Advances in imaging methods have led to new capability to study muscle and tendon motion in vivo. Direct measurements of muscle and tendon kinematics using imaging may lead to improved understanding of musculoskeletal function. This review presents quantitative ultrasound methods for muscle dynamics that can be used to assess in vivo musculoskeletal function when integrated with other conventional biomechanical measurements.
muscle elastography; muscle kinematics; contraction velocity; strain rate; vector Doppler Imaging
Skeletal muscle function can be altered by changes in protein structure and motion. Electron paramagnetic resonance (EPR) paired with site-directed spin labeling has been used to study the relationships between (a) muscle force and myosin structure and (b) muscle relaxation and Ca-ATPase motion and structure.
skeletal muscle; aging; myosin; Ca-ATPase; protein structure; aggregation
Operant conditioning protocols can gradually change spinal reflexes, which are the simplest behaviors. This article summarizes the evidence supporting two propositions: that these protocols provide excellent models for defining the substrates of learning; and that they can induce and guide plasticity to help restore skills such as locomotion that have been impaired by spinal cord injury or other disorders.
Skill acquisition; H-reflex; spinal cord plasticity; learning; locomotion; spinal cord injury
In this review, we summarize current evidence for a direct effect of vitamin D on skeletal muscle. A number of studies identify the receptor for 1,25-dihydroxyvitamin-D3 (vitamin D receptor (VDR)) and the enzyme CYP27B1 (1-α-hydroxylase) in muscle. We hypothesize that vitamin D acts on myocytes via the VDR, and we examine proposed effects on myocyte proliferation, differentiation, growth, and inflammation.
skeletal muscle; vitamin D; vitamin D receptor; aging; 25-hydroxyvitamin D
Some health-related proteins such as lipoprotein lipase may be regulated by qualitatively different processes over the physical activity continuum, sometimes with very high sensitivity to inactivity. The most powerful process known to regulate lipoprotein lipase protein and activity in muscle capillaries may be initiated by inhibitory signals during physical inactivity, independent of changes in lipoprotein lipase messenger RNA.
dose response; coronary heart disease (CHD); transcription; posttranslational; signaling; sedentary; aging
Voluntary exercise reduces the incidence of stress-related psychiatric disorders in humans and prevents serotonin-dependent behavioral consequences of stress in rodents. Evidence reviewed herein is consistent with the hypothesis that exercise increases stress resistance by producing neuroplasticity at multiple sites of the central serotonergic system, which all help to limit the behavioral impact of acute increases in serotonin during stressor exposure.
wheel running; learned helplessness; anxiety; depression; prefrontal cortex; dorsal raphe nucleus
We have used site-directed spin labeling and electron paramagnetic resonance (EPR) to explore the effects of oxidation on muscle function, with particular focus on the actin-myosin interaction. EPR measurements show that aging or oxidative modification cause a decrease in the fraction of myosins in the strong-binding state, which can be traced to the actin-binding cleft of the myosin catalytic domain.
myosin; actin; muscle; Reactive Oxygen Species (ROS); methionine; aging
Most brain studies of Parkinson’s disease (PD) focus on patients who are already taking anti-parkinsonian medication. This makes it difficult to isolate the effects of disease from those of treatment. We review MRI evidence supporting the hypothesis that early-stage, untreated PD patients have structural and functional abnormalities in the brain, some of which are related to motor symptoms.
diffusion tensor imaging (DTI); functional magnetic resonance imaging (fMRI); parkinsonism; grip force; subtype; de novo; movement
We review practice-induced changes in two variance components defined based on the uncontrolled manifold hypothesis: One of them affects task performance while the other one does not. Practice leads to a drop in the former component (higher accuracy), while the latter can drop, stay unchanged, or even increase. The last scenario can be achieved with practice that challenges performance stability.
Synergy; practice; variability; redundancy; abundance
The loss of skeletal muscle size and function with aging, sarcopenia, may be related, in part, to an age-related muscle protein synthesis impairment. In this review, we discuss to what extent aging affects skeletal muscle protein synthesis and how nutrition and exercise can be strategically employed to overcome age-related protein synthesis impairments and slow the progression of sarcopenia.
Aging; Sarcopenia; Exercise; Protein; Insulin; Muscle Protein Synthesis; mTORC1
To decelerate the body and limbs, muscles actively lengthen to dissipate energy. During rapid energy-dissipating events, tendons buffer the work done on muscle by temporarily storing elastic energy, then releasing this energy to do work on the muscle. This elastic mechanism may reduce the risk of muscle damage by reducing peak forces and lengthening rates of active muscle.
Muscle; tendon; elastic energy; energy dissipation; deceleration
Acute Respiratory Failure patients experience significant muscle weakness which contributes to prolonged hospitalization and functional impairments post-hospital discharge. Based on our previous work, we hypothesize that an exercise intervention initiated early in the intensive care unit aimed at improving skeletal muscle strength could decrease hospital stay and attenuate the deconditioning and skeletal muscle weakness experienced by these patients.
Early exercise has the potential to decrease hospital length of stay and improve function in Acute Respiratory Failure patients.
Length of Stay; Physical Function; Mobility; Intensive Care Unit; Strength Training
Skeletal muscle comprises approximately 40 % of total body mass and, as such, contributes to maintenance of human health. In this review we will discuss the current state of knowledge regarding the role of molecular clocks in skeletal muscle. In addition we discuss a new function for exercise as a time setting cue for muscle and other peripheral tissues.
circadian; skeletal muscle; exercise; peripheral tissues; zeitgeber
Skeletal muscle contractile function declines with age and age-associated diseases. Although muscle atrophy undoubtedly contributes to this decrease, recent findings suggest that reduced myofilament protein content and function also may participate. Based on these data, we propose that age- and disease-related alterations in myofilament proteins represent one molecular mechanism contributing to the development of physical disability.
myosin; actin; muscle; human; fiber; molecular
Neuromuscular control of the trunk and knee predicts anterior cruciate ligament injury risk with high sensitivity and specificity. These predictors are linked, as lateral trunk positioning creates high knee abduction torque (load). The hypotheses explored are that lateral trunk motion increases load and that neuromuscular training that increases trunk control will decrease load.
knee injury; high risk biomechanics; ACL injury prevention; neuromuscular control; female sports injuries; identification of knee injury risk factors
SIRT1 is a purported central regulator of skeletal muscle mitochondrial biogenesis. Herein we discuss our recent work utilizing conditional mouse models, which highlight the complexities of SIRT1 biology in vivo, and question its role in regulating mitochondrial function and mitochondrial adaptions to endurance exercise. Further, we discuss the possible contribution of proposed SIRT1 substrates to muscle mitochondrial biogenesis.
Exercise; sirtuins; acetylation; transcription; adaptation
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