The effects of either 12-wk of high-intensity endurance or resistance training on resting metabolic rate (RMR) were investigated in 47 males aged 18-35 y. Subjects were randomly assigned to either a control (C), resistance- trained (RT) or endurance-trained (ET) group. After training both exercise groups showed significant declines in relative body fat either by reducing their total fat weight and maintaining fat-free weight (ET) or by reducing their total fat weight and increasing fat-free weight (RT). RMR did not significantly change after either training regimen although a small decline in energy intake was observed along with an increase in energy expenditure [ET, 2.721 MJ (650 kcal) per training day]. These results suggest that both endurance and resistance training may help to prevent an attenuation in RMR normally observed during extended periods of negative energy balance (energy intake < expenditure) by either preserving or increasing a person's fat-free weight.

A cross-sectional study was designed to determine the relationship between aerobic fitness and resting metabolic rate (RMR) in 69 males exhibiting a wide range of aerobic fitness levels (V̇O2max = 32.8-78.1 mL · kg-1 · min-1). The results of this study indicated that RMR was not significantly different between trained and untrained individuals when expressed in kJ · kg fat-free weight-1 · hr-1 or using an ANCOVA with fat-free weight as the covariate and RMR as the dependent variable (F ratio = 0.353, P < 0.70). In addition, this study also failed to support a previously suggested hypothesis that an elevated RMR may only be observed in those individuals exhibiting both high V̇O2max values and currently training a minimum of 12- 16 h/wk. Thus, the results of this study strongly suggest that RMR is independent of both a person's current aerobic level and training status.

No description available.

Resting metabolic rate (RMR) represents the lowest level of aerobic metabolism in a resting individual. By contrast, maximal metabolic rate (MMR) reflects the upper limit of aerobic metabolism achieved during intensive exercise. As RMR and MMR define the boundaries of the possible levels of metabolism expressed by a normothermic individual, a key question is whether RMR and MMR are correlated. To evaluate the relationship between RMR and MMR, I took repeated paired measurements of RMR and MMR on 165 white-footed mice (Peromyscus leucopus) during the summer of 2018. Repeatability (R±se) was significant for both RMR and MMR (RRMR=0.15±0.07 and RMMR=0.27±0.12). At the residual level (within-individual), RMR and MMR were significantly and positively correlated (re=0.20, 95% confidence intervals: 0.04, 0.34). Such a positive residual correlation could be result of correlated phenotypic plasticity. By contrast, RMR and MMR were significantly and negatively correlated at the among-individual level (rind=-0.87, 95% confidence intervals: -0.99, -0.28). The negative among-individual correlation suggests there are trade-offs between the maintenance and active components of the energy budget (allocation model). Future research should investigate the relationship between RMR and other energetically expensive behaviours and activities to understand how energy is allocated among individuals.

No description available.

ABSTRACT Phenotypic flexibility in basal metabolic rate (BMR) in response to short-term thermal acclimation was assessed in the Laughing Dove (Streptopelia senegalensis), a common resident bird species distributed throughout most of southern Africa. I hypothesised that S. senegalensis would display flexibility in BMR over short time scales and that this flexibility would be reversible. Additionally, I hypothesised BMR to be repeatable, and that changes in BMR would be correlated with changes in organ mass. I tested these hypotheses by measuring BMR in three groups of 10 birds before and after a short-term (21 day) thermal acclimation period to one of three air temperatures (10o, 22o & 35oC). After acclimation the three temperature groups were randomly divided and reverseacclimated for another 21 days to one of the two thermal environments not yet experienced. After this reverse-acclimation period BMR was measured again. The dry masses of the stomach, kidney, heart, intestines, liver and pectoral muscles of acclimated birds were used to determine possible mechanistic correlates of BMR adjustments. Additionally, by monitoring BMR every 4-6 days during cold (10oC) and heat (35oC) acclimation I was able to assess the temporal dynamics of adjustments in BMR in response to short-term thermal acclimation. BMR was both flexible and reversible in S. senegalensis as a consistent relationship between BMR and acclimation air temperature was observed after acclimation and reverse-acclimation. BMR increased with decreasing acclimation temperature. Furthermore, a significant proportion (25%) of the observed variation in BMR was repeatable in the 22oC group in spite of the change in BMR induced by thermal acclimation. The mechanistic correlate of BMR adjustment in S. senegalensis appears to be metabolic intensity and not organ size, as the only organ to show a significant increase in size was the intestine of the acclimated 10oC group, which was significantly heavier than the intestine of the 22oC group. BMR also decreases in response to the reduction of flight and/or exercise. Since this reduction was not accompanied by a correlated change in organ mass or body mass, the reduction in BMR as a response to captivity appears to be linked to metabolic intensity of the organs and skeletal muscles. In S. senegalensis adjustments in BMR occur during the first 30 days of captivity and thermal acclimation. The response in BMR to acclimation temperature is clearly evident as BMR of the heat-acclimated group was significantly lower than the coldacclimated group after 21 days. During the response period, which lasts approximately 30 days, BMR adjusts as a mechanism to offset the costs of thermoregulation and habituation to captivity while other metabolic parameters such as body mass, body temperature, and minimum wet thermal conductance adjust to captivity and the thermal environment. After 30 days BMR of the cold and heat-acclimated groups converge on 0.68W, indicating that once the associated metabolic parameters adjust and stabilize in response to the thermal environment, BMR continues to adjust to captivity.

