervention. All interventions minimised fat mass accumulation, with the 'HIPA' intervention being most effective (P=0.03), implying that the high-intensity nature of the activity sessions was more effective at minimising body fat accumulation. The greatest magnitude of change in femoral neck BMC (P<0.001) and BMD (P<0.001) and cardiorespiratory fitness (P=0.023) was also reported by the 'HIPA' group which is likely to be attributable to the intensity of the weight-bearing activities included in the 'HIPA' programme. The findings suggested that the 'HIPA' intervention was most beneficial for health outcomes, but all interventions had significant effect on increasing time spent in physical activity. The studies within this thesis have provided a unique insight in to the current bone health status, body composition and physical activity of 9-11 year old Liverpool school children. Further data were also generated on the effect of different physical activity interventions on bone health, body composition and physical activity. The findings from this thesis conclude that a proportion of 9- 11 year old children were overweight despite meeting physical activity recommendations of 60 min.day". The high-intensity physical activity intervention had the most beneficial impact on bone health, body composition and cardio-respiratory fitness when compared to the controls. The quantity of physical activity and the time spent in high intensity activity warrants further investigation to quantify an optimal dose.

Item Type: Thesis (Doctoral)
Subjects: G Geography. Anthropology. Recreation > GV Recreation Leisure
R Medicine > RC Internal medicine > RC1200 Sports Medicine
R Medicine > RJ Pediatrics > RJ101 Child Health. Child health services
Divisions: Sport & Exercise Sciences
Date Deposited: 15 Mar 2017 11:16
Last Modified: 03 Sep 2021 23:30
DOI or ID number: 10.24377/LJMU.t.00005953
URI: https://researchonline.ljmu.ac.uk/id/eprint/5953
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