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PubMed2004

Single- vs. multiple-set resistance training: recent developments in the controversy.

The number of sets in a resistance training program remains a major point of discussion and controversy. Studies prior to 1998 demonstrated inconsistent findings between single-set and multiple-set programs; however, recent evidence suggests that multiple sets promote additional benefits following short- and long-term training. The rationale supporting multiple sets is that the number of sets is part of the exercise volume equation, and the volume of exercise is crucial in producing the stimulus necessary to elicit specific physiological adaptations. The purpose of this paper is to present an overview of recent resistance training studies comparing single and multiple sets. However, it should be noted that studies to date have been conducted in young and middle-aged adults, and it remains to be determined if the additional benefits accrued with multiple-set training also occurs for older adults, especially the frail elderly.

Adaptation, Physiological↗

PubMed2006

Octopamine mediates thermal preconditioning of the locust ventilatory central pattern generator via a cAMP/protein kinase A signaling pathway.

We investigated the role of biogenic amines in generating thermoprotection of the ventilatory motor pattern circuitry in Locusta migratoria. Levels of octopamine (OA) and dopamine (DA) in the metathoracic ganglion decreased during heat stress. We measured the thermosensitivity of central pattern generation in response to a ramped increase of temperature in semi-intact preparations. OA, DA, and tyramine (TA) were either bath applied or injected into the locust hemocoel 4-8 h before testing. Neither TA nor DA modified the thermotolerance of ventilatory motor pattern generation. However, OA treatment by bath applications (10(-4) M OA) or by injections into the hemocoel (2 microg/10 microl OA) mimicked heat shock preconditioning and improved the thermotolerance of the motor pattern by increasing the failure temperature and by decreasing the time taken to recover operation after a return to room temperature. Heat shock-induced thermoprotection was eradicated in locusts preinjected with epinastine (Oct betaR antagonist). Neuropil injections of the cAMP agonist and protein kinase A (PKA) activator, Sp-cAMPs, both conferred thermoprotection in control locusts and rescued thermoprotection in epinastine-treated HS locusts. Similar injections of the PKA inhibitor Rp-cAMPs blocked the thermoprotective effect of bath-applied OA. Octopamine-mediated thermoprotection was also abolished with neuropil injections of cycloheximide or actinomycin D, indicating a requirement for transcription and translation. We conclude that OA has a crucial role in triggering protein synthesis-dependent physiological adaptations to protect CNS function during heat stress by activating a cAMP/PKA pathway.

Action Potentials↗

PubMed1987

[Ecological observations on Biomphalaria straminea (Dunker, 1848) in areas of the northeast, Brazil].

The different climatic regions determine the zoogeographic distribution of various animal species depending on their particular conditions and ecological preferences. The host schistosomiasis planorbid is one of these species. This paper deals with the distribution of Biomphalaria straminea in northeast Brazil. It starts from the analysis of different climatic peculiarities in this region, associated to limnological observation done by the author in three different hydric collections in the state of Sergipe. It has been concluded that this is an "eurióioca" species. Its broad ecological valence permits this species to survive in regions where climate asperties are evident, requiring behavior and physiological adaptations. The species survives in all northeast region, from "zona da mata", in the coast, to the semi-arid "sertão".

Adaptation, Physiological↗

PubMed2005

Resistance exercise training in patients with heart failure.