Anfíbios tem a habilidade de manifestar febre comportamental em ambientes heterotermais durante infecção a um custo metabólico associado à elevação da temperatura corpórea e à ativação do sistema imune. Apesar do custo metabólico, a temperatura corpórea febril otimiza a resposta imune no combate à infecção e aumenta as chances de sobrevivência do indivíduo. Contudo, devido à limitada capacidade de termorregular, os anfíbios enfrentam variações diárias e sazonais na temperatura corpórea e na resposta metabólica de reação à infecção. O nosso objetivo foi medir a variação da resposta metabólica à infecção dentro da variação de temperaturas ecológicas relevantes do sapo Cururu. Testamos a hipótese de que a infecção aumenta as taxas metabólicas do sapo Cururu, mas o custo energético da resposta imune deve ser menor na temperatura febril dos sapos infectados. Para testarmos as hipóteses, nós medimos a temperatura operacional dos sapos no campo, a preferencia termal dos sapos hígidos e a temperatura preferencial dos sapos infectados. Depois, medimos a taxa metabólica e a resposta metabólica dos sapos antes e depois da infecção por LPS nessas temperaturas. Nossos resultados mostraram que as temperaturas ecológicas relevantes dos sapos variaram entre 17°C e 26°C. A temperatura influenciou a taxa metabólica dos sapos, mas só na temperatura preferencial dos sapos hígidos houve custo metabólico associado à infecção. Contudo, na temperatura corpórea dos sapos infectados a resposta metabólica de reação à infecção foi menor, indicando que o controle regulado no ponto de ajustes \"set-point\" da temperatura corpórea durante a infecção coevoluiu com um custo energético otimizado da resposta imune / Anphibians have the ability of manifested behavioral fever in heterothermal environments during infection with a metabolic cost associated to elevated body temperature set-point and due to activation of immune system. Despite the metabolic cost, fever body temperature optimizes immune response to combat infection and increase the survival of the host. However, because of the limited capacity for thermoregulation, amphibians can confront daily and seasonal variation in body temperature and in the metabolic response of reaction to combat infection. So, we measured the variation in metabolic response of reaction to infection at ecology relevant body temperature range in Cururu toads. We hypothesized that infection increases metabolic rates of the Cururu toads due to the activation of the immune system at different temperatures, but the energetic cost of immune response is lower at preferred body temperature of infected toads (behavioral fever). To test these hypotheses we measured the operative body temperature in the field, the preferred body temperature of higid toads, and the preferred body temperature of infected toads. After, we measured metabolic rate and metabolic response of the toads before and after injection of LPS at these temperatures. Our results showed that the ecology relevant temperature range of Cururu toads (R. icterica) varies between 17°C and 26°C, respectively, at operative temperature and at preferred body temperature in infected toads when exposed to heterothermal environment. The temperature had the major impact on metabolic rate of the toads during infection. But, at fever body temperature toads decrease the metabolic response of reaction to infection, indicating that the regulated control of body temperature set-point during infection coevolved with an optimized energetic cost of immune response

