Insulin and contraction-mediated glucose transporter 4 (GLUT4) trafficking have different kinetics in mature skeletal muscle. Intravital imaging indicates that insulin-stimulated GLUT4 trafficking differs between t-tubules and sarcolemma. In contrast, contraction-induced GLUT4 trafficking does not differ between membrane surfaces. This distinction is likely due to differences in the underlying signaling pathways regulating GLUT4 vesicle depletion, GLUT4 membrane fusion and GLUT4 re-internalization.
Living mice; Intravital; In-Vivo; PI3-Kinase; AMP-Kinase; LKB1
Routine activities performed while standing and walking require the ability to appropriately and continuously modulate postural movements as a function of a concurrent task. Changes in task-dependent postural control contribute to the emergence, maturation, and decline of complex motor skills and stability throughout the lifespan.
Postural Control; Stability; Lifespan Development; Multi-task behavior; Mobility; Load Handling; Adaptive Locomotion
Protein synthesis rates are commonly measured by using isotopic tracers to quantify the incorporation of a labelled amino acid into muscle proteins. Here we provide evidence supporting our hypothesis that the non-isotopic SUnSET technique is a valid and accurate method for the measurement of in vivo changes in protein synthesis at the whole muscle and single muscle fiber levels.
skeletal muscle; translation; hypertrophy; atrophy; puromycin; muscle fiber type; myosin heavy chain
There is increasing evidence that physical activity (PA) can enhance weight loss and other outcomes after bariatric surgery. However, most preoperative patients are insufficiently active, and without support, fail to make substantial increases in their PA postoperatively. This review provides the rationale for PA counseling in bariatric surgery and describes how to appropriately tailor strategies to pre- and postoperative patients.
exercise; severe obesity; treatment; clinical care; gastric bypass; laparoscopic adjustable gastric band
Ventilatory limitation to exercise remains an important unresolved clinical issue; as a result, many individuals misinterpret the effects of expiratory flow limitation as an all-or-nothing phenomenon. Expiratory flow limitation is not all-or-none; approaching maximal expiratory flow can have important effects not only on ventilatory capacity but also on breathing mechanics, ventilatory control, and possibly exertional dyspnea and exercise intolerance.
dynamic compression of the airways; maximal expiratory flow; breathing mechanics; ventilatory limitations to exercise; ventilatory limitations; ventilatory constraints; cardiopulmonary exercise testing
African Americans have endothelial dysfunction which likely contributes to their high prevalence of hypertension. Endothelial cell responses to stimuli could play a role in the development of endothelial dysfunction and hypertension. High physiological levels of vascular laminar shear stress can profoundly alter endothelial cell phenotype. It is not known whether there are race-dependent endothelial cell responses to laminar shear stress.
Endothelial cell; shear stress; exercise; African American; oxidative stress; inflammation
Regulation of skeletal muscle capillarization involves distinct signaling pathways and growth factors including nitric oxide and vascular endothelial growth factor. Our understanding of this complex regulation continues to expand with the identification of new angiogenic growth factors. Future work needs to increase the use of advanced molecular techniques to expand our knowledge of the regulation of basal and exercise-induced capillarization.
capillaries; exercise; mitochondria; muscle fiber size; VEGF; nitric oxide; 5′-AMP activated protein kinase
This review presents the hypothesis that muscle is a source of secreted factors (myokines) that can influence bone mass in both positive and negative ways. Growth factor secretion by muscle may therefore be one pathway through which mechanical signals are transduced biologically.
IGF-1; FGF-2; Myostatin; periosteum; muscle injury
Severe obesity is increasing at a disproportionate rate compared to milder grade obesity. Our research group has obtained evidence indicative of an “obesity metabolic program” in the skeletal muscle of severely obese individuals which may be genetically or epigenetically determined. We believe this represents a paradigm shift in thinking about metabolic regulation in obesity.
Bariatric surgery; Exercise training; Fat oxidation; Class III obesity; Insulin action; Mitochondria; Obesity
Statins are effective for reducing low-density lipoprotein cholesterol and cardiac events, but can produce muscle side effects. We have hypothesized that statin-related muscle complaints are exacerbated by exercise and influenced by factors including mitochondrial dysfunction, membrane disruption and/or calcium handling. The interaction between statins, exercise and muscle symptoms may be more effectively diagnosed and treated as rigorous scientific studies accumulate.
cholesterol-lowering medication; muscle strength; aerobic capacity; myalgia; Vitamin D; HMG CoA Reductase Inhibitor
Human exposure to cold stimulates cutaneous vasoconstriction by activating both sympathetic reflex and locally mediated pathways. Older humans are vulnerable to hypothermia because primary aging impairs thermoregulatory cutaneous vasoconstriction. This article highlights recent findings discussing how age-related decrements in sympathetic neurotransmission contribute directly to thermoregulatory impairment, whereas changes in local cold-induced intracellular signaling suggest a more generalized age-associated vascular dysfunction.
skin blood flow; aging; temperature regulation; adrenergic; Rho kinase; cold
Enhanced external counterpulsation (EECP) is a non-invasive treatment for coronary artery disease (CAD) patients who have angina pectoris that is refractory to pharmacotherapy and revascularization. The popular concept is that EECP may promote collateral development and improve myocardial perfusion. We hypothesize that improvements in peripheral arterial function are responsible for the clinical benefits of EECP.
angina pectoris; nitric oxide; endothelium; flow-mediated dilation; arterial stiffness
Mitochondria are dynamic organelles in skeletal muscle critical in physical performance and disease. The mitochondrial life cycle spans biogenesis, maintenance, and clearance. Exercise training may promote each of these processes, conferring positive impacts on skeletal muscle contractile and metabolic functions. This review focuses on the regulation of these processes by endurance exercise and discusses potential benefits in health and disease.