The utility, safety and physiological adaptations of resistance exercise training in patients with chronic heart failure (CHF) are reviewed and recommendations based on current research are presented. Patients with CHF have a poor clinical status and impaired exercise capacity due to both cardiac limitations and peripheral maladaptations of the skeletal musculature. Because muscle atrophy has been demonstrated to be a hallmark of CHF, the main principle of exercise programmes in such patients is to train the peripheral muscles effectively without producing great cardiovascular stress. For this reason, new modes of training as well as new training methods have been applied. Dynamic resistance training, based on the principles of interval training, has recently been established as a safe and effective mode of exercise in patients with CHF. Patients perform dynamic strength exercises slowly, on specific machines at an intensity usually in the range of 50-60% of one repetition maximum; work phases are of short duration (< or =60 seconds) and should be followed by an adequate recovery period (work/recovery ratio >1 : 2). Patients with a low cardiac reserve can use small free weights (0.5, 1 or 3 kg), elastic bands with 8-10 repetitions, or they can perform resistance exercises in a segmental fashion. Based on recent scientific evidence, the application of specific resistance exercise programmes is safe and induces significant histochemical, metabolic and functional adaptations in skeletal muscles, contributing to the treatment of muscle weakness and specific myopathy occurring in the majority of CHF patients. Increased exercise tolerance and peak oxygen consumption (V-dotO(2peak)), changes in muscle composition, increases in muscle mass, alterations in skeletal muscle metabolism, improvement in muscular strength and endurance have also been reported in the literature after resistance exercise alone or in combination with aerobic exercise. According to new scientific evidence, appropriate dynamic resistance exercise should be recommended as a safe and effective alternative training mode (supplementary to conventional aerobic exercise) in order to counteract peripheral maladaptation and improve muscle strength, which is necessary for recreational and daily living activities, and thus quality of life, of patients with stable, CHF.

Adaptation, Physiological↗

PubMed2006

Visual physiology of the Antarctic amphipod Abyssorchomene plebs.

Although the visual systems of animals living in the cold, dark water of the deep sea have been investigated for some time, little is known about vision in animals inhabiting polar oceans, where temperatures are even colder and irradiance fluctuates dramatically with ice cover and season. Physiology of the compound eye of the amphipod Abyssorchomene plebs (Gammaridea: Lysianassoidea), a common Antarctic benthic scavenger, was studied electrophysiologically by electroretinography. A. plebs has a monochromatic visual system with a spectral sensitivity maximum at 487 nm, and higher sensitivity at ultraviolet wavelengths than predicted by a visual pigment template. While irradiance sensitivity determined from V/log I curves is comparable to that of mesopelagic crustaceans, temporal resolution calculated from response waveform dynamics and as determined by critical flicker fusion frequency suggest that the A. plebs eye is slower than that of crustaceans from the deep sea. A. plebs photoreceptors are physiologically adapted for a slow lifestyle in a low-light environment, where maximizing photon capture occurs at the expense of detecting fast events in the visual scene.

Adaptation, Physiological↗

PubMed1983

Ruminant cold stress: effect on production.

A review is presented of biological issues and practical consequences of the effects of cold stress on ruminant animals. When animals are subjected to extreme cold stress, substantial dietary energy may be diverted from productive functions to the generation of body heat. Failure to produce sufficient heat can result in death. More often, however, cold stress leads to the development of secondary changes and possibly disease. With prolonged exposure to even mildly cold conditions, physiological adaptation occurs in animals resulting in increases in thermal insulation, appetite and basal metabolic intensity, as well as alterations in digestive functions. Much of the reduced productivity, and in particular the reduced nutritional efficiency, observed in ruminant production systems during the colder part of the year, can be accounted for by these adaptive changes.

Adaptation, Physiological↗

PubMed2001

Reproductive loss in high-producing dairy cattle: where will it end?

The dairy industry in the United States has changed dramatically in the last decade. Milk production per cow has increased steadily because of a combination of improved management, better nutrition, and intense genetic selection. Dairy farms are larger, and nearly 30% of the dairy cows in the United States are on farms with 500 or more cows. The shift toward more productive cows and larger herds is associated with a decrease in reproductive efficiency. Cows with the greatest milk production have the highest incidence of infertility, but epidemiological studies suggest that, in addition to milk production, other factors are probably decreasing reproductive efficiency in our dairy herds. The reproductive physiology of dairy cows has changed over the past 50 yr, and physiological adaptations to high milk production may explain part of the reproductive decline. Critical areas for new research include control of the estrous cycle, metabolic effects of lactation on reproduction, mechanisms linking disease to reproduction, and early embryonic mortality. Solving reproductive loss in dairy cows will not be easy because only a small number of research groups study reproduction in postpartum dairy cows. Therefore, the present research base will need to be expanded. For this to occur, research funding must be increased above its current level and a renewed emphasis must be placed on solving the emerging crisis of infertility in dairy cows.

Adaptation, Physiological↗

PubMed2000

Sudden cardiac death in young athletes. Causes, athlete's heart, and screening guidelines.