Anfíbios tem a habilidade de manifestar febre comportamental em ambientes heterotermais durante infecção a um custo metabólico associado à elevação da temperatura corpórea e à ativação do sistema imune. Apesar do custo metabólico, a temperatura corpórea febril otimiza a resposta imune no combate à infecção e aumenta as chances de sobrevivência do indivíduo. Contudo, devido à limitada capacidade de termorregular, os anfíbios enfrentam variações diárias e sazonais na temperatura corpórea e na resposta metabólica de reação à infecção. O nosso objetivo foi medir a variação da resposta metabólica à infecção dentro da variação de temperaturas ecológicas relevantes do sapo Cururu. Testamos a hipótese de que a infecção aumenta as taxas metabólicas do sapo Cururu, mas o custo energético da resposta imune deve ser menor na temperatura febril dos sapos infectados. Para testarmos as hipóteses, nós medimos a temperatura operacional dos sapos no campo, a preferencia termal dos sapos hígidos e a temperatura preferencial dos sapos infectados. Depois, medimos a taxa metabólica e a resposta metabólica dos sapos antes e depois da infecção por LPS nessas temperaturas. Nossos resultados mostraram que as temperaturas ecológicas relevantes dos sapos variaram entre 17°C e 26°C. A temperatura influenciou a taxa metabólica dos sapos, mas só na temperatura preferencial dos sapos hígidos houve custo metabólico associado à infecção. Contudo, na temperatura corpórea dos sapos infectados a resposta metabólica de reação à infecção foi menor, indicando que o controle regulado no ponto de ajustes \"set-point\" da temperatura corpórea durante a infecção coevoluiu com um custo energético otimizado da resposta imune / Anphibians have the ability of manifested behavioral fever in heterothermal environments during infection with a metabolic cost associated to elevated body temperature set-point and due to activation of immune system. Despite the metabolic cost, fever body temperature optimizes immune response to combat infection and increase the survival of the host. However, because of the limited capacity for thermoregulation, amphibians can confront daily and seasonal variation in body temperature and in the metabolic response of reaction to combat infection. So, we measured the variation in metabolic response of reaction to infection at ecology relevant body temperature range in Cururu toads. We hypothesized that infection increases metabolic rates of the Cururu toads due to the activation of the immune system at different temperatures, but the energetic cost of immune response is lower at preferred body temperature of infected toads (behavioral fever). To test these hypotheses we measured the operative body temperature in the field, the preferred body temperature of higid toads, and the preferred body temperature of infected toads. After, we measured metabolic rate and metabolic response of the toads before and after injection of LPS at these temperatures. Our results showed that the ecology relevant temperature range of Cururu toads (R. icterica) varies between 17°C and 26°C, respectively, at operative temperature and at preferred body temperature in infected toads when exposed to heterothermal environment. The temperature had the major impact on metabolic rate of the toads during infection. But, at fever body temperature toads decrease the metabolic response of reaction to infection, indicating that the regulated control of body temperature set-point during infection coevolved with an optimized energetic cost of immune response

