Spontaneous Physical Activity Levels Research Articles

Influence of ageing and physical activity on vascular morphology in rat skeletal muscle

Key structural and functional properties of the skeletal muscle vasculature that underlie diminished vascular conductance with ageing remain obscure. The purpose of this investigation was to test the hypotheses that (1) reduced levels of spontaneous physical activity in old rats are associated with skeletal muscle vascular remodelling (e.g. arterial rarefaction), and (2) consequent to a vascular remodelling, calculated shear stress is maintained in feed arteries of aged muscle at levels commensurate with that in young. Activity during daily light and dark cycles (12-12 h) was measured at 30-s intervals for 2 weeks in young (6 months; n = 9) and old (24 months; n = 9) Fisher 344 rats via telemetry. Subsequently, the gastrocnemius complex and soleus muscles were excised and all feed arteries were counted, isolated, cannulated and maximally dilated for measurement of luminal diameter. Resting blood flow was also measured to estimate vessel wall shear-stress in the feed arteries perforating the soleus and gastrocnemius muscles. Overall, young rats were approximately 1.6 times more active during dark periods and approximately 4 times more active during light periods than old rats. In addition, young rats had approximately one additional feed artery perforating both the soleus (young, 3.3 +/- 0.2; old, 2.6 +/- 0.2 vessels; P < 0.05) and gastrocnemius (young, 8.8 +/- 0.1; old, 7.5 +/- 0.2 vessels, P < 0.05) muscles compared with old rats. However, average vessel wall shear stress at rest was similar between young and old rats (soleus: Y, 65 +/- 5; O, 64 +/- 5 dynes cm(-2); gastrocnemius: Y, 329 +/- 22; O, 327 +/- 27 dynes cm(-2)) resulting from a larger vessel diameter in arteries from old rats. In conclusion, lower activity levels of old rats likely contribute to resistance artery rarefaction and, consequently, this provides a plausible mechanism for the altered blood flow patterns observed during exercise in aged skeletal muscle.

A Profile of Daily Activity in Chronic Obstructive Pulmonary Disease

Little information exists about the pattern of daily activity in patients with chronic obstructive pulmonary disease (COPD), especially in those who are on long-term oxygen therapy (LTOT). The aim of this study was to explore the regular level of domestic physical activity in patients with COPD and to explore differences in activity in those on LTOT. Daily activity was recorded using an activity monitor for 7 consecutive days in 4 groups. Group 1 had severe COPD (FEV1 0.66 [0.42] L) receiving LTOT (n = 9). Group 2 had severe COPD (FEV1 1.07 [0.43] L) and had full knowledge of the activity monitor and the purpose of the study (n = 10). Group 3 had severe COPD (FEV1 1.16 [0.27] L) but were unaware of the precise nature of the study (n = 10). Group 4 (n = 10) were the healthy control group. Participants also completed health status questionnaires. There were statistically significant differences in the level of daily activity between all groups (P < .001) except between groups 2 and 3. There were no significant differences between days within groups. The activity counts compared to the healthy groups were reduced by 49% in groups 2 and 3 and by 79% in those on LTOT. Patients with COPD demonstrate reduced levels of spontaneous physical activity compared with healthy controls. Furthermore, patients receiving LTOT have an even lower level of domestic activity compared with that of those not on LTOT but with COPD of similar severity.

Obesity and the Neuroendocrine Control of Energy Homeostasis: The Role of Spontaneous Locomotor Activity

Obesity represents one of the most urgent global health threats as well as one of the leading causes of death throughout industrialized nations. Efficacious and safe therapies remain at large. Attempts to decrease fat mass via pharmacological reduction of energy intake have had limited potency or intolerable side effects. Increasingly widespread sedentary lifestyle is often cited as a major contributor to the increasing prevalence of obesity. Moreover, low levels of spontaneous physical activity (SPA) are a major predictor of fat mass accumulation during overfeeding in humans, pointing to a substantial role for SPA in the control of energy balance. Despite this, very little is known about the molecular mechanisms by which SPA is regulated. The overview will attempt to summarize available information on neuroendocrine factors regulating SPA.