Sudden cardiac death of a young competitive athlete is a rare but tragic event. Hypertrophic cardiomyopathy and coronary artery anomalies are the most frequent causes. Most cardiovascular abnormalities go unrecognized until the time of death owing to the lack of preceding signs or symptoms suggestive of disease. Physicians responsible for the care of athletes should be familiar with the various causes of sudden cardiac death, the physiologic adaptations seen in so-called athlete's heart, and existing cardiovascular screening guidelines. The preparticipation evaluation, although it has limitations, is the major instrument readily available for prevention of sudden cardiac death. Effort should be made to follow established consensus guidelines.

Adaptation, Physiological↗

PubMed1992

Prudent strategies for elective red blood cell transfusion.

OBJECTIVE: To review the literature on the appropriateness of red blood cell transfusion and current physician practice, with emphasis on the physiologic and symptomatic implications of elective transfusion in the treatment of anemia. DATA SOURCES: Studies on the therapeutic use of red blood cell transfusion were identified through a search of MEDLINE (1966 to the present) and through a manual review of bibliographies of identified articles. In addition, evidence was solicited from selected experts in the field and recent consensus panels that have developed transfusion guidelines. DATA SYNTHESIS: No controlled trials of blood transfusion were identified, but data were available on four issues relevant to transfusion practice: current physician practice and evidence for excessive use of red blood cell transfusion; physiologic adaptation to anemia; human tolerance of low hemoglobin levels; and strategies for reducing homologous transfusion requirements. CONCLUSIONS: Despite the recent decline in red blood cell use because of concerns about infection, current transfusion practice remains variable because physicians have disparate views about its appropriateness. The remarkable human tolerance of anemia suggests that clinicians can accept hemoglobin levels above 70 g/L (7 g/dL) in most patients with self-limited anemia. In patients with impaired cardiovascular status or with anemias that will not resolve spontaneously, however, the data are insufficient to determine minimum acceptable hemoglobin levels, and therapy must be guided by the clinical situation. Several therapeutic strategies and pharmacologic interventions are available in the perioperative and non-operative settings to further reduce red blood cell use.

Adaptation, Physiological↗

PubMed1999

Effects of thermal acclimation on the relaxation system of crucian carp white myotomal muscle.

Many cyprinid fish are able to compensate for a decrease in ambient temperature by process of physiological adaptation in the function of muscles. In the winter habitat of crucian carp (Carassius carassius L.), low temperature is associated with simultaneous oxygen shortage. Because of the oxygen deprivation, there is probably little space for compensatory adaptation because positive thermal compensation would increase energy demand and accelerate depletion of glycogen reserves. Thus, we assumed that the crucian carp, unlike many other cyprinid fish, would not show positive thermal compensation but either no compensation or inverse compensation in muscle function. To test this hypothesis in the relaxation system of skeletal muscles, we determined the parvalbumin content and the activity of sarcoplasmic reticular (SR) Ca-ATPase in white myotomal muscle of winter- and summer-acclimated crucian carp. In the laboratory, the winter fish were kept at 2 degrees C and the summer fish at 22 degrees C for a minimum of 3 weeks before the experiments. The specific activity of SR Ca-ATPase at low experimental temperature (2 degrees C) was similar in summer- and winter-acclimated fish (0.26 +/- 0.04 vs. 0.25 +/- 0.04 mM/mg/min; P > 0.05). Because of the bigger Q(10) of cold-acclimated carp, the enzyme activity at 30 degrees C was higher in cold-acclimated winter fish than in warm-acclimated summer fish (7.42 +/- 0.90 vs. 5.18 +/- 0.53 mM/mg/min; P < 0.05). In contrast, the yield of SR protein was 70% higher in summer than winter fish (0.315 +/- 0.045 vs. 0.187 +/- 0.017 mg/g; P < 0.001). Because of these opposing changes, total Ca-ATPase activity of SR (per gram muscle weight) remained relatively constant. Similarly, the parvalbumin content of the myotomal muscle was not different between summer (4.09 +/- 0.95 mg/g) and winter (3.70 +/- 0.60 mg/g) fish. Although there were no seasonal changes in the total relaxing system of the crucian carp white myotomal muscle, the same activity of SR Ca-ATPase in winter fish was obtained with less amount of SR pump protein, owing to the increased catalytic activity of the enzyme. The higher catalytic activity of winter fish SR Ca-ATPase might be caused by differences in fatty acid composition noted in membrane lipids; i.e., fewer saturated fatty acids and more n-6 polyunsaturated fatty acids (PUFAs), at the expense of n-3 PUFAs, were present in the SR of cold-acclimated winter fish. Temperature-induced changes in enzyme protein, however, cannot be excluded. Thus, the present results indicate the absence of positive thermal compensation in the relaxing system of crucian carp white muscle. It seems, however, that lipid composition of SR membranes and temperature dependence of SR Ca-ATPase are altered by seasonal acclimation.

Adaptation, Physiological↗

PubMed1993

A review of muscle atrophy in microgravity and during prolonged bed rest.

With the prospect of long duration space missions in Earth orbit or to Mars, there is a need for adequate information on the physiological adaptations that will occur. One consequence of prolonged exposure to microgravity is muscle atrophy (loss of muscle mass). After a long duration space flight, muscle atrophy along with skeletal calcium loss would affect the capacity of astronauts to re-adapt to gravity on return to Earth. Of importance are any countermeasures which can attenuate the adaptive responses to microgravity. Experimentation is difficult in space with small subject numbers and mission constraints. Prolonged bed rest using healthy volunteers is used as an Earth-based model to simulate the muscle atrophy which occurs in the microgravity environment.

Adaptation, Physiological↗

PubMed2002

Exercise in pregnancy.

This article is a brief overview of a vast area of interest, in which we are learning that women can be encouraged to help their bodies cope with the physiological adaptations of pregnancy, and to enjoy what is usually a very special time in their lives. Although the studies carried out have only been very small, moderate exercise has not shown any harmful effects in healthy pregnant women, and these findings encourage us, as healthcare professionals, to support women in their choice to exercise during pregnancy, with known beneficial outcomes for both mother and baby.

Adaptation, Physiological↗

PubMed1973

Effects of chronic acceleration in animals.

Chronic acceleration describes the exposure of animals to increased acceleration fields of sufficient intensity and duration to induce physiological adaptation. By comparing the degree of changes observed in several fields with the acceleration intensity, it is possible to derive an estimate of the biological effect of gravity. For technical reasons, such studies are limited to artificial fields produced by protracted centrifugation. Observations by various investigators indicate a fairly general response to chronic acceleration. Over the size range presented by these species (0.04-5 kg), there appears to be a direct relationship between body mass and the degree of the acceleration-induced effect (tolerable field intensity, growth repression, inhibition of fat (correction of far) deposition, etc.). However, different response patterns may obtain in homeotherms that differ significantly from this body size range.

Acceleration↗

PubMed2006

[Physical exercise, oxidative stress and damage].

Physical activities (aerobic, anaerobic and resistance exercises) evoke an increased production of high oxidative substances, depending mainly on the intensity of the muscle actions. Antioxidants in the muscle and blood represent the first line of defense, but an oxidative stress activates the scavenger enzyme systems. If the stress is too high, structural modifications, "damage" of lipids, proteins and nucleic acids is a consequence. Markers of this oxidative damage can be recognized for a few days. Oxidative stress certainly have a role in the physiological adaptation to the physical activity. Moderate intensity (less than 50-60% of the aerobic capacity or of the maximal muscle tension) exercises exert low stress without oxidative damage impulse in the normally nourished subjects. Regular training and "normal" diet results a proper defense against excess oxidative stress. Monitoring of the oxidative stress or/and damage is not jet a tool in the training praxis in spite of the obvious advantages and of the existence of certain noninvasive methods. Data reinforce the necessity of regular exercise with moderate intensity in the primary prevention and in the rehabilitation of metabolic and cardiovascular diseases.

Adaptation, Physiological↗

PubMed1986

Some emerging general principles in the pathogenesis of hepatocellular carcinoma.

