Energy Expenditure Index Research Articles

Feeding, activity, and body temperature following 6-hydroxydopamine lesions in diabetes (db/db) mice.

Reductions in central catecholamines produced by intraventricular injections of 6-hydroxydopamine (6-OHDA) cause weight loss and decreased plasma glucose in diabetes (db/db) mice. The effects of this treatment were examined in short-term (64-day) and long-term (120-day) survival groups. Diabetes mice treated with 6-OHDA decreased food intake, lost weight, and maintained a lower weight than vehicle-treated controls until vehicle-treated animals began to enter the terminal stages of the syndrome, indicated by a loss of body weight. Diabetes mice given 6-OHDA lost weight despite reduced body temperatures and activity levels. Blood glucose levels were always lower in 6-OHDA than in ad lib fed vehicle-treated db/db mice. The 6-OHDA treatment also improved pancreatic islet granulation. Pair feeding vehicle-treated with 6-OHDA-treated db/db mice did not halt weight gain in the vehicle-treated group. However, measurement of carcass fat indicated similar losses in db/db-6-OHDA mice and vehicle-treated mice when the vehicle group was pair-fed with lean controls. Treatment with 6-OHDA produced long-term improvement in the diabetes syndrome, but the decreased body weight of the 6-OHDA-treated diabetes mice could not be completely accounted for by changes in food intake or measured indices of energy expenditure.

Heari rate as an index of energy expenditure in red squirrels ( Lamiasciurus hudsonicus)

Abstract o 1. Linear regressions of O2 consumption (O2) vs heart rate (fh) were observed in all exercising red squirrels (n=11) regardless of season, and in all winter-acclimatized (n=9) and some summeracclimatized (6 out of 11) resting red squirrels. 2. Mean correlation co-efficients were 0.94 during both rest (n=21) and exercise (n=11 animals). 3. Regressions of O2 vs fh varied within individuals from day to day, within individuals when different stimuli (cold vs exercise) ehcited increased VO2, and among individuals. 4. Mean absolute error in mean O2 of individuals over 8 or 12 hr, predicted from fh, under conditions similar to those in which the O2 vs fh regression was established varied from ±7.4 to ±20.3%, depending on the method whereby the predictive equation was established.

An equation for prediction of energy expenditure of walking and running.

An equation for prediction of energy expenditure of walking and running.

Energy production in cardiac isotonic contractions.

The energy output of rabbit papillary muscle is examined and it is shown that there is more energy liberated in an afterloaded isotonic contraction than in an "equivalent" isometric contraction. This statement holds true regardless of whether equivalence is based on the proposition that tension or the time integral of tension is the best index of muscle energy expenditure. Besides the external work performed there is additional heat production in isotonic contractions and this heat increases as the afterload is decreased. The additional heat is more evident when tension rather than the time integral of tension is made the determinant of energy expenditure. It is shown in single contractions that the rate of isotonic heat production, regardless of afterload size, never exceeds the heat rate recorded in an isometric contraction at the same initial length. Experiments reveal no simple linear correlation between isotonic energy output and contractile element work. Problems associated with the compartmentalization of the energy output of a contraction are discussed.

A comment on 'The relationship between energy expenditure and performance index in the task of shovelling sand' by C. H. Wyndham, et al.

A comment on 'The relationship between energy expenditure and performance index in the task of shovelling sand' by C. H. Wyndham, et al.

The relationship between energy expenditure and performance index in the task of shovelling sand.

An examination is made of the relationship between the energy expenditure in litres of oxygen consumed per minute, as measured by the physiologist, and the performance index, as assessed by the work-study engineer. The data used in the analysis were obtained from 16 Bantu labourers engaged in shovelling sand at four different rates of work into a mine car of 1 ton capacity. A close relationship between mean oxygen consumption and mean performance index over the range of work levels was found. A linear model appeared to describe the relationship between these two variables adequately. The particular linear relationship between the variables was, however, dependent on the observer, i.e. the lines for the two work-study engineers were different from each other. A performance index value of about 75 was found to be equivalent to an oxygen consumption of about 1-5 litres per minute. This is 50 per cent of the average Bantu mine labourer's maximum oxygen intake and, on physiological grounds, this is the rate of work which the Bantu labourer can maintain easily for a shift of 6-8 hours. However, it appears from the results of these preliminary studies that men working at a performance index value of 100 (i.e. well motivated in the work-study sense) are liable to work at a rate which is about 70 per cent of the maximum oxygen intake. This would be excessive for the average labourer. The existence of this close relationship is most encouraging and means that the work-study engineer would be able to relate his assessments to rates of energy expenditure and hence estimate the physical effort of men engaged on heavy manual labour.