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Exercise as it relates to Disease/Sedentary Behaviour, a metabolic risk?

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Sedentary Behaviour

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Sedentary behaviour can commonly be defined as when an individual is expending between 1 and 1.5 METS.[1] This can be any activity that involves limited energy expenditure such as lying down, sitting and driving. TV time, however, is still considered sedentary behaviour even though it is under reported in self-report studies.[2] American studies using accelerometers have shown that adults, aged 30–39, on average are sedentary for 7.2 hours per day,[3] while children aged 6–11 were less with 6 hours per day of sedentary time.[3] There are a variety of factors that influence this time, however, there has been an identified link between increased financial income and increased sitting time.[4]

Metabolic Risk

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Most commonly known as metabolic syndrome, it is a group of risk factors that contribute to increased heart disease and other heart problems.[5] The risk factors included in this vary from study to study, but the general guidelines are:

  • abdominal obesity[5]
  • atherogenic dyslipidemia[5]
  • raised blood pressure[5]
  • insulin resistance/glucose intolerance[5]
  • proinflammatory state[5]
  • prothrombotic state[5]

The research investigated looks into the association between these two factors amongst individuals without known diabetes.[6]

The Current Study

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Where was the research undertaken?

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The current study[6] was undertaken through the University of Queensland, Deakin University and the International Diabetes Institute for The Australian Diabetes, Obesity and Lifestyle Study (AUSDIAB). It was published in Diabetes Care, a peer reviewed journal.

What type of study was used?

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The current study[6] used a cross-sectional substudy to find appropriate participants, which best identifies prevalence in a certain population.[7] Participants undertook biochemical, anthropometric and behavioural assessments.[8] Uniaxial accelerometers were issued to these participants to measure their physical activity amounts.

What was involved in the research?

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The study involved 169 adults aged 30–87 (67 men and 102 women) who had been identified as having high sedentary times. This broad age range may decrease the accuracy of the study as older people generally have higher sedentary times compared to younger adults.

Before commencing the use of accelerometers, participants undertook the following assessments in accordance to the Australian Diabetes, Obesity and Lifestlye Study(AusDiab)[8] to assess their metabolic risk:

  • biochemical[8](HDL cholesterol, triglycerides, blood pressure, fasting plasma glucose, clustered metabolic risk score)
  • anthropometric[8](waist circumference)
  • behavioural[8]

Accelerometers were worn for 7 days to ensure a more realistic result was gained, rather than a one off study. The physical activity performed was broken down into 3 separate groups according to counts/minute measured from the accelerometers. These parameters for physical activity were derived from Freedsons cutoffs[9] for accelerometer-based activity, ensuring that a high standard was set to create reliable results. These were:

  • sedentary- <100 counts/min[9]
  • light intensity activity- 100-1951 counts/min[9]
  • moderate to vigorous activity- ≥1952[9]

Once data was collected, multiple linear regression analysis's were performed to identify whether there was any association between sedentary time and physical activity and metabolic risk.

Results

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Main Findings

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The results from the study found significant associations between all activity levels and waist circumference.[6] It was calculated that a 10% increase in sedentary time resulted in a 3.1 cm increase in waist circumference.

Major Findings

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  • All except light physical activity was associated with triglyceride levels
  • Independent associations between sedentary time, light activity, and mean activity intensity with waist circumference and clustered metabolic score
  • Majority of time spent sedentary (37%) or light activity (37%), only 4% spent at moderate to vigorous

The results support those of other studies, confirming the validity of the test[10] [11]

Discussion

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The researchers concluded that

  • sedentary time may have a greater influence on waist circumference than moderate-to-vigorous activity
  • there are metabolic benefits from substituting sedentary time with light physical activities
  • activities of daily living (ADLs) are proven to increase energy expenditure

Conclusions and implications

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  • the study confirmed the influence physical activity and sedentary time have on metabolic risk
  • it shows the influence various intensities have on different biochemical markers[6]
  • a down fall of the study was that it was a small population group. The study was relatively easy to administer and could be made much larger. Another was that the number of participants that did and did not complete the study was not revealed.
  • In general, the researchers used sound techniques to create a valid study that demonstrates the effect sedentary activity has on metabolic risk

Further reading

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Department of Health Sedentary time guidelines- http://www.health.gov.au/internet/main/publishing.nsf/Content/health-pubhlth-strateg-active-evidence.htm

Metabolic risk factors http://www.hormone.org/patient-guides/2008/metabolic-risk

References

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  1. ↑ Pate et al (2008). The evolving definition of “sedentary”. Exercise and Sport Science Reviews. Volume 36 Issue 4: 173-8
  2. ↑ Clark et al (2009). Validity and reliability of measures of television viewing time and other non-occupational sedentary behaviour of adults: a review. Obesity Reviews. Volume 10: 7-16.
  3. ↑ a b Matthews CE et al. Amount of time spent in sedentary behaviours in the United States, 2003-2004. American Journal of Epidemiology (25 February 2008). Volume 61 Issue 7: p875-81
  4. ↑ Australian Bureau of Statistics. Australian Health Survey: Physical Activity, 2011-2012.
  5. ↑ a b c d e f g Third report of the National Cholesterol Education Program (NCEP) expert panel on detection, evaluation, and treatment of high blood cholesterol in adults. Adult Treatment Panel III. Final report. Circulation. 2002; Volume 106: 3143–3421
  6. ↑ a b c d e Objectively measured sedentary time, Physical Activity and Metabolic Risk. Diabetes Care. Feburary 2008. Issue 31, Volume 2. P369-371
  7. ↑ Study Design III: Cross Sectional Studies. Evidence Based Dentistry. 2006. Volume 7. P24-25.
  8. ↑ a b c d e Dunstan DW, Zimmet PZ, Welborn TA, Cameron AJ, Shaw J, de Courten M, Jolley D, McCarty DJ. The Australian Diabetes, Obesity and Lifestyle Study (AusDiab). Methods and response rates. Diabetes Res Clin Pract. 2002 Volume 57. P119–129
  9. ↑ a b c d Freedson PS, Melanson E, Sirard J. Calibration of the Computer Science and Applications, Inc. accelerometer. Med Sci Sports Exerc. 1998. Volume 30. P777–781
  10. ↑ Healy GN et al. Television time and continuous metabolic risk in physically active adults. Med. Sci. Sports Exerc. 2008. Volume 40. Issue 4. P639-645.
  11. ↑ Healy GN et al. Sedentary time and cardio-metabolic biomarkers in US adults: NHANES 2003-2006. European Heart Journal. March 2011. Volume 32. Issue 5. P590-597.
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