Exercise as it relates to Disease/Decline in physical activity among biracial adolescent girls

This is an analysis of the journal article “Decline in Physical Activity in Black Girls and White Girls During Adolescence” by Kimm et al, published in the New England Journal of Medicine (2002).

What is the background to this research?
Physical activity is defined by the World Health Organisation (WHO) as being “any bodily movement produced by skeletal muscles that requires energy expenditure…” and it is an essential component for a healthy life as it prevents against chronic diseases and obesity,. Evidence suggests that physical inactivity accounts for 6% of coronary heart disease, 7% of type II diabetes, and 10% of breast cancer and colon cancer diagnoses. It is also said to be the cause of 9% of premature deaths and caused 5.8 million of the 57 million deaths in 2008. With much of the population living an inactive lifestyle it presents a major public health concern.

If physical inactivity were to be reduced by 10%, more than 533, 000 deaths could be adverted each year, and being a highly modifiable factor, efforts should be made on educating society to live a physically active lifestyle from a young age. Lifestyle factors such as sedentary forms of employment and transport, as well as the introduction to technology can be noted as influences for the high prevalence of physical inactivity.

The decrease of physical activity in adolescent girls is particularly worrying as the sharpest decline is noticed between the ages of 9-19 as shown in the study by Kimm et al, and is the age where future habits are typically made.

Where is the research from?
Kimm et al, conducted this research as part of The National Heart, Lung, and Blood Institute Growth and Health Study where participants were recruited from schools in the San Francisco area, Cincinnati, and also from a health maintenance organization located in Washington D.C.

What kind of research was this?
The research was conducted as a multicentre prospective cohort study involving the use of the Habitual Activity Questionnaire (HAQ) to collect the required information. This is a different approach compared to other studies that used accelerometers to measure physical activity levels in adolescent girls,. However, the use of the HAQ was convenient considering the length of the study.

What did the research involve?
A total of 1213 black girls and 1166 white girls were studied over a 10-year period, with the first year of the study beginning when the girls were 9–10 years old, and completing when the girls were 18–19 years old. The overall follow up rate was 89% by the completion of the study, consisting of 91% of the black girls and 88% of the white girls that initially began the study. The cohort were required to complete the questionnaire in the years 1, 3, 5, 7, 8, 9, and 10 of the study which was used to identify the amount of physical activity each subject completed per week other than physical education classes undertaken as part of the school curriculum. Therefore, the questionnaires were used to collect information on the leisure-time physical activity of each participant that required the use of more energy than those activities of daily living. Two sample T tests, X2 tests, or Wilcox two-sample tests were used in order to examine the effects of racial differences in descriptive differences. To assess whether there were changes from years 1-5 to 5-8 in physical activity levels, race-specific longitudinal generalized estimating equations were used.

What were the basic results?
This study found that the levels of physical activity decreased drastically in the adolescent cohort with the steepest decreases occurring in the year 5-8 section of the study. Over the course of the 10-year study, median physical activity decreased by 83% as a cohort. A reduction in physical activity was most predominately seen in the cohort of black girls with 56% reporting no habitual physical activity by 15–16 years of age, compared to 31% of white girls. The black cohort were reported as also having a higher body mass index (BMI) than that of the white girls, with the study concluding that heavier black and white girls participated in less physical activity than less heavy girls. This is a reason for the differences between the two racial cohorts as black girls had the higher BMI scores and less physical activity levels. Pregnancy in black girls and smoking cigarettes in white girls were also identified as a risk factor that lead to a reduction in physical activity participation.

What conclusions can we take from this research?
There is cause for concern of the health of adolescent girls as this study illustrates that there is a drastic decrease in the physical activity levels in adolescent girls regardless of race. Other research has found that this decrease in physical activity is not just exclusive to girls but is also prominent in adolescent boys especially since the introduction of technology such as computers has decreased the time spent participating in physical exercise. These declines in physical activity during the adolescent years does not set a solid foundation for a healthy, active lifestyle in adulthood with physical activity levels shown to remain stable or decrease further in adulthood compared to adolescence. It could also be concluded from this study that the lack of physical activity among adolescents could be a indicator for the increasing prevalence of adulthood obesity.

Practical advice
This research illustrates the need for interventions to be put in place to increase the level of physical activity in adolescent girls. Evidence shows that physical inactivity increases the risk of chronic diseases such as type II diabetes, cancers, and cardiovascular diseases and coupled with the results presented by this study it shows that adolescent girls are placed at high risk of such chronic diseases due to their lack of physical activity participation,. Educational resources detailing the health consequences of physical inactivity, and interventions to reduce the prevalence of smoking and pregnancy in adolescent girls should be implemented as methods aiming to reduce the prevalence of physical inactivity among adolescent girls. All people wishing to undertake a physical activity program should also be advised to see a health care professional such as a GP for a health assessment.

Further information
Further information regarding a decrease in physical activity in adolescents and how to increase physical activity levels can be found below:

http://www.health.gov.au/internet/main/publishing.nsf/content/health-pubhlth-strateg-phys-act-guidelines
 * Australia’s Physical Activity and Sedentary Behaviour Guidelines:

http://raisingchildren.net.au/articles/physical_activity.html
 * Physical Activity for Older Children and Teenagers:

http://www.apadivisions.org/division-35/news-events/news/physical-activity.aspx
 * Adolescent Girls and Physical Activity – Strengthening the Body, Mind and Soul: