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TABLE 6-7 Partition of Energy Expenditure in Three Climates in 1955

 

Climate

Task

Cold, Ft. Churchill Canada (-22.5°F)

Temperate, Natick Massachusetts (72°F)

Hot, Yuma Arizona (90.5°)

 

8*

8*

11*

Walking (3.41 mph, level terrain)

kcal per hour

413

318

350

kcal per kg per hour

4.82

5.12

5.26

Resting and sedentary activity,

kcal × kg0.7 per hour

4.58

4.62

4.40

* Number of subjects.

Body weight plus weight of clothing.

Includes dietary-induced thermogenesis.

SOURCE: Adapted from Welch et al. (1958).

conducted in a hot or comfortable environment, the partitioning of energy expenditure was different, that is, less aerobic expenditure and greater anaerobic expenditure in the hot environment (Table 6-9). The results were subsequently confirmed by Dimri et al. (1980). The hypothesized explanation for this partitioning was the diversion of a significant amount of blood from the muscles to the skin for thermoregulation in hot environments. Although

TABLE 6-8 Mean Oxygen Uptake Responses to Exercise Before (B) and After (A) 8 Days of Heat Acclimation

 

Mean Oxygen Uptake (ml per m2 per minute)

 

41W, 23°C

82W, 23°C

41W, 39.4°C

Group

B

A

B

A

B

A

Trained (n = 7)

623

570*

1075

960*

634

569*

Untrained (n = 7)

668

577*

1061

985*

680

586*

Unfit (n = 7)

615

531*

1050

932*

618

520*

Control (n = 5)

625

578

1068

1030

611

615

NOTE: Heat acclimation regimen = 3 hours of exercise per day at 41 watts, Tdb = 39.4°C, Twb = 30.3°C, where Tdb = dry-bulb temperature and Twb = wet-bulb temperature.

* p ≤ 0.05.

SOURCE: Adapted from Shvartz et al. (1977).



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