Skeletal muscle adaptation to exercise: a century of progress.
Skeletal muscle physiology and biochemistry is an established field with Nobel Prize-winning scientists, dating back to the 1920s. Not until the mid to late 1960s did there appear a major focus on physiological and biochemical training adaptations in skeletal muscle. The study of adaptations to exercise training reveals a wide range of integrative approaches, from the systemic to the molecular level. Advances in our understanding of training adaptations have come in waves caused by the introduction of new experimental approaches. Research has revealed that exercise can be effective at preventing and/or treating some of the most common chronic diseases of the latter half of the 20th century. Endurance-trained muscle is more effective at clearing plasma triglyceride, glucose, and free fatty acids. However, at the present time, most of the mechanisms underlying the adaptation of human skeletal muscle to exercise still remain to be discovered. Little is known about the regulatory factors (e.g., trans-acting proteins or signaling pathways) directly modulating the expression of exercise-responsive genes. Because so many potential physiological and biochemical signals change during exercise, it will be an important challenge in the next century to move beyond "correlational studies" and to identify responsible mechanisms. Skeletal muscle metabolic adaptations may prove to be a critical component to preventing diseases such as coronary heart disease, type 2 diabetes, and obesity. Therefore, training studies have had an impact on setting the stage for a potential "preventive medicine reformation" in a society needing a return to a naturally active lifestyle of our ancestors. (+info)
The Na(+)-K(+)-ATPase alpha2 gene and trainability of cardiorespiratory endurance: the HERITAGE family study.
The Na(+)-K(+)-ATPase plays an important role in the maintenance of electrolyte balance in the working muscle and thus may contribute to endurance performance. This study aimed to investigate the associations between genetic variants at the Na(+)-K(+)-ATPase alpha2 locus and the response (Delta) of maximal oxygen consumption (VO(2 max)) and maximal power output (W(max)) to 20 wk of endurance training in 472 sedentary Caucasian subjects from 99 families. VO(2 max) and W(max) were measured during two maximal cycle ergometer exercise tests before and again after the training program, and restriction fragment length polymorphisms at the Na(+)-K(+)-ATPase alpha2 (exons 1 and 21-22 with Bgl II) gene were typed. Sibling-pair linkage analysis revealed marginal evidence for linkage between the alpha2 haplotype and DeltaVO(2 max) (P = 0.054) and stronger linkages between the alpha2 exon 21-22 marker (P = 0.005) and alpha2 haplotype (P = 0.003) and DeltaW(max). In the whole cohort, DeltaVO(2 max) in the 3.3-kb homozygotes of the exon 1 marker (n = 5) was 41% lower than in the 8.0/3.3-kb heterozygotes (n = 87) and 48% lower than in the 8.0-kb homozygotes (n = 380; P = 0.018, adjusted for age, gender, baseline VO(2 max), and body weight). Among offspring, 10.5/10.5-kb homozygotes (n = 14) of the exon 21-22 marker showed a 571 +/- 56 (SE) ml O(2)/min increase in VO(2 max), whereas the increases in the 10.5/4.3-kb (n = 93) and 4.3/4.3-kb (n = 187) genotypes were 442 +/- 22 and 410 +/- 15 ml O(2)/min, respectively (P = 0.017). These data suggest that genetic variation at the Na(+)-K(+)-ATPase alpha2 locus influences the trainability of VO(2 max) in sedentary Caucasian subjects. (+info)
An inquiry-based teaching tool for understanding arterial blood pressure regulation and cardiovascular function.
Educators are placing a greater emphasis on the development of cooperative laboratory experiences that supplement the traditional lecture format. The new laboratory materials should encourage active learning, problem-solving, and inquiry-based approaches. To address these goals, we developed a laboratory exercise designed to introduce students to the hemodynamic variables (heart rate, stroke volume, total peripheral resistance, and compliance) that alter arterial pressure. For this experience, students are presented with "unknown" chart recordings illustrating pulsatile arterial pressure before and in response to several interventions. Students must analyze and interpret these unknown recordings and match each recording with the appropriate intervention. These active learning procedures help students understand and apply basic science concepts in a challenging and interactive format. Furthermore, laboratory experiences may enhance the students' level of understanding and ability to synthesize and apply information. In conducting this exercise, students are introduced to the joys and excitement of inquiry-based learning through experimentation. (+info)
Integration and regulation of cardiovascular function.