Skeletal muscle; exercise-induced adaptation; mitochondrial biogenesis; mitochondrial fission; mitochondrial fusion; autophagy; mitophagy
Questionnaires that assess active and sedentary behaviors in large-scale epidemiologic studies are known to contain substantial errors. We present three options for improving measures of physical activity behaviors in large-scale epidemiologic studies, discuss the problems and prospects for each of these options, and highlight a new direction for measuring these behaviors in such studies.
Exposure assessment; Exercise; Sitting; Measurement error; Disease prevention
Concussion has been viewed historically as a transient injury with no evidence supporting the existence of persistent effects. However, our recent work demonstrates electroencephalographic and motor control changes in otherwise healthy individuals with a history of concussion. We therefore hypothesize that concussive and subconcussive head impacts set about a cascade of pathological events that accelerates declines in cognitive function typically associated with the aging process.
Endogenous heat shock proteins (HSP) are decreased in disease states associated with insulin resistance and aging. Induction of HSPs has been shown to decrease oxidative stress, inhibit inflammatory pathways, and enhance metabolic characteristics in skeletal muscle. As such, HSPs have the potential to function as an important defense system against the development of insulin resistance and type 2 diabetes.
insulin signaling; glucose uptake; oxidative stress; stress kinases; mitochondria; aging; obesity
Older adults exhibit greater motor variability, which impairs their accuracy and function, compared with young adults. Low-intensity training that emphasizes muscle coordination reduces variability in older adults. Furthermore, low amount of visual feedback minimizes age-associated differences in variability. We hypothesize that an intervention that combines muscle coordination and reduced visual feedback would be advantageous to improve motor control in older adults.
neuromuscular control; force variability; movement control; aging; intervention; training
Total knee arthroplasty (TKA) is associated with persistent quadriceps dysfunction. Since quadriceps dysfunction impairs functional performance, minimizing quadriceps dysfunction by attenuating central activation deficits early after surgery may improve function later in life. Rehabilitation strategies incorporating neuromuscular electrical stimulation and early, aggressive quadriceps strengthening may prove beneficial. Further, surgical approaches such as minimally invasive TKA may minimize post-operative quadriceps dysfunction.
Strength; muscle inhibition; rehabilitation; neuromuscular electrical stimulation; joint replacement
Muscle power declines earlier and more precipitously with advancing age compared to muscle strength. Peak muscle power has also emerged as an important predictor of functional limitations in older adults. Our current working hypothesis is focused on examining lower extremity muscle power as a more discriminant variable for understanding the relationships between impairments, functional limitations and resultant disability with aging.
Aging; muscle power; exercise physiology; physical function; mobility-disability
Physical activities undertaken in childhood, particularly activities which apply large forces quickly convey optimal benefits to bone mass, size, and structure. Evidence is accumulating that benefits persist well beyond activity cessation. This review examines the potential for early childhood activity to improve bone mineralization and structure and explores childhood activity as prevention for osteoporosis in later life.
Osteoporosis; Bone mineral content; Bone strength; Weight-bearing physical activity; Puberty; Peak bone mass
This commentary focuses on the issues of statistical power, the usefulness of hypothesis-free approaches such as in genome-wide association explorations, the necessity of expanding the research beyond common DNA variants, the advantage of combining transcriptomics with genomics, and the complexities inherent to the search for links between genotype and phenotype in exercise genomics research.
exercise genomics; candidate genes; single nucleotide polymorphism; genome-wide association study; genomic predictors
Even when adults meet physical activity guidelines, sitting for prolonged periods can compromise metabolic health. TV time and objective-measurement studies show deleterious associations, and breaking up sedentary time is beneficial. Sitting time, TV time, and time sitting in automobiles increase premature mortality risk. Further evidence from prospective studies, intervention trials, and population-based behavioral studies is required.
environmental and social change; TV time; breaks in sedentary time; accelerometer measurement; blood glucose; triglycerides; metabolic health
Mitochondrial dysfunction and oxidative stress are thought to play important roles in mammalian aging. Resveratrol is a plant-derived polyphenol that exerts diverse anti-aging activities, mimicking some of the molecular and functional effects of dietary restriction. This review focuses on the molecular mechanisms underlying the mitochondrial protective effects of resveratrol, which could be exploited for the prevention or amelioration of age-related diseases in the elderly.
senescence; bioenergetics; mitochondria; aging; caloric restriction; cardiovascular disease; phytochemicals; 3,5,4′-trihydroxystilbene