A rational concept of the key steps in the multistep process of cancer development in liver is emerging. This concept proposes that the strategy of cancer development consists of two major sequences: (a) the genesis of persistent benign focal proliferations (clonal nodules) and (b) the development of hepatocellular cancer from one or more such nodules. Sequence (a) comprises the classical 'initiation and promotion' of chemical carcinogenesis. Sequence (b) is dominated by persistent cell proliferation. In the precancerous steps, cell proliferation is almost balanced by cell loss, leading to only a slow increase in the size of the nodules. With cancer, this balance is lost, leading to a much more rapid enlargement of the focal lesion. The carcinogenic process in the liver is viewed initially as a form of physiological adaptation to certain types of xenobiotic agents generating new focal cell populations. The animals with such new focal lesions are much better able to resist the toxic or lethal effects of many environmental hazards. According to this view, liver cancer development is a consequence of a derivative of the basic adaptation process.

Adaptation, Physiological↗

PubMed1987

[Health and fertility in relation to production. Climate and health in young farm animals].

In animals, the climatic factor of environmental temperature causes specific physiological adaptations dependant on the nature and duration of the 'stressor'. The absolute temperature appears to be of less importance in influencing animal health than the extent of deviation from the thermoneutral zone. The difficulty experienced by animals in maintaining thermoregulation affects the immunological response and possibly also resistance. In the literature, the duration and type of changes involved are not always clearly stated. This may explain why the reactions to cold and warmth are not always identical. Also, the reactions which partly influence resistance are sometimes not compatible with climatic stress. Further research is needed for improved understanding of the relationship between the resistance of the animal and the duration and extent of climatic stress.

Adaptation, Physiological↗

PubMed1985

Rehabilitating the severely malnourished infant and child.

The failure of public health measures to control protein-energy malnutrition means that continued therapeutic, curative programs for the rehabilitation of severely malnourished infants and children will be needed for the foreseeable future. Successful rehabilitation requires an understanding of the biology of malnutrition and of the dietary guidelines for provision of appropriate formulas. It is important to recognize that protein-energy malnutrition represents a metabolically and physiologically adapted state but that full recuperation entails compensatory weight gain for recovery of the expected weight for height and body composition. Overzealous early feeding is to be avoided; protein- and energy-rich diets must be introduced gradually and sustained to provide the nutrients necessary for rapid catch-up growth. Therapy involves a three-stage process of addressing acute problems, restoring nutrient balance, and ensuring nutritional rehabilitation. Despite intestinal changes due to malnutrition, intact milk provides a suitable protein source for formulation of recovery diets. As long as protein-energy malnutrition remains prevalent, research to improve its treatment will remain a high investigative priority.

Adaptation, Physiological↗

PubMed1979

Effects of surrogate mothering on physiologic stabilization in transitional newborns.

This experimental study was conducted to determine whether surrogate mothering during the first hours of life will affect physiologic stabilization in the transitional newborn. Two groups of 8 normal newborns were studied. The treatment was given on cue and consisted of rocking, cuddling, visual and verbal interaction, and non-nutritive sucking to satiety. The control group received routine nursing care. The experimental group's mean axillary temperature correlated with increasing age (r = +.91, p less than .001) and leveled at 2 hours of life at 98.2 degrees F (36.8 degrees C). Control group temperatures fell continuously to 97.4 degrees F (36.3 degrees C) following removal of the newborn from under an infrared heat unit. The experimental group's mean respiratory rate correlated negatively with increasing age (r = -.81, p less than .009). The experimental group's mean heart rate was higher at 3 1/2 hours (p less than .01). The control group's mean heart rate correlated over time (= -.82, p less than .007). Heart murmurs were heard 16 times in 5 controls and 6 times in 3 treated newborns. The frequency difference was significant (p less than .05). Experimental newborns cried an average of 2.1 minutes. This was less (p less than .01) than the controls (38.5 minutes). Electronically measured sucking strength was higher (p less than .001) for the treated newborns (81.5 mm Hg) than for the controls (20.5 mm Hg) prior to the first feeding at 4 hours. The experimental group ingested a mean of 13.75 cc of sterile water at the initial feeding, compared to 5 cc for the controls. Sucking and swallowing difficulty was seen in 6 control and 3 experimental newborns. These data suggest that interaction and soothing by another human facilitates transitional newborn physiologic adaptation.

Adaptation, Physiological↗