Measurement of PA and SB

Question 1

Give reasons why it is necessary to measure children’s PA and SB

Answer 1

allows researchers to establish links between the two behaviours

allows determination of correlations between behaviours and health outcomes

can then re-measure to determine if an intervention has been successful

Question 2

Explain why it can be complicated to measure child PA

Answer 2

For different people, activity happens at different times of the day and in different ways

A child will demonstrate lots of different behaviours in one day, so can be hard to capture them all

Children’s behaviour is very sporadic and very short lived (80% of PA bouts are below 10 seconds)
This is very hard to capture, especially with questionnaires

Question 3

When measuring child PA, what variables need to be measured

Answer 3

Duration

Intensity (HR or speed of movement or energy expenditure)

Time of day when children are most active

Type of activity they’re doing

Question 4

How can information about the timing and type of PA be used

Answer 4

to design interventions

target times when least PA occurs
Know what type of PA children are doing and therefore clearly like to do

Question 5

Other than information about the PA, what other variables should be measured

Answer 5

Health outcomes associated with a certain level of energy expenditure

Question 6

What three things need to be considered when deciding which method to use to determine levels of PA

Answer 6

Accuracy
validity
feasibility

Question 7

What are the limitations of using questionnaires to determine a child’s level of PA

Answer 7

Large cognitive burden to think about and remember all activity (even more of a problem in younger children)

Children may not understand the wording of a question

Children may get bored and not complete it

Parent report is often used, but the child isn’t often with them all day

Bias, often = over-reporting

Inaccurate recall bc of the sporadic nature of child PA it’s hard to accurately recall

Is the time when you’re recording representative of a normal day

Question 8

What are the limitations of using accelerators to determine PA levels

Answer 8

People often fail to return the monitors which are quite expensive

People may not comply or may not remember to put on

hard to differentiate between sleep and SB

might not have always been the child wearing it, could have been a friend etc

REACTIVITY (upregulation, not representative)
usually around 5% more activity on day 1 vs other days

Question 9

how do researchers overcome the issue of reactivity when using accelerometers to capture data?

Answer 9

wear for 8 days and exclude the first day

Question 10

Give reasons why it is not ideal for accelerometers to be placed on the wrist

Answer 10

over-estimates amount of activity and under-estimates amount of time spent sitting because children do a lot of writing which causes movement

Question 11

Why is it best to get children to wear the accelrometers for as long as possible

Answer 11

data will be more reflective of the daily average

data will be more reliable

there is a higher correlation between activity on each day

child’s routine is more variable so more days = more representative

Question 12

Briefly explain how accelerometers were validated

Answer 12

children doing various activities whilst undergoing indirect calorimitry and wearing accelerometers

then determine which number of counts corresponds to which level of PA

regressing analysis relates the amount of counts per minute to the intensity of PA

Question 13

Why is it hard to compare between studies using accelerometer data?

Answer 13

different threshold values used

so differences in amount of PA at each intensity

A child’s activity would be classified in different ways by different papers

Question 14

What is an epoch and how are they used to determine the intensity of PA

Answer 14

A period of time, over which the number of accelerations is counted

so a threshold would be a certain number of accelerations in a certain period of time, above which PA is classed as MVPA for example

Question 15

What are the reasons for using a higher sampling frequency

Answer 15

more sensitive at picking up the sporadic activity of children

easier to differentiate between moderate and intensity activity

Question 16

What is a possible limitation of using a higher sampling frequency?

Answer 16

Over-estimate sedentary behaviour (bc might not reach threshold even if are moving)

Question 17

why are questionnaires not desirable for measuring SB in children

Answer 17

struggle to remember how long they sat for

don’t follow a set routine like adults do, therefore also harder to estimate

Question 18

What is a domain specific questionnaire for measuring SB

and what limitations are there with these

Answer 18

asking how long children spend doing a specific SB e.g watching TV

they may be outdated and not include newer behaviours e.g tablets
time consuming
cognitive burden
tend to over-report due to over-thinking caused by the domains

Question 19

How are accelerometers used to measure SB

what is the limitation of this

Answer 19

a proxy measure, which measure the absence of movement (<100 counts per min = SB)

could measure <100 when standing so this isn’t technically a SB

Question 20

How does an inclinometer work

Where it is usually worn

Answer 20

device which measures the angle of inclination
(above a certain angle it is very likely that a person is standing)

mid-thigh

Question 21

explain how an inclinometer is used

Answer 21

when below a certain angle, a person is considered to be sitting or reclined

participants then asked to complete a diary of when asleep so that this can be partitioned out of the data

Question 22

what are the limitations of using inclinometers

Answer 22

very expensive 
uncomfortable to wear 
people may be allergic to the adhesive 
forgetting to put it back on 
time consuming to apply 
safeguarding and cultural issues to applying device to this are

Question 23

Why are self-report methods of data collection regarding PA useful

Answer 23

simple and cheap relative to other methods

can get info about the type and context of PA

Can get info from a relatively large sample

Question 24

What are the limitations of using self-report measures in children

Answer 24

Sporadic nature and short duration of PA, makes it very hard to accurately recall

Children over-estimate the duration and intensity of PA

Low validity in younger children, not really suitable for <10

Question 25

What is a proxy report and in what age of children should they be used

why are they used in these children

Answer 25

asking teachers or parents to report how much PA a child does

avoids the recall bias caused by their limited cognitive ability

Question 26

What limitation has been found with the use of proxy measures

Answer 26

not well correlated with objective measures of PA

Question 27

what three variables can be objectively measured with a HR monitor

Answer 27

frequency
duration
intensity

Question 28

Provide some critique of the use of HR monitors to measure PA levels

Answer 28

Relatively cheap and non-invasive

limited correlation between HR and energy expenditure at high and low intensities

HR - energy expenditure relationship has many influencing factors such as age, fitness and temperature

An impractical method for large scale studies

HR response is delayed after onset of activity which could mask intermittent activity

Question 29

Explain how an accelerometer is used to determine PA levels

Answer 29

worn around the waist

records frequency and magnitude of body accelerations

this is then digitalised to give an activity count

activity count is summed over a set period of time and then entered into an equation to give the intensity of PA

Question 30

discuss the factors which are considered when determining epoch length

Answer 30

long epoch could mask spontaneous and discontinuous play
(will result in an under-estimation of high intensity work)

shorter epochs give a better estimation of time spent and MVPA

Question 31

What needs to be taken into consideration when deciding how long an accelerometer should be worn for

Answer 31

4-5 days needed to get reliable results and good correlation between PA levels on each day

MVPA varies significantly between weekend and weekday so need to include at least one weekend day

Question 32

give some limitations of the use of pedometers

Answer 32

only count steps so would miss PA such as riding a bike

Question 33

what are the advantages of the direct observation method

Answer 33

objective data 
gives context of PA
gives types and intensity of PA
can be used in many different settings 
now computer programmes which can analyse video

Question 34

what are the limitations of the direct observation method

Answer 34

highly trained people needed

can only do a small sample

Question 35

In what ways can SB be measured

Answer 35

assess time doing screen based activities via:

self report or survey 
Parental reports 
direct observation 
accelerometers (<100 count)
May miss other types of SB such as homework, motorised transport, sitting and talking