Subnormal energy expenditure: a putative causal factor in the weight gain induced by treatment of hyperthyroidism

To examine the causes of weight gain occurring as an adverse effect of treatment of hyperthyroidism. We measured 24-h energy expenditure (EE), body composition and spontaneous physical activity (SPA) in eight patients before and 1 year after treatment of hyperthyroidism was initiated, and eight controls. One year after initiation of treatment thyrotropin was normalized, thyroid hormones had fallen to the lower end of the reference range and fat mass had increased by 3.5 kg (p < 0.001). Twenty-four hour EE adjusted for fat-free mass (FFM) was 15% higher in hyperthyroid patients before treatment than in controls (p = 0.003), and treatment decreased 24-h EE by 1.9 MJ/day (p = 0.001). After treatment, 24-h EE, adjusted for FFM, was similar to the controls. Multiple regression analyses showed that the suppressed EE could partly be attributed to an iatrogenic suppression of thyroid hormones, resulting in lower sleeping EE. Twenty-four hour SPA was normal in the hyperthyroid state, but decreased after treatment by 21% (p = 0.045), to a level not significantly different, but still below that of the controls. The study suggests that weight gain during treatment of hyperthyroidism might be due to subnormal levels of EE and SPA caused by a suppression of the thyroid hormone to a level in the lower end of the normal range.

Aromatase-deficient (ArKO) mice accumulate excess adipose tissue

Aromatase is the enzyme which catalyses the conversion of C 19 steroids into C 18 estrogens. We have generated a mouse model wherein the Cyp19 gene, which encodes aromatase, has been disrupted, and hence, the aromatase knockout (ArKO) mouse cannot synthesise endogenous estrogens. We examined the consequences of estrogen deficiency on accumulation of adipose depots in male and female ArKO mice, observing that these animals progressively accrue significantly more intra-abdominal adipose tissue than their wildtype (WT) litter mates, reflected in increased adipocyte volume and number. This increased adiposity was not due to hyperphagia or reduced resting energy expenditure, but was associated with reduced spontaneous physical activity levels, reduced glucose oxidation, and a decrease in lean body mass. Elevated circulating levels of leptin and cholesterol were present in 1-year-old ArKO mice compared to WT controls, as were elevated insulin levels, although blood glucose was unchanged. Associated with these changes, the livers of ArKO animals were characterised by a striking accumulation of lipid droplets. Our findings demonstrate an important role for estrogen in the maintenance of lipid homeostasis in both males and females.

Exercise prescription for the elderly: current recommendations.

The benefits for elderly individuals of regular participation in both cardiovascular and resistance-training programmes are great. Health benefits include a significant reduction in risk of coronary heart disease, diabetes mellitus and insulin resistance, hypertension and obesity as well as improvements in bone density, muscle mass, arterial compliance and energy metabolism. Additionally, increases in cardiovascular fitness (maximal oxygen consumption and endurance), muscle strength and overall functional capacity are forthcoming allowing elderly individuals to maintain their independence, increase levels of spontaneous physical activity and freely participate in activities associated with daily living. Taken together, these benefits associated with involvement in regular exercise can significantly improve the quality of life in elderly populations. It is noteworthy that the quality and quantity of exercise necessary to elicit important health benefits will differ from that needed to produce significant gains in fitness. This review describes the current recommendations for exercise prescriptions for the elderly for both cardiovascular and strength/resistance-training programmes. However, it must be noted that the benefits described are of little value if elderly individuals do not become involved in regular exercise regimens. Consequently, the major challenges facing healthcare professionals today concern: (i) the implementation of educational programmes designed to inform elderly individuals of the health and functional benefits associated with regular physical activity as well as how safe and effective such programmes can be; and (ii) design interventions that will both increase involvement in regular exercise as well as improve adherence and compliance to such programmes.

