Energy costs of physical activity

The most useful way of expressing the energy cost of physical activities is as a multiple of BMR. The physical activity ratio (PAR) for an activity is the ratio of the energy expended while performing the activity to that expended at rest (= BMR). Very gentle, sedentary activities use only about 1.1—1.2 times BMR. By contrast, as shown in Table 5.3, vigorous exertion, such as climbing stairs, cross-country walking uphill, etc. may use 6—8 times BMR.

Using data such as those in Table 5.3 and allowing for the time spent during each type of activity through the day permits calculation of an individual's physical activity level (PAL) — the sum of the PAR of each activity performed multiplied by the time spent in that activity. A desirable level of physical activity, in terms of cardiovascular and respiratory health, is a PAL of 1.7.

Table 5.4 shows the classification of different types of occupational work by PAR. This is the average PAR during the 8-hour working day, and makes no allowance for leisure activities. From these figures it might seem that there would be no problem in achieving the desirable PAL of 1.7. However, in Britain the average PAL is only 1.4, and the desirable level of 1.7 is achieved by only 22% of men and 13% of women.

The energy cost of physical activity is obviously affected by body weight, because more energy is required to move a heavier body. Figure 5.4 shows the effects of body weight on BMR and total energy expenditure at different levels of physical activity.

> 75 age

Figure 5.2 The effects of age and gender on basal metabolic rate.

80 kg

70 kg 60 kg

Figure 5.3 Body fat as a percentage of weight with age and gender.

Table 5.3 Physical activity ratios in different types of activity

1.0—1.4 Lying, standing or sitting at rest, e.g. watching television, reading, writing, eating, playing cards and board games 1.5-1.8 Sitting: sewing, knitting, playing piano, driving

Standing: preparing vegetables, washing dishes, ironing, general office and laboratory work

1.9-2.4 Standing: mixed household chores, cooking, playing snooker or bowls 2.5-3.3 Standing: dressing, undressing, showering, making beds, vacuum cleaning Walking: 3-4 km/h, playing cricket

Occupational: tailoring, shoemaking, electrical and machine tool industry, painting and decorating

3.4-4.4 Standing: mopping floors, gardening, cleaning windows, table tennis, sailing Walking: 4-6 km/h, playing golf

Occupational: motor vehicle repairs, carpentry and joinery, chemical industry, bricklaying

4.5-5.9 Standing: polishing furniture, chopping wood, heavy gardening, volley ball Walking: 6-7 km/h

Exercise: dancing, moderate swimming, gentle cycling, slow jogging Occupational: labouring, hoeing, road construction, digging and shovelling, felling trees 6.0-7.9 Walking: uphill with load or cross-country, climbing stairs

Exercise: jogging, cycling, energetic swimming, skiing, tennis, football

Table 5.4 Classification of types of occupational work by physical activity ratio; figures show the average PAR throughout an 8-hour working day, excluding leisure activities

Work intensity PAR*

Table 5.4 Classification of types of occupational work by physical activity ratio; figures show the average PAR throughout an 8-hour working day, excluding leisure activities

Light

1.7

Professional, clerical and technical workers, administrative and managerial staff, sales representatives, housewives

Moderate

2.2-

-2.7

Sales staff, domestic service, students, transport workers, joiners, roofing workers

Moderately heavy

2.3-

-3.0

Machine operators, labourers, agricultural workers, bricklaying, masonry

Heavy

2.8-

3.8

Labourers, agricultural workers, bricklaying, masonry where there is little or no mechanization

  • Where a range of PAR is shown, the lower figure is for women and the higher for men.
  • Where a range of PAR is shown, the lower figure is for women and the higher for men.
Diabetes Sustenance

Diabetes Sustenance

Get All The Support And Guidance You Need To Be A Success At Dealing With Diabetes The Healthy Way. This Book Is One Of The Most Valuable Resources In The World When It Comes To Learning How Nutritional Supplements Can Control Sugar Levels.

Get My Free Ebook


Post a comment