New methods in molecular biology and genetics have made possible many of the dramatic advances in physiological research that have occurred in recent years. For those of us who spend most of our time in the research laboratory, it si sometimes difficult to avoid a research-oriented, reductionist mind-set when discussing physiology with students. This article illustrates, with a few examples, the importance of conveying a "big picture" conceptual framework before discussing the details of cardiovascular physiology. Also, I have chosen examples from cardiac output and blood pressure regulation that show the importance of discussing cardiovascular physiology in terms of feedback control systems and integrating information from other areas, such as renal and endocrine physiology. Finally, I have highlighted the importance of two principles that I believe are often underemphasized in teaching physiology: mass balance and time dependence of physiological control systems. (+info)
Cardiovascular response to exercise.
This article is intended for instructors who teach cardiovascular physiology. In our physiology course exercise physiology is used as a tool to review and integrate cardiovascular and respiratory physiology. It is assumed that the students already have mastered the fundamentals of cardiovascular and respiratory physiology. Because this paper is part of a cardiovascular refresher course, I have deleted much of the respiratory physiology. The objectives of this presentation are for the student to 1) understand the relationship between maximal oxygen consumption and endurance during sustained exercise and be able to define "maximal oxygen consumption"; 2) understand the determinants of of maximal oxygen consumption; 3) understand the effects of dynamic exercise on the cardiovascular system and mechanisms for these effects; 4) understand the relationships between exercise intensity and major cardiorespiratory parameters, including heart rate, cardiac output, blood flow distribution, left ventricular stroke volume, arterial pressures, total peripheral resistance, and arterial and venous blood oxygen content; 5) be able to compare and contrast the cardiovascular effects of dynamic and isometric exercise in man and the mechanisms responsible for the major differences; and 6) be able to apply knowledge of the cardiovascular effects of exercise to understanding the causes of cardiovascular symptoms in disease and in diagnosis of disease states. This material contains many areas that stimulate discussion with students and allow exploration of concepts that are challenging for the student. This give and take between teachers and student is difficult to summarize in an article of this sort. Therefore, subjects that in my experience often stimulate questions and discussion with the students are indicated in the text. (+info)
Common misconceptions that arise in the first-year medical physiology curriculum concerning heart failure.
There are a number of misconceptions that first-year medical students have concerning the pathophysiology of heart failure. These stem from 1) a poor definition of heart failure, 2) a lack of care in distinguishing between similar but distinct concepts, and 3) the inability to recognize the relationship between the various stages of heart failure and the clinical manifestation of the disease. In this paper we provide a list of some of the misconceptions that we have encountered, some explanations of the distinctions to be made, and some of the rationale behind current surgical procedures and drug treatment. The misconceptions include failing to differentiate between the Frank-Starling mechanism and cardiac dilation as well as not grasping the significance that changes in cardiac beta-receptor function have in limiting the positive inotropic actions of circulating catecholamines. Finally, we review some of the altered neurohumoral mechanisms in heart failure and explain the basis for some common therapeutic approaches, including the use of angiotensin-converting enzyme inhibitors, in this disease. (+info)
Construction of a model demonstrating cardiovascular principles.
We developed a laboratory exercise that involves the construction and subsequent manipulation of a model of the cardiovascular system. The laboratory was designed to engage students in interactive, inquiry-based learning and to stimulate interest for future science study. The model presents a concrete means by which cardiovascular mechanics can be understood as well as a focal point for student interaction and discussion of cardiovascular principles. The laboratory contains directions for the construction of an inexpensive, easy-to-build model as well as an experimental protocol. From this experience students may gain an appreciation fo science that cannot be obtained by reading a book or interacting with a computer. Students not only learn the significant physiological concepts but also appreciate the importance of laboratory experimentation for understanding complex concepts. Model construction provides a hands-on experience that may substantially improve performance in science processes. We believe that model construction is an appropriate method for teaching advanced concepts. (+info)
A model circulatory system for use in undergraduate physiology laboratories.
The cardiovascular system is a central topic in physiology classes, yet it is difficult to provide undergraduates with quality laboratory experiences in this area. Thus a model circulatory system was developed to give students hands-on experience with cardiovascular fluid dynamics. This model system can be constructed from readily available materials at a reasonable cost. It has a realistic pressure drop across the different vessels. Using this system, students can investigate the effect that blood volume, vessel compliance, vessel construction, and heart activity have on blood pressure and flow. The system also demonstrates the effect of vessel diameter on resistance and fluid velocity. This model may give students a more concrete, intuitive feel for cardiovascular physiology. Another advantage is that it allows dramatic and easily controlled manipulations with quantitative results. Finally, its simple construction allows students to interchange components, giving them greater flexibility in experimentation. (+info)