Role of substrate utilization and thermogenesis on body-weight control with particular reference to alcohol.

Alcohol (ethanol; EtOH) provides fuel energy to the body (29.7 kJ (7. 1 kcal)/g, 23.4 kJ (5.6 kcal)/ml), as do other macronutrients, but no associated essential nutrients. The thermogenic effect of EtOH (on average 15 % of its metabolizable value) is much greater than that of the main substrates utilized by the body, i.e. fat and carbohydrates (CHO), suggesting a lower net efficiency of energy utilization for EtOH than for fat and CHO. EtOH cannot be stored in the body and is toxic, so that there is an obligatory continuous oxidation of EtOH and it becomes the priority fuel to be metabolized. In contrast to CHO, its rate of oxidation does not depend on the dose ingested. As with CHO intake, it engenders a shift in postprandial substrate utilization (decrease in fat oxidation), but by a non-insulin-mediated mechanism. A limited amount of EtOH can be converted to fatty acids by hepatic de novo lipogenesis (as occurs with high levels of CHO feeding) from acetate production, which inhibits lipolysis in peripheral tissues. There is no evidence that EtOH consumed under normoenergetic conditions (i.e. isoenergetically replacing CHO or fat) leads to greater body fat storage than fat or CHO. However, there is still a lack of experimental studies on the influence of EtOH on the level of spontaneous physical activity in man. This effect may well depend on the dose of EtOH consumed as well as other intrinsic factors.

Energy balance and weight regulation: genetics versus environment.

The prevalence of obesity is reaching epidemic proportions in many industrialized countries. There is growing evidence that, even if the trigger of this epidemic is found in changes in the environment, genes are interacting with the environment to cause weight gain. Studies of twins reared apart indicate that approximately two-thirds of the variability in BMI is attributed to genetic factors. From prospective studies in Pima Indians we can ascribe 12% of the variability in BMI to metabolic rate, 5% to fat oxidation, and another probable 10% to the level of spontaneous physical activity. These data indicate that at least 40% of the variability in BMI is related to genetic factors involved in the regulation of food intake and/or volitional activity. This indicates that the most likely successful therapy for obesity may target pathways of the regulation of food intake. Similarly, an environment favouring engagement in physical activity should be promoted.

Leptin responses to overfeeding: relationship with body fat and nonexercise activity thermogenesis.

Administration of leptin to rodents results in weight loss through decreased food intake and increased energy expenditure that occurs in part through increased spontaneous activity. In humans, low levels of spontaneous physical activity and below normal plasma leptin concentrations predict subsequent excess weight gain. We recently found that failure to increase nonexercise activity thermogenesis (NEAT) with overfeeding results in greater fat gain in humans, and subsequently evaluated whether changes in leptin are related to NEAT activation. We measured plasma leptin concentrations and adipose tissue leptin messenger ribonucleic acid together with the components of energy expenditure in 16 nonobese humans before and after overfeeding to assess the relationship between leptin responses to overfeeding and the changes in NEAT. Adipocyte leptin expression was up-regulated with overfeeding, and leptin concentrations increased. Leptin concentrations correlated with body fat before and after overfeeding. Changes in leptin with overfeeding were strongly related to changes in body fat, but not to changes in NEAT. Changes in NEAT correlated inversely with fat gain. It is, therefore, unlikely that leptin mediates activation of NEAT with overfeeding in nonobese humans; rather, leptin directly reflects body fat mass and fat mass gain.

