Week 9 children and adolescents

Question 1

Why study young people?

Answer 1

Children are not ‘mini adults’ - growth, maturation and development can influence physiological responses to exercise

Origin of many chronic diseases lies in childhood

Critical period to establish healthy attitudes / behaviours

Question 2

Summarise the relationship between PA and health across the life course?

Answer 2

Strong evidence suggests regular exercise is associated with a lower risk of cardiac disease and premature mortality

Many disease outcomes are thought have physiological processes that start during childhood

So if we promote PA in early life this may have favourable effects in terms of delaying adverse health outcomes in later life

Question 3

What are the current PA recommendations for young people?

Answer 3

60mins MVPA daily

Should include some PA that promotes muscle and bone strength

Should reduce sedentary time

Question 4

Are young people meeting the PA guidelines?

Answer 4

In 2015 (uk) 23% of boys and 20% of girls aged 5-15yrs met the PA guidelines

Question 5

What did Cooper et al (2015) find about young people meeting the PA guidelines?

Answer 5

On average, 9% of boys and 2% of girls aged 5-17yrs met the PA guidelines.

Question 6

Summarise the longitudinal patterns of objectively measured PA

Answer 6

Boys more active than girls

Overweight individuals less active

PA levels decline through childhood into adolescence

Question 7

What is a challenge of working with this young people population?

Answer 7

It can be difficult to accurately measure their PA

Typically engage in activities that are stop start in nature

Becoming easier to measure recently with use of accelerometers

Question 8

Summarise the progression of atherosclerosis

Answer 8

Build up of fatty material to the arterial wall resulting in narrowed blood vessel

Fatty streaks (first lesion of atherosclerosis) are known to appear in both the aorta and coronary wall during the first and second decades of life

These manifestations develop quickly in terms of number and severity during adolescence into young adulthood.

Question 9

What were the key findings of pooled data from 14 studies looking at MVPA, sedentary time and cardiometabolic risk factors in young people?

• risk factors looked at - waist circumference, SBP, fasting triglycerides, high-density lipoprotein cholesterol and insulin.

Answer 9

Time spent in MVPA was associated with all cardiometabolic outcomes independent of sex, age, monitor wear time, time spent sedentary and waist circumference

Sedentary time was not associated with any outcome independent of time in MVPA

Higher levels of PA in childhood is associated with better cardiovascular health in young adulthood.

Question 10

What is flow mediated dilation?

Answer 10

The ability of the vessel to vasodilate in response to an increase in blood flow following a period of occlusion.

Question 11

What can flow mediate dilation be used as an indicator of?

Answer 11

Used as an indicator of endothelial function

Can also be used as a surrogate indicator of atherosclerosis

Question 12

What were the key results of the study by Mayer et al (2006) looking at improvement of early vascular changes and CV risk factors in children with obesity after a 6 month exercise programme?

Answer 12

Marked improvement in flow mediated dilation so suggests exercise may promote an improvement in endothelial function

Marked reductions in both systolic blood pressure and LDL cholesterol

Question 13

What are the physiological mechanisms that may explain an improvement in flow mediated dilation / endothelial function after an exercise programme?

Answer 13

Nitric oxide-induced vasodilation (increase in endothelial nitric oxide synthase)

Arterial remodelling (most likely a reduction in the thickness of the arterial wall) will increase cross sectional area of the lumen and therefore promote vasodilation.

Question 14

What are the physiological mechanisms that may explain the reduction in SBP after an exercise programme?

Answer 14

Reduction in systemic vascular resistance, probably mediated through an increase in endothelial independent vasodilation.

Structural changes may also increase the cross sectional area of the vessel which will increase the amount of resistance to blood flow and therefore reduce arterial BP.

Question 15

What is the current trends in the prevalence of overweight and obesity in children?

Answer 15

In 2018/2019, 22.6% in reception and 34.3% in year 6 were measured as overweight or obese.

However, particularly in countries with higher socio-economic status, there is some evidence that childhood obesity rates are starting to plateau (although still very high).

Question 16

Summarise the observational evidence about the relationship between PA and body fat in young people. Is there reverse causality, could it be that excess body fat predisposes children to be physically inactive?

Answer 16

Metcalf et al (2009) found that physical inactivity may be a consequence rather than a cause of excess body fat.

However, must note it is easier to measure body fat in a lab than it is to measure behaviour (in terms of PA)

Question 17

More research still needs to be done in this area, but what does a study by Adab et al (2018) suggest about the efficacy of PA interventions for the prevention of obesity?

Answer 17

Tried to encourage children to engage in an additional 30 mins of PA and ran family based dietary workshops including signposting for PA.

Found the intervention had no effect on BMI and childhood obesity compared to the control condition.

Question 18

What has been concluded about the efficacy of PA interventions for the treatment of obesity?

Answer 18

Despite the low quality of evidence, multidisciplinary interventions combining PA, diet and behaviour change promote overall small but important reductions in BMI, BMI2 score, and body mass in young people.

Question 19

What were the key findings of the study by Lee et al (2012) looking at PA as treatment for obesity?

Answer 19

Both aerobic and resistance training interventions resulted in significant reductions in body weight, BMI and waist circumference as well as increased skeletal muscle mass.

Also caused significant reductions in visceral adipose tissue and liver fat.

Question 20

Summarise the prevalence of T1 and T11 diabetes in young people?

Answer 20

T1 general diagnosed earlier in life however there is now an increase in prevalence of T11 in young people

In young people there is evidence to suggest that the decline in B cell function (T11) is faster and also linked with increased development of diabetes related complications.

Question 21

Why might it be difficult to interpret findings on insulin resistance in adolescents?

Answer 21

There are natural fluctuations in insulin resistance throughout puberty

Question 22

What were the key findings in Metcalf’s et al (2015) study about PA and mid-adolescent peak in insulin resistance?

Answer 22

Peak in insulin resistance at 12-13yrs was 17% lower in individuals with higher levels of PA. This difference diminished over the subsequent three years.

Suggests PA may be effective in reducing the normal puberty related peak in insulin resistance

Question 23

What did Lee et al (2012) suggest were the benefits of resistance rather than aerobic training)

*still get the benefits with aerobic, just more so with resistance

Answer 23

Greater increase in insulin sensitivity

Increased skeletal muscle (likely to facilitate insulin mediated glucose removal)

Increased metabolism and delivery of glucose

Increased expression of GLUT4

Increased mitochondrial size and content

Question 24

More research is needed, but what did a study by diabetes care (2013) suggest about treatment options for T11D in young people?

Answer 24

Metformin combined with lifestyle intervention was no more effective in preventing loss of glycaemic control than metformin alone and neither of these had an effect on insulin sensitivity or B cell function over a 4yr follow up.