PHYSICAL ACTIVITY IN CHILDREN AND ADOLESCENTS ASSESSMENT OF PHYSICAL ACTIVITY LEVELS IN CHILDREN CURRENT METHODS – Written by Badriya Al Hadabi, Oman The term ‘physical activity’ has been Several classification units are used in considerably with respect to the quantity described as referring to any bodily measuring physical activity behaviours. and quality of information they can provide movement produced by the skeletal These include the ratio of the activity energy for the type, frequency, duration and system and muscles that results in energy expenditure to the resting energy cost, intensity of the activity. Available evidence expenditure1,2. Free-living physical activity oxygen consumption per unit of body mass indicates that self-report measures have behaviours in children and adolescents per unit of time (mL/kg/min), multiples many advantages such as the ability to are considered one of the most complex of resting metabolism or ‘metabolic record physical activity type and context in domains to assess. Usually, physical activity equivalents’ (METs)4, duration of activity a historical way, at low cost and with ease domains include all types of activities bout spent at sedentary, light, moderate and of administration5. Despite the positive performed during free-time or leisure-time, vigorous intensity levels and the total time points of self-report methods, studies have transportation activities, all tasks performed spent in bouts of moderate-to-vigorous documented that children aged 10 years and in the home environment, physical physical activity (MVPA) combined3. younger are unable to recall their previous education sessions and break-time at school. activities accurately6,7 because the activity Further, physical activity behaviours can be SELF-REPORT MEASURES bouts are often very short and spontaneous, characterised according to the dimensions Self-reporting is one of the most making recall difficult8. Janz et al9 illustrated of type, intensity, frequency and duration. common subjective methods used in that self-report questionnaires completed Thus, measuring physical activity epidemiological and surveillance studies. by young children had a poor-to-moderate behaviours in children and adolescents is When surveying children, this method correlation for activity level compared with extremely difficult, making it is necessary to includes self-administered recalls, objective measurement (accelerometers) have valid and reliable tools that are capable interviewer administered recalls, direct and r=0.03 compared with r=0.51. Children were of including all of the relevant dimensions proxy reports completed by either parents also unable to quantify the duration of the and domains3. or teachers. Self-report measures vary activities they had performed6. Sallis et al7 240 evaluated 23 self-report measurements and DIRECT OBSERVATION specific for use during physical education illustrated that on average children had Direct observation is considered one of sessions, including the Children’s Physical lower reliability and validity coefficients the most appropriate means of measuring Activity Form (CPAF)10 and the System compared to adolescents when using self- physical activity and monitoring patterns for Observing Fitness Instruction Time report measures. Further, it was found of activity10. Generally, direct observation (SOFIT)12. However, other systems can be that children aged 10 or younger did not involves observing the physical activity used in different settings, for example, the understand the concept of physical activity6. behaviours of a child at school or at home Children’s Activity Rating Scale (CARS)13, Trost3 investigated the ability to understand for a specified period. Children’s physical the Fargo Activity Time-sampling Survey the concept of physical activity in Year 4 activity behaviour is usually recorded into (FATS) and the Behaviour of Eating and (8 year-old) children. Results suggested a coding form at a regular interval, ranging Activity for Children’s Health Evaluation that 60% of Year 4 children were unable to from 5 seconds to 1 minute3. Typically, System (BEACHES)10. The most recent and differentiate between sedentary activity this method usually involves observing a widely used direct-observation systems (e.g. computer games) and active leisure child’s behaviour in real life or using video are the System for Observing Play and pursuits (e.g. outdoor games). Children are recording for a certain period. The data Leisure Activity in Youth (SOPLAY) and less able than adults to self-report physical recorded can then be converted to a score. the Observational System for Recording activity, as they have lower cognitive One of the important advantages of direct Physical Activity in Children–Preschool function than adults, making them less observation is the ability not only to record Version (OSRAC-P)14. Direct observation has accurate in recalling the activity frequency, the activity type but to capture the activity proven to be a valid and reliable method duration and intensity10. Generally, self- pattern, frequency, duration and intensity, of measuring physical activity in children, report measurements revealed a low validity as well as the physical and social context (i.e. as it has been validated against heart rate coefficient in measuring children’s physical environment) in which the physical activity (HR) r=0.61 to 0.7215 and against oxygen activity. As such, it is necessary to use more occurs3,11. uptake (VO2)11. Nevertheless, these methods appropriate objective methods to measure There are several different observational are costly in due to the investment required physical activity in children, particularly in systems available to measure physical to train observers and required length of children of primary-school age. activity. A number of these systems are the observation period11. In addition, the HEALTHY LIFESTYLE TARGETED TOPIC 241 PHYSICAL ACTIVITY IN CHILDREN AND ADOLESCENTS unexciting data and coding requirements the subject directly breathing a constant easily used in normal daily life, it is quite are considered one of the most significant composition of ambient air using a difficult to implement with children, as limitations to direct observation of breathing valve, with the expired air exiting it is difficult to obtain consent due to the physical activity3,10. These methods require through a gas meter. The difference between need for direct supervision/monitoring by high experimental effort physically and the percentages oxygen and carbon dioxide parents over multiple days of calorimeter financially, and this is why they are not in the inspired air and expired air indirectly measurements10. In addition, DLW has generally used in large population studies. expresses the energy expenditure during several major weaknesses. For example, Children may also change their behaviours the monitoring period. Open-circuit isotopes of water are very expensive due to the presence of the observer. spirometry uses lightweight equipment, and difficult to obtain, which means which means there is more opportunity this technique is not suitable for large DIRECT AND INDIRECT CALORIMETRY for it to be used under different conditions studies3,10. Despite the need for an accurate Direct and indirect calorimetry are to measure different types of physical dietary record during measurement considered to be primary objective measures activity intensities and modes of activity, periods of energy expenditure, DLW does of physical activity10. In fact, in 1890, Atwater making it more versatile than closed-circuit not provide any information on physical and Rosa used the first direct-calorimetry spirometry4. In addition, no differences have activity patterns16 and can only obtain the measurements in humans. This method is been found between the results provided calculation of the total energy expenditure. based on measuring the heat produced by by the direct- and indirect-calorimetry the body as a direct measurement of energy methods. As such, indirect calorimetry can HEART-RATE MONITORING expenditure. The direct-calorimetry method be considered easier to employ and less HR monitoring is widely used as an uses a closed chamber attached to associated costly compared to direct calorimetry. objective method to measure physical equipment where subjects can live, eat, activity in children and adolescents17,18. It sleep and exercise while heat production is DOUBLY LABELLED WATER is also frequently used to define children’s measured. Direct calorimetry is well known The doubly labelled water (DLW) physical activity patterns19,20, estimate as the ‘gold-standard’ measurement tool technique is an objective, potentially energy expenditure (both in controlled of human energy expenditure; however, gold-standard method to estimate energy and free-living environments)10,21,22 and in practice, it is an expensive, complex and expenditure related to physical activity to validate other methods used to assess time-consuming method and restricted to in free-living children and adolescents3. energy expenditure and physical activity use under laboratory conditions4. DLW has been well described3,10 and (e.g. accelerometers)9,21. HR monitoring is The indirect-calorimetry method was validated in adults and children against a simple, relatively inexpensive method of developed based on the knowledge that the indirect calorimetry. Although DLW can be monitoring physical activity that causes body’s metabolic reactions are ultimately dependent on oxygen.