Metabolic differences and the development of obesity

Studies, such as those on Pima Indians, have shown that metabolic factors are involved in the development of obesity and that being overweight is not simply a result of “sloth and gluttony.” However, the environment also affects the development of obesity. Among individuals in a given environment, the variability in body size is influenced by genetically determined responses to that environment. People with a low metabolic rate (adjusted for body size and composition) are prone to weight gain, whereas those with a high level of spontaneous physical activity are less likely to become obese. Similarly, individuals with a high 24-hour respiratory quotient (RQ) are more likely to gain weight than those with a low RQ. Insulin sensitivity (not insulin resistance) is another metabolic predictor of obesity. Genetic linkage studies suggest a number of genes are linked to the development of obesity. By sibling-pair linkage analysis, tumor necrosis factor-alpha (TNF-α) was found to be linked to the percentage of body fat, and other studies have shown that fat cell production of TNF-α is greater in obese individuals.

Thermic effect of food in humans: methods and results from use of a respiratory chamber.

During the past two decades, many investigators have measured the thermic effect of food (TEF) in humans and have speculated on its role in the development of obesity. In this study we compared different ways of computing TEF from daily energy expenditure measurements in a respiratory chamber, evaluated the determinants of TEF, and more importantly assessed for the first time the relation between TEF and change in body weight. In 471 subjects, TEF was 1697 +/- 857 kJ/d (mean +/- SD), ie, 18 +/- 9% of energy intake. In 114 subjects studied more than once, intraindividual TEF variability was very high (CV = 48%). TEF correlated positively with the level of spontaneous physical activity (SPA) and negatively with fasting plasma glucose and insulin concentrations. TEF correlated inversely with age (males only) and body weight, percent body fat, and waist-to-hip ratio (females only). The level of SPA and fasting plasma glucose concentration were the only significant determinants of TEF, explaining 15% of its variance. In 137 subjects in whom body weight was measured > or = 6 mo after TEF measurement (mean follow-up duration of 2.9 +/- 1.7 y), a low TEF was not predictive of body weight gain. We conclude that, despite the low reproducibility of TEF from use of a respiratory chamber, data in a large number of subjects suggest that TEF is increased by higher SPAs and that insulin resistance is associated with a low TEF. More important, longitudinal data indicate that the variability in TEF is not associated with changes in body weight.

Thermic effect of food in humans: methods and results from use of a respiratory chamber

During the past two decades, many investigators have measured the thermic effect of food (TEF) in humans and have speculated on its role in the development of obesity. In this study we compared different ways of computing TEF from daily energy expenditure measurements in a respiratory chamber, evaluated the determinants of TEF, and more importantly assessed for the first time the relation between TEF and change in body weight. In 471 subjects, TEF was 1697 +/- 857 kJ/d (mean +/- SD), ie, 18 +/- 9% of energy intake. In 114 subjects studied more than once, intraindividual TEF variability was very high (CV = 48%). TEF correlated positively with the level of spontaneous physical activity (SPA) and negatively with fasting plasma glucose and insulin concentrations. TEF correlated inversely with age (males only) and body weight, percent body fat, and waist-to-hip ratio (females only). The level of SPA and fasting plasma glucose concentration were the only significant determinants of TEF, explaining 15% of its variance. In 137 subjects in whom body weight was measured ≥ or = 6 mo after TEF measurement (mean follow-up duration of 2.9 +/- 1.7 y), a low TEF was not predictive of body weight gain. We conclude that, despite the low reproducibility of TEF from use of a respiratory chamber, data in a large number of subjects suggest that TEF is increased by higher SPAs and that insulin resistance is associated with a low TEF. More important, longitudinal data indicate that the variability in TEF is not associated with changes in body weight.

Exercise Training and Nutritional Supplementation for Physical Frailty in Very Elderly People

