An Example of a Comprehensive Physical Activity Survey

The most popular survey approaches measure the type, frequency (e.g. number of times per given time-frame), duration (e.g. number of minutes per session), and estimate the intensity (e.g. degree of vigor or metabolic cost) of physical activities performed during a particular time period. It is this comprehensive assessment of physical activity that has allowed for a more sensitive discrimination between individuals of different activity levels and lends itself to subanalyses based on type, duration, and intensity of activity. This approach has served as the basis for much of the epidemio-logic research relating physical activity to the prevention of cardiovascular and other diseases.

As described in Figure 5.3, the data obtained from a more extensive questionnaire format give

Intensity weighting 5 METS or (5 kcal/kg .h)

30 MET-hours per week or 30 kcal/kg per week

21CC kcal/week

Figure 5.3 Steps in the computation of the summary estimates for the physical activity questionnaire

Intensity weighting 5 METS or (5 kcal/kg .h)

Figure 5.3 Steps in the computation of the summary estimates for the physical activity questionnaire the researcher options to analyze data at several different levels. Multiplying the number of times per week (or month) of participation by the number of hours (or minutes) per time leads to an estimate of total duration of physical activity within a specific time frame. Comparisons can be made at this step in this process by comparing individuals based on the total time (frequency and duration) spent participating in physical activities (Figure 5.3). If possible, time spent in each activity can then be multiplied by an estimate of the relative intensity of that activity. These estimates are obtained from the literature and correspond to how vigorous the specific activity is thought to be. All of the activities are then summed and expressed in 'MET-hours per week' (or kcal/kg per week), which can be converted to kilocalories per week if one knows the body weight of the individuals. However, this involves making an assumption about the weight of the individual throughout the time-frame which is being assessed. As an example of this computation procedure, the Modifiable Activity Questionnaire assigns a specific MET level to each activity based on average levels of energy expenditure determined from the literature (43).

Rather than weighting each specific activity by its relative intensity, some surveys weight groups of relatively similar activities. For example, the Harvard Alumni Questionnaire assigns 5.0 kilo-calories per minute to a group of activities deemed to be of low cardiovascular intensity (e.g. gardening, bowling, etc.), 7.5 kilocalories per minute to moderate intensity activities (e.g. dancing) and 10 kilocalories per minute for high-intensity activities (e.g. running) (5).

Regardless of the method of intensity-weighting used, several assumptions are made by the researcher when incorporating intensity into the analysis process: Lists of MET values for most activities are available and provide the basis for calculations in physical activity questionnaires. When obtaining a MET or kcal value from a list, it is assumed to be representative of the manner in which the activity was performed by the individual. Since skill level varies for sporting activities and a wide range of paces may be selected for activities like cycling, walking, jogging, there may be considerable variation in the actual energy expenditure across subjects. Weighting physical activities by intensity also assumes that body-

weight is proportional to resting metabolic rate and that the relative increase in metabolic cost of a specific activity above resting is constant from person to person regardless of bodyweight.

Because of these assumptions made with physical activity questionnaires, estimates of physical activity obtained from them give a relatively limited assessment of absolute energy expenditure. However, since physical activity represents the most variable component of total energy expenditure, they are valuable in relative terms and can be used to rank individuals or groups of subjects within a population from the least to the most active. This relative distribution of individuals based on their reported levels of physical activity can then be examined according to its relationship to physiological parameters and disease outcomes.

100 Bowling Tips

100 Bowling Tips

Playing bowling with your friends can help you decide if it is indeed the hobby that you want to invest your time on today. Aside from that, it can help you get a better feel of the sport. More importantly, when you play with your friends, it would become a more fun activity, which you can look forward to each week.

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