Anthropometry of an aging work force.

Faced with an aging labor force, industrial planners are worried about the possible need to redesign jobs and workspaces in the future. One area of concern is the changes that occur in body size characteristics as people age. Although no true database for the anthropometry of the American worker exists, available surveys and studies that include older individuals (40 to 70 years), and errors associated with these studies, are discussed. Using sample mean values from selected cross-sectional and longitudinal studies, the changes in weight and selected body dimensions are traced from the third to the eighth decade of life. As a practical exercise, age-associated changes in a number of workspace dimensions are tested against recommended design values for seated work stations. While acknowledging the need for flexibility in future workplace designs the authors conclude that age-related changes in body size are insufficient in themselves to justify the resizing of existing ergonomically-designed workplaces.

Calorimetry with heat flux transducers: comparison with a suit calorimeter.

Regional and total body heat loss rates of human subjects at rest were measured simultaneously by means of an array of heat flux transducers and with a tube suit calorimeter. Conditions ranged from thermal comfort to strong cooling. A high degree of correlation was found between heat loss rates determined by the two independent techniques. For the head and arms, the transducer array system measured less heat loss than the suit. For the torso and legs, measurements by the two methods were equivalent. For the whole body, the transducer system yielded a heat loss rate 87% of the suit calorimeter value.

Adaptation to overeating in lean and overweight men and women.

In groups of four, men and women in their 40s and 50s, some of them lean and some overweight, overate for 30 d by 1000 kcal/d (4186 kJ/d) more than they needed to maintain weight. On an average dietary mixture for Americans they gained a mean of 2.68 kg, and on a diet high in carbohydrate (60 per cent of energy) they gained 2.73 kg. However, on a diet high in protein and fat (70 per cent of energy), they gained significantly less, 1.75 kg. On all three diets the subjects should have gained 5 kg, if adipose tissue has an energy density of 6 kcal/g, and had there been no adaptation. There was adaptation, as evidenced by an average 7 per cent increase in thermogenesis, which was measured by 24-h direct and indirect calorimetry. Energy balances were calculated from: bomb calorimeter values for food and body waste; change in fuel stores from body composition measured by densitometry; and daily expenditure estimated from the net food intake needed to maintain body weight during a 30-d control period. During overeating, energy intake matched energy losses (including fuel storage) for the average diet and the high-carbohydrate diet, but on the diet high in protein and fat energy intake exceeded losses by more than 500 kcal/d (2093 kJ/d). Thus smaller than expected weight gains from overeating (luxuskonsumption) were largely explained by increased thermogenesis, except when the diet was high in protein and fat. Lean and overweight subjects did not differ in weight gain, loss of energy in urine and faeces, or thermogenesis from overeating.

Induced venous pooling and cardiorespiratory responses to exercise after bed rest.

The purpose of this study was to deliberately induce venous pooling the lower extremities of bed-rested subjects to determine whether such distention may reverse the reduction in maximal O2 uptake that has regularly been observed. Bed-rest deconditioning was assessed in eight healthy male subjects by measuring submaximal and maximal O2 uptake (VO2 max), ventilation, and heart rate (HRmax) before and after 15 days of bed rest. During bed rest four subjects in the experimental group received daily treatments of venous pooling for 210 min/day with a reverse gradient garment (RGG), whereas the four subjects in the control group received no treatment. Compared with prebed-rest values, VO2max was reduced by 14.0 (P less than 0.05), HRmax was increased by 4.2 (P less than 0.05), and endurance time for the exercise test was decreased by 9.2% (P less than 0.05) in the control group. In the RGG group, VO2max, HRmax, and endurance time were essentially unchanged after bed rest. The plasma volume (PV) of the control group decreased by 16.7 (P less than 0.05) after bed rest compared with a 10.3% (not significant) reduction in the RGG group. The percent delta PV was related to the percent delta VO2 max (r = 0.75, P less than 0.05) and percent delta HR max (r = 0.65, P less than 0.05). The data support the hypothesis that the lack of venous pooling and associated fluid shifts contribute the decrement in VO2 max associated with bed-rest deconditioning.

Energy balance in man measured by direct and indirect calorimetry.

In six 24-hr measurements of energy balance, direct and indirect calorimetry agreed within +/-3%, which is probably the range of experimental error. But in seven other 24-hr periods there was disagreement in the range of 8 to 23%, and these were usually days when the subjects ate much less than they spent metabolically. Our direct calorimeter is an insulated, water cooled suit. Continous measurements of O2 consumption and CO2 production provided data on metabolic expenditure (M) by indirect calorimetry. The 24-hr values for M matched the energy losses within +/-60 kcal (+/-3% of M) in four men who rested all day and lay down to sleep at night. Similar agreement was seen in one of the four who worked on a treadmill for 4 hr and stayed busy all day. but in another energy losses were 342 kcal greater than M (10% of M). When the experiments gave values for M minus the losses greater than +/-60 kcal, this is called "unmeasured energy". In further experiments, two subjects stayed awake for 24 hr, and their unmeasured energies were 279 and 393 kcal. The same two men, eating sparingly, also worked for 24 hr so as to double their resting metabolic expenditures; the unmeasured energies were even larger, 380 and 958 kcal. When they repeated the 24 hr of mild work, but ate nearly as much as they spent metabolically, one man was near energy balance, while the other showed an unmeasured energy of -363 kcal. Little heat storage was evident in these experiments; therefore, heat balance was present and energy balance should have been present. In the group of 13 experiments, it appeared that the greater the food deficit, the larger was the unmeasured energy (excess of metabolic expenditure over loss of energy).