Although disuse of skeletal muscle and undernutrition are often cited as potentially reversible causes of frailty in elderly people, the efficacy of interventions targeted specifically at these deficits has not been carefully studied. We conducted a randomized, placebo-controlled trial comparing progressive resistance exercise training, multinutrient supplementation, both interventions, and neither in 100 frail nursing home residents over a 10-week period. The mean (+/- SE) age of the 63 women and 37 men enrolled in the study was 87.1 +/- 0.6 years (range, 72 to 98); 94 percent of the subjects completed the study. Muscle strength increased by 113 +/- 8 percent in the subjects who underwent exercise training, as compared with 3 +/- 9 percent in the nonexercising subjects (P < 0.001). Gait velocity increased by 11.8 +/- 3.8 percent in the exercisers but declined by 1.0 +/- 3.8 percent in the nonexercisers (P = 0.02). Stair-climbing power also improved in the exercisers as compared with the nonexercisers (by 28.4 +/- 6.6 percent vs. 3.6 +/- 6.7 percent, P = 0.01), as did the level of spontaneous physical activity. Cross-sectional thigh-muscle area increased by 2.7 +/- 1.8 percent in the exercisers but declined by 1.8 +/- 2.0 percent in the nonexercisers (P = 0.11). The nutritional supplement had no effect on any primary outcome measure. Total energy intake was significantly increased only in the exercising subjects who also received nutritional supplementation. High-intensity resistance exercise training is a feasible and effective means of counteracting muscle weakness and physical frailty in very elderly people. In contrast, multi-nutrient supplementation without concomitant exercise does not reduce muscle weakness or physical frailty.

Norepinephrine turnover and energy expenditure in Pima Indian and white men

There is growing evidence of the involvement of sympathetic nervous system (SNS) activity in determining metabolic rate. Whole-body plasma norepinephrine turnover and its relationship to resting metabolic rate (RMR) and 24-hour energy expenditure (24EE) were compared in 14 Pima Indian men (25 ± 4 years, 96 ± 33 kg, 25% ± 9% fat) and nine white men (25 ± 3 years, 88 ± 43 kg, 17% ± 13% fat). Plasma norepinephrine turnover rate correlated strongly with body surface area ( r = .76 and .54 for clearance and appearance, respectively) and fat-free mass ( r = .74 and .52, respectively). However, independent of body size, there was no difference in either norepinephrine clearance or appearance rates between Pima Indian and white men. Norepinephrine appearance rate correlated positively with absolute values of 24EE and RMR, but not when adjusted for differences in body surface area or fat-free mass. However, norepinephrine appearance rate adjusted for differences in body size correlated with spontaneous physical activity. The results indicate that Pima Indian and white men have similar plasma norepinephrine appearance rates, but Pima Indians tend to be more resistant β-adrenergic stimulation. Although energy expenditure and SNS activity were not directly related, a higher SNS tone may either promote or reflect elevated levels of spontaneous physical activity and therefore influence both energy balance and body composition.

Effect of endurance training on sedentary energy expenditure measured in a respiratory chamber

The effect of endurance training on 24-h energy expenditure (EE), basal metabolic rate (BMR), sleeping metabolic rate (SMR), and the thermic effect of food (TEF) was assessed in a respiratory chamber where only spontaneous physical activity (SPA) was allowed. Results from 20 highly trained male endurance athletes (25 +/- 5 yr, 178 +/- 7 cm, 70 +/- 8 kg body wt, 64 +/- 7 kg fat-free mass) were compared with those of 43 untrained males who were matched for age (28 +/- 6 yr), height (175 +/- 5 cm), weight (73 +/- 13 kg), and fat-free mass (62 +/- 8 kg). Subjects were admitted to a metabolic ward, fed a weight-maintenance diet, and refrained from physical activity for at least 2 days before measurements. No significant differences were found with respect to 24-h EE (2,126 +/- 186 vs. 2,154 +/- 245 kcal), BMR (1,808 +/- 342 vs. 1,709 +/- 329 kcal), SMR (1,523 +/- 120 vs. 1,555 +/- 188 kcal), or TEF (24.9 +/- 9.2 vs. 21.3 +/- 6.7% of ingested calories; these values included the energy cost of arousal) between trained and untrained subjects, respectively, before or after adjusting for differences in body composition. Neither the 24-h respiratory quotient nor the level of SPA differed between the two groups. No relationship was found between maximal aerobic capacity and metabolic rate adjusted for differences in fat-free mass and fat mass. These results do not support an effect of fitness level on EE measured under sedentary conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Energy expenditure during normo- and overfeeding in peripubertal children of lean and obese Pima Indians.