The bluefin tuna have a variety of distinctive anatomical and physiological adaptations that enhance performance. However, our understanding of bluefin tuna physiology is limited by the logistical difficulties of studying these large pelagic fish. This thesis examines some aspects of the metabolic physiology of the southern bluefin tuna. It provides insight into the high-performance, high-energy demand physiology of bluefin. It also examines the metabolic physiology of the mulloway, another important aquaculture species for which physiological information is currently limited. 1. Routine metabolic rate (RMR) of southern bluefin tuna (SBT) (Thunnus maccoyii), the largest tuna specimens studied so far (body mass = 19.6 kg (± 1.9 SE)) was measured in a large (250,000 l) flexible polypropylene respirometer “mesocosm respirometer”. Mean mass-specific RMR was 460 mg kg⁻¹ h⁻¹ (± 34.9) at a mean water temperature of 19°C. When total RMR is added to published values of other tuna species at equivalent swimming speeds, there is a strong allometeric relationship with body mass (654 • Mb ⁰·⁹ ⁵, R ² = 0.97). This demonstrates that interspecific RMR of tuna scale with respect to body mass similar to that of other teleosts, but is approximately 5-fold higher than the standard metabolic rate (SMR) of other active teleost species. 2. This study reports on the first measurements of the metabolic cost of food digestion and assimilation (specific dynamic action, SDA) of a tuna species. Oxygen consumption (MO₂) and swimming velocity of southern bluefin tuna (SBT) (Thunnus maccoyii) were elevated for periods between 20-45 h (longest for the largest rations) post-ingestion of sardines (Sardinops sagax). It is suggested that the purpose of increased swimming velocity was to increase ventilation volume as a response to the enhanced metabolic demand associated with SDA. The magnitude of SDA as a proportion of gross energy ingested (SDA coefficient) averaged 35 ± 2.2 %. This demonstrates that the absolute energetic cost of SDA in SBT is approximately double that recorded in other teleost species. 3. This study examines the effects of sardines (Sardinops sagax) with high- (12.9%) or low- (1.8-4.0%) lipid level on specific dynamic action (SDA) and swimming velocity of southern bluefin tuna (SBT) (Thunnus maccoyii). Fish swam faster during the SDA period with the increase in velocity being greatest for the fish that ingested the high-lipid sardine. Magnitude of SDA was also greater for fish that ingested the high-lipid sardines. However, the energetic cost of SDA as a proportion of ingested energy was not significantly different between fish that ingested the high- (34.3 ± 2.4%) and low-lipid sardines (31.5 ± 2.9%). These results confirm that the high energetic cost of SDA is ecologically relevant. 4. In this study the metabolic and behavioural responses of both fasted and postprandial southern bluefin tuna (Thunnus maccoyii, SBT) to low dissolved oxygen (DO) was examined. In moderate hypoxia (4.44 and 3.23 mg l⁻¹), swimming velocity (U) and routine metabolic rate (RMR) of fasted fish was mildly enhanced. At 2.49 mg l⁻¹, U increase to over double in the normoxic speed, possibly as an escape response. At 1.57 mg l⁻¹, both U and RMR were suppressed and SBT failed to survive the entire 20 h exposure period. This reveals that SBT are remarkably well adapted to low DO. Feeding did not greatly influence their hypoxia tolerance. In a subsequent experiment there were no significant differences in U, RMR and gastric evacuation rates of postprandial SBT in hypoxia (2.84 mg l⁻¹) compared to those in normoxia (7.55 mg l-¹). 5. In this study, 768 h of simultaneous recordings of metabolic rate (MR, = heat production) and visceral temperature were made in both fasted and postprandial southern bluefin tuna (SBT, Thunnus maccoyii) of two sizes (~10 and 20 kg) and at two water temperatures (~19 and 16°C). Duration and magnitude of specific dynamic action (SDA) were strongly related to duration and magnitude of postprandial visceral warming providing the first empirical evidence of a link between SDA and postprandial visceral warming. Visceral temperature of fasted SBT was also directly related to MR. In this case, source of heat is thought to be metabolic work performed within the red muscles which warmed the viscera through thermal conductance. Visceral excess temperatures were over 1°C warmer in larger than smaller SBT. Better heat retention ability of the larger SBT is likely attributed to improved retia mirabilia development and greater thermal inertia. SBT at 16°C maintained visceral excess temperatures significantly warmer than similarly sized fish at 19°C. This demonstrates some ability of SBT to physiologically regulate visceral warming. 6. In this study, the effect of progressively severe hypoxia levels on the swimming performance and metabolic scope of juvenile mulloway (Argyrosomus japonicus) were investigated. In normoxic conditions (6.85 mg l⁻¹), standard metabolic rate (SMR) and cost of transport were typical for subcarangiform fish species. Mulloway had a moderate scope for aerobic metabolism (5 times the SMR). The critical dissolved oxygen level was 1.80 mg l⁻¹ revealing that mulloway are well adapted to hypoxia. In all levels of hypoxia (5.23, 3.64, and 1.86 mg l⁻¹) the active metabolic rate was reduced however, the critical swimming velocity was reduced only at 3.64, and 1.86 mg l⁻¹. Mulloway metabolic scope was significantly reduced at all hypoxia levels, suggesting that even mild hypoxia may reduce growth productivity. / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2007

The thesis results of two laboratory experiments focusing on the impacts of predation risk, prey density and habitat complexity on predator-prey interaction strengths and predator metabolic rates, complemented by a brief review of the subject. The experimental system used in the first experiment consisted of cladoceran prey, larvae of three dragonfly species (Sympetrum sanguineum, Libellula quadrimaculata, Ischnura cf. elegans) as intermediate predators, and larvae of a large dragonfly species (Aeshna sp.) as a top predator. The second experiment of investigated how predation risk influences metabolic rates of the intermediate predators.