Physical activity and physical activity induced energy expenditure in humans: measurement, determinants, and effects

Abstract

Physical activity is defined as any bodily movement produced by skeletal muscles that results in energy expenditure. The doubly labeled water method for the measurement of total energy expenditure (TEE), in combination with resting energy expenditure, is the reference for physical activity under free-living conditions. To compare the physical activity level (PAL) within and between species, TEE is divided by resting energy expenditure resulting in a figure without dimension. The PAL for sustainable lifestyles ranges between a minimum of 1.1-1.2 and a maximum of 2.0-2.5. The average PAL increases from 1.4 at age 1 year to 1.7-1.8 at reproductive age and declines again to 1.4 at age 90 year. Exercise training increases PAL in young adults when energy balance is maintained by increasing energy intake. Professional endurance athletes can reach PAL values around 4.0. Most of the variation in PAL between subjects can be ascribed to predisposition. A higher weight implicates higher movement costs and less body movement but not necessarily a lower PAL. Changes in physical activity primarily affect body composition and to a lesser extent body weight. Modern man has a similar PAL as a wild mammal of a similar body size.

Keywords: accelerometer; age; body composition; chronic disease; doubly labeled water; energy intake; exercise training; predisposition.

FIGURE 1

Principle of measurement of carbon dioxide production with doubly labeled water (²H₂¹⁸O). After administration of water labeled with heavy oxygen (¹⁸O) and heavy hydrogen (²H), the two isotopes mix with the body water, where ¹⁸O exchanges with CO₂ in the bicarbonate pools as well. Thus, the elimination rate of ²H (K₂) is a measure for water loss (rH₂O) and the elimination rate of ¹⁸O (K₁₈) is a measure for rH₂O plus carbon dioxide production (rCO₂), and rCO₂ = K₁₈–K₂.

FIGURE 2

Components of total energy expenditure for an average young adult woman and man as adapted from Westerterp et al. (1996).

FIGURE 3

Frequency distribution of the value of the physical activity level, total energy expenditure as a multiple of basal metabolic rate, in a group of women (closed bars) and men (open bars), where subject characteristics are presented in Table 1.

FIGURE 4

Time spend in activities of low intensity (open bar), moderate intensity (stippled bar) and high intensity (closed bar), expressed as a percentage of the active time, for children, adults and elderly; *P < 0.05 for difference between adults and children; and **P < 0.01 for difference between adults or elderly and children (After Hoos et al., 2004).

FIGURE 5

The physical activity level, total energy expenditure as a multiple of basal energy expenditure, before (open bar) and at the end of a training program (closed bar), for eight studies displayed in a sequence of age of the participants as indicated on the horizontal axis. The horizontal broken lines denote the average physical activity level of 1.75 and the ceiling value of 2.00 for non-athletes; * P < 0.05; and ** P < 0.01 for difference with before training program (After Bingham et al., 1989; Blaak et al., 1992; Goran and Poehlman, 1992; Westerterp et al., 1992; Kempen et al., 1995; Van Etten et al., 1997; Hunter et al., 2000; Meijer et al., 2001).

FIGURE 6

Free-living physical activity level plotted as a function of physical activity level in the confined environment of a respiration chamber, with the line of identity (dotted) and the linear regression line (continuous) (After Westerterp and Kester, 2003).

FIGURE 7

Physical activity level by body mass index category for subjects aged 18 to 50 year from Table 1. The horizontal broken line denotes the average physical activity level of 1.75.

FIGURE 8

Body mass change in patients with chronic obstructive pulmonary disease over three months after clinical rehabilitation, plotted as a function of the physical activity level (After Goris et al., 2003).

FIGURE 9

Frequency distribution of the body mass index of subjects that successfully trained to run a half marathon (open bars) and of the dropouts (stippled bars), the latter were 9 out of 32 subjects (After Westerterp et al., 1992).

FIGURE 10

Fat mass change from before until 40 weeks after the start of a training period to run a half marathon plotted versus the initial body fat percentage for women (closed dots) and men (open dots) with the calculated linear regression line for men (After Westerterp et al., 1992).

FIGURE 11

Time trend of the physical activity level for a population around Maastricht in the Netherlands (After Westerterp and Speakman, 2008).

FIGURE 12

The physical activity level in wild terrestrial mammals, plotted as a function of body weight. The value for modern man is indicated as a closed square (After Westerterp and Speakman, 2008).