We investigated the hypothesis that peripubertal children born to obese parents have a lower 24-h energy expenditure during "weight maintenance" and/or in response to overfeeding when compared with children born to normal-weight parents. Sixteen Southwestern American Indians (12.4 +/- 1.4 yr, 55.5 +/- 14.1 kg, 30 +/- 8% body fat), eight offspring from obese parents [body mass index (BMI) = 40 +/- 6 kg/m2], and eight offspring from thin parents (BMI = 24 +/- 3 kg/m2) were admitted for 8 days to our metabolic ward. The 24-h energy expenditure was measured under eucaloric conditions and on the 3rd day of progressive overfeeding of a mixed diet, i.e., 150, 200, and 200% of weight maintenance on day 1, 2, and 3 of overfeeding. At base line, offspring of obese parents were heavier (64 +/- 15 vs. 47 +/- 6 kg, P less than 0.05) and tended to be fatter (34 +/- 8 vs. 26 +/- 9% body fat, P = 0.07), with a higher absolute fat mass (22 +/- 9 vs. 13 +/- 4 kg body fat, P less than 0.05) when compared with offspring of thin parents. During both normo- and over-feeding, the larger part of the variance in 24-h energy expenditure in the conditions of a respiratory chamber was accounted for by differences in fat-free body mass (54 and 68%, respectively), whereas differences in the level of spontaneous physical activity accounted for another 19 and 21%.(ABSTRACT TRUNCATED AT 250 WORDS)

Impact of Early Nutrition on Later Development of Spontaneous Physical Activity and Lipid Metabolism

Male rats suckled in large litters (more than 12 pups, group A) had significantly higher levels of spontaneous physical activity and temporarily increased food intake (g/100 g body weight) than male rats from small litters (less than 6 pups, group B). Females did not differ. Epididymal fat pads were significantly lighter in males in group A. The concentration of total lipids in the small intestine was significantly higher in females from group A, and the synthesis of lipids was higher in the animals of both sexes from group A. The synthesis of fatty acids in the intestines was significantly greater in both males and females from group A. Cholesterol concentration in the liver and carcass was the same in all groups. Cholesterogenesis was higher in the liver only in males from group B, and in the carcass in the animals of both sexes from group B.

Dissociation Between Dietary Effects on Plasma Lipid Concentration and on Plasma Lipoprotein Distribution in Selected Rats

The influence of two types of diet on plasma total choles terol and triglycA©ride concentration, and on the lipoprotein distribution was studied in rats with genetically different levels of spontaneous running activity. Genetically active and passive rats of both sexes were fed an open formula cereal based stock diet or a purified diet containing sucrose (47% of calories), coconut fat (35% of calories), and casein (18% of calories) from the age of 3 to 8 months, during which time blood samples were taken three times. In genetically active female rats fed the purified diet the plasma total cholesterol and triglycA©rideconcentrations were higher than in the corresponding groups of rats fed stock diet. In genetically passive rats, on the other hand, no difference in plasma total cholesterol and triglycA©ride concentration between rats fed stock diet and those fed purified diet was observed. The plasma lipid concentration was not related to the level of spontaneous physical activity or to the body weight. The pattern of lipoprotein distribution was very similar in all groups fed the same diet (i.e., actives and passives of each sex). In groups fed the puri fied diet a slight decrease in percentage of the pre-beta and beta fractions, a pronounced increase in a diffuse pre-alpha fraction and a decrease in the alpha fraction was observed as compared with groups fed stock diet. The data for passive rats suggest that a given diet may have an appreciable influence on the lipoprotein distribution without affecting the concentra tion of total cholesterol and triglycA©rides in plasma. J. Nutr. 108: 1823- 1829, 1978.