Rate Of Metabolic Expenditure Research Articles

Office-Cycling: A Promising Way to Raise Pain Thresholds and Increase Metabolism with Minimal Compromising of Work Performance.

Aim Establishing the effects of low intensity cycling (LC), moderate intensity cycling (MC), and standing at a simulated office workstation on pain modulation, work performance, and metabolic expenditure. Methods36 healthy adults (21 females), mean age 26.8 (SD 7.6) years, partook in this randomized 3 × 3 crossover trial with 75 minutes of LC on 20% of maximum aerobic power (MAP) output, 30 minutes of MC on 50% of MAP, and standing 30 minutes with 48-hour wash-out periods. Outcome measures were pain modulation (pressure pain threshold (PPT) and thermal pain threshold)), work performance (transcription, mouse pointing, and cognitive performance), and metabolic expenditure. ResultsPPTs increased in all conditions. PPT trapezius showed the highest increase after LC, 39.3 kilopascals (kPa) (15.6; 78.6), compared to MC, 17.0 kPa (2.8; 49.9), and standing, 16.8 kPa (−5.6; 39.4), p = 0.015. Transcription was reduced during LC and MC. Mouse pointing precision was best during standing and worst and slowest during MC. Cognitive performance did not differ between conditions. Metabolic expenditure rates were 1.4 (1.3; 1.7), 3.3 (2.3; 3.7), and 7.5 (5.8; 8.7) kcal/minute during standing, LC, and MC, respectively (p < 0.001). Conclusions LC seems to be the preferred option; it raised PPTs, more than doubled metabolic expenditure, whilst minimally influencing work performance.

Feeding the injured pancreas

Feeding the injured pancreas

Body Size Evolution and the Concept of Alloenergetic Change

A theoretical mechanism of evolutionary body size change is proposed, based on the allometric scaling of energy intake and metabolic expenditure rates with body mass over ontogeny. Genetic or environmental changes that affect these allometries are hypothesized to incidentally change the balance of selective forces on adult body size. A new descriptive term, alloenergetic, relating to such changes is proposed. This new mechanism is termed the size-energy differential (SED) hypothesis. The SED mechanism is shown to be a potential factor in both evolutionary size increase and decrease. Random alloenergetic mutation under the SED hypothesis favors size increase on the average. The SED hypothesis predicts that adult mass, among species, should show a positive association with mass-specific net-production rates and mass-specific food conversion efficiencies during ontogeny. The SED hypothesis also generates realistic, positively skewed distributions of species body mass on a logarithmic scale, and may suggest a new approach to the explanation of "Cope's Rule" of evolutionary size increase. Problematical aspects of the model and its domain are discussed. The importance of both size-specific net production and size-specific mortality risk in determining the actual optimal adult size is emphasized.

Relationship between oxygen metabolism, aging and development

Abstract Evidence concerning the involvement of metabolic rate, prooxidants and antioxidants in processes of aging and development of animals is examined. Life span of poikilotherms and homeotherms is apparently dependent on a genetically-determined metabolic potential (i.e., total amount of energy expended during life per unit weight) and the rate of metabolic expenditure. Metabolic potential may vary in different species and under different environmental conditions. The relationship between metabolic potential, metabolic rate and duration of life is most demonstrable in organisms with a variable basal metabolic rate, such as poikilotherms and mammalian hibernators. Experimental regimes which reduce metabolic rate prolong life span and tend to retard the rate of age-related physiological and biochemical changes and vice versa. Effects of metabolic rate on aging may be mediated by oxygen free radicals. Antioxidant defenses tend to decline during aging, whereas, free radical induced damage seems to increase with age. Intracellular environment becomes progressively less reducing during the course of development and aging. We have postulated that such a shift in redox potential may play a role in the modulation of gene activity during development and aging.

Effect of temperature and different sex ratios on physical activity and life span in the adult housefly, musca domestica

The objective of this investigation was to further examine the relationship between physical activity and life span in the adult housefly. Levels of physical activity were experimentally varied by alterations in the ambient temperature and sex ratios of the populations. In agreement with previous studies, life span of the flies was significantly longer at 18°C than at 28%C. Female flies lived longer than males. Male flies in a population with a high male to female ratio lived a shorter period than their counterparts without any females. These variations in life span seem to be related to differences in the level of physical activity of the flies. The walking and flying activities of the various groups were measured separately by a radar-Doppler system. Walking activity increases about 15-fold, whereas flying activity increased more than 10 times between 15 and 24.5°C; thereafter there was a slight decline in both up to 28°C. Populations with female flies only exhibited lower levels of physical activity as compared to populations of males only. Populations with a high male to female ratio had the highest levels of walking and flying activities. The life spans of the flies were thus inversely related to the level of physical activity. Results of this study support the concept that the rate of metabolic expenditure has a strong influence on life span. The nature of the underlying mechanisms is, however, as yet obscure.

Relationship between physical activity and life span in the adult housefly, Musca domestica

The objective of this investigation was to explore the relationship between physical activity and life span in adult houseflies and to determine if the normal variations in the life span observed within a population correspond to the levels of physical activity of the individual flies. The levels of physical activity of male flies were experimentally manipulated by surgical removal of wings by varying the size of the housing containers. Walking and flying activities of the houseflies were measured, simultaneously, by a radar-Doppler device. Life spans were significantly prolonged following dealation and in response to conditions which decreased the level of physical activity. The median and the maximum life span of flies singly confined in small bottles, where they could walk but were unable to fly, was about 2.5 times longer than those housed in cages where flying was possible. The life spans were longer and levels of physical activity were lower in flies kept under conditions of solitary confinement as compared to those living in a group. Levels of physical activity of individual flies did, in general, correspond to the life span of the flies. Results of this study support the view that life span in the housefly is strongly influenced by the rate of metabolic expenditure.