actions performed by individuals in their daily lives , such as sleeping , walking , 
 exercising , and watching television , are described as physical behavior .
monitoring of such 
 behavior has helped researchers to broaden their perspective about prevention and 
 rehabilitation of patients with various diseases and disorders1 , 2 . with advances in 
 technology , various novel methods have been developed to assess physical behavior , but 
 conventional methods are still relevant and easy to administer3,4,5 .
overweight is a major risk factor for poor health in children6 , and various studies have reported a significant rise in the 
 incidence and prevalence of obesity in overweight children7,8,9,10 .
overweight children are 
 likely to become overweight adults , with associated cardiovascular and metabolic 
 diseases11,12,13 .
change in physical 
 behavior as a component of lifestyle modification in treatment of obesity has been widely 
 recommended14 , but its role as a risk 
 factor in the development of obesity has not been well documented .
lack of physical activity 
 may be a cause of overweight , and may be associated with a sedentary lifestyle , including 
 increased duration of tv watching and internet use15 .
time spent while using such media comprises sedentary activity , 
 and is negatively correlated with physical activity scores and positively correlated with 
 body composition indices , which lead to overweight16 .
sedentary behavior is an independent risk factor for development 
 of overweight and associated risk factors that may differ with gender17 .
although it is a relative term , more time spent in 
 sedentary activities does not necessarily mean less physical activity18 .
besides genetics , diet , and hormonal levels , the level of physical activity is also a major 
 determinant of normal growth , development , and maturation in children19 , 20 .
physical 
 activity also lowers the genetic predisposition to increased body mass index ( bmi ) that in 
 turn leads to obesity21 , 22 .
hence it is important to assess physical activity using 
 standardized measures in public health to identify the risk factors associated with obesity , 
 especially in children1 , 24 .
assessment of physical activity can include intensity , 
 frequency , duration , type , or mode25 . 

appropriate methods for assessment also depend on the setting ( indoors or outdoors ) , and 
 location and reason ( leisure , work , etc . ) for activity26 .
various subjective and objective methods have been used to measure daily physical 
 activity27 , 28 .
these include physiological methods such as oxygen consumption and 
 heart rate , and behavioral tools such as questionnaires and interviews.27 , 29,30,31 . for better 
 generalizability of data on physical activity
, these measures should be reliable , valid , and 
 easy to administer , to meet the needs of global cultural diversity4 , 10 .
there have been 
 no recent reports comparing such modalities for use by clinicians and researchers32 .
hence , this article reviews some of the 
 methods used to assess physical activity , and describes their advantages and disadvantages . 

the list of methods presented in this article is inclusive but not exhaustive , and there are 
 no commercial relationships with manufacturers .
databases including pubmed , medline , and google scholar were searched for literature , using 
 the key words obesity , physical activity , and physical behavior monitoring .
after elimination of duplicate papers , relevant papers published in the last 20  years were 
 studied . these included randomized clinical trials , cohort studies , and systematic 
 reviews .
in this section , we evaluate physical activity monitoring methods based on type , accuracy , 
 ease of administration , cost , availability , and quality , for use in daily living .
the choice 
 of method used to measure physical activity depends on the type , duration , and reason for 
 the physical activity .
self - reporting methods : these include subjective measures such as 24-hour recall through 
 questionnaires , interviews , and activity diaries33 .
these are widely used to assess physical activity , but have 
 advantages and disadvantages34 , 35 .
their affordability , adaptability , and ease of use allow 
 them to obtain both qualitative and quantitative data about the level of physical activity 
 for a larger population10 .
however , there 
 is a possibility of overestimation36 , 37 , with errors in reporting , validation of 
 data , and repeatability of measurement38 , 39 . although various questionnaires are 
 available , their reliability and validity has not been reported35 , 40 .
two of the 
 most popular self - reporting methods are the following : 1 .
the international physical activity questionnaire ( ipaq ) is a popular method of 
 measuring physical activity patterns , and can be administered by telephone interview or 
 self - reporting2 , 35 .
it can measure the nature of physical activity with a minimum 
 duration of 10 minutes at moderate and vigorous intensity levels35 .
literacy rate , cultural differences , and climate induce differences 
 in the nature of physical activity in developing and developed countries42 , that lead to the need for a more globally 
 acceptable questionnaire .
the global physical activity questionnaire ( gpaq ) was developed by the world health 
 organization in 20023 .
it was based on the 
 ipaq and consists of 19 questions regarding physical activity under domains of work , 
 transport , and discretionary activities42 .
studies have indicated that gpaq is a suitable , reliable , and widely 
 accepted instrument for physical activity assessment in large populations across different 
 cultures10 .
immaturity , difficulty in recall , and variable patterns of activity in children25 , and general decline in the elderly make 
 self - reported physical activity assessment different in these groups43 .
the children s physical 
 activity questionnaire and the youth physical activity questionnaire were devised for 
 younger age groups , but studies were unable to establish accurate estimates of the time 
 spent in moderate and vigorous intensity physical activity and energy expenditure45 .
for the elderly , the modified baecke 
 questionnaire and the yale physical activity survey have been discussed in the literature , 
 but individual cognitive levels and a wide range of activity patterns are expected to affect 
 the data46 .
pedometry : pedometers are motion sensors that are typically worn on the waist to count the 
 number of steps during locomotion47 . they 
 are designed to capture vertical motion of the hip joint with movement48 .
objectivity , small size , easy availability , and low cost 
 make pedometers popular among physicians who prescribe them for patients for self - monitoring 
 and providing feedback on daily physical activity49 , 
 50 . unlike self - reporting methods , 
 these give a better picture of physical activity by measuring footsteps37 .
however , they can not capture activities that do not 
 involve displacement , like lifting weights , isometric exercises , or activities that involve 
 variable speed or upper body motion only , such as cycling or swimming47 , and can not measure temporal variables of movement , 
 distance traveled , and intensity and duration of physical activity51 , 52 .
various studies that compare different available models on the market report wide variation 
 in their measurements53 , 54 , which must be considered in research55 . however , there are also studies that report these methods 
 to be valid for physical activity measurement in comparison to accelerometers , observation , 
 and self - reporting methods56 , 57 .
accelerometry : accelerometers are the most objective method for measurement of physical 
 activity , especially in outdoor settings33 .
these devices use various technologies such as piezoelectric 
 effects to measure acceleration along a movement axis58 .
depending on the model , they can be worn on the wrist , waist , or 
 foot ; they have a comparatively lower cost and are easy to use59 .
newer variants also have the capacity to measure 
 acceleration in vertical , horizontal , and mediolateral planes60 , 61 .
in addition to 
 providing feedback , they can also measure temporal parameters and allow data transfer for 
 further calculations and later use62 . 

sedentary activity is classified as < 100 counts / min , while < 1,952 counts / min , 
 1,9525,724 counts / min , and > 5,724 counts / min are regarded as light , moderate , and 
 vigorous physical activities , respectively63 .
these devices must be worn continuously 
 throughout the recoding period42 . despite being widely used
, accelerometers lack the capacity to measure physical activity 
 that involves only upper body movements , such as the vertical motion component during 
 cycling , and activity while carrying loads , and they underestimate recording while walking 
 on inclined surfaces47 , 65 .
studies have shown differences in recording within and 
 between models66 , and in use in the 
 pediatric age group67 .
heart rate monitors : heart rate is used in exercise prescriptions as it increases linearly 
 with moderate to strenuous physical activity68 .
small size and low cost of monitors make 
 these popular for measurement of habitual physical activity with or without 
 displacement47 .
commonly available 
 heart rate monitors are attached to the chest with a strap or electrodes , and are not always 
 feasible for use , as they are difficult to mount without assistance , and because electrode 
 placement may leave irritation and marks on the skin70 .
although these devices are shown to have high reproducibility71 , there are reports that they are less accurate during low 
 intensity physical activity and in cases where the heart rate is affected by factors other 
 than activity , e.g. , high temperature , humidity , or stress72 .
absolute heart rate values and heart rate indices , including 
 activity heart rate , are reportedly derived from actual readings to obtain more meaningful 
 values and overcome such limitations73 . 

combination devices : each of the methods mentioned above have their own advantages and 
 disadvantages . to make the most out of the data recorded and recent advances in technology
it was first reported in 1988 that the combination of heart rate 
 and motion analysis can be more meaningful than the individual measurements74 . since then , various studies have found 
 that such devices can improve accuracy of measurement during activities of daily living75 .
these may combine heart rate and movement 
 sensors , movement and temperature sensors , or multiple sensors to record motion of different 
 body segments25 .
in a situation in which low physical activity takes place at high speed ( e.g. , riding in a 
 car ) , use of an accelerometer along with heart rate measurement would provide a more 
 meaningful estimate than either alone47 . 

multi - sensor devices can be complex at times , involving various circuits and wires , and are 
 costlier than currently available devices , making them difficult to use in research 
 involving a large number of subjects25 . 

although such devices can provide more accurate results , their feasibility , reliability , and 
 validity should be verified before they are more widely used , especially in research25 . in conclusion
, physical inactivity often leads to serious health hazards , especially in 
 overweight people .
the latest methods are required in research , clinical use , and daily life 
 applications for physical behavior monitoring and tracking of changes in physical activity 
 patterns in overweight and obese patients .
researchers may choose devices providing more accurate measurements , while 
 clinicians may prefer portability and affordability for patients .
 [ purpose ] overweight and obesity are major risk factors for poor health , especially in 
 children . reduced physical activity , prompted by a sedentary lifestyle , is a major 
 contributor . 
 hence , it is important to assess physical activity using standardized methods 
 in public health to identify the risks associated with obesity . 
 there have been no recent 
 reports comparing such modalities for use by clinicians and researchers . in this article , 
 
 some of these methods for use in the assessment of physical activity are reviewed , and 
 their advantages and disadvantages are described . [ subjects and methods ] electronic 
 databases including pubmed , medline , and google scholar were searched for literature , 
 using key words obesity , physical activity , and physical behavior monitoring . 
 [ results ] 
 with advances in technology , various novel methods have been developed to assess physical 
 behavior , but conventional methods are still relevant and easy to administer . 
 [ conclusion ] 
 there are various measurement options available . 
 researchers may choose devices providing 
 more accurate measurements , while clinicians may prefer portability and affordability for 
 patients . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION