Mechanisms of the deep, slow-wave, sleep-related increase of upper airway muscle tone in healthy humans
Upper airway muscle activity is reportedly elevated during slow-wave sleep (SWS) when compared with lighter sleep stages. To uncover the possible mechanisms underlying this elevation, we explored the correlation between different indices of central and reflex inspiratory drive, such as the changes in airway pressure and end-expiratory CO2 and the changes in the genioglossus (GG) and tensor palatini (TP) muscle activity accompanying transitions from the lighter N2 to the deeper N3 stage of non-rapid eye movement (NREM) sleep in healthy young adult men. Forty-six GG and 38 TP continuous electromyographic recordings were obta...
Source: Journal of Applied Physiology - May 18, 2017 Category: Physiology Authors: Hicks, A., Cori, J. M., Jordan, A. S., Nicholas, C. L., Kubin, L., Semmler, J. G., Malhotra, A., McSharry, D. G. P., Trinder, J. A. Tags: RESEARCH ARTICLE Source Type: research
Exposure-response modeling of flow-mediated dilation provides an unbiased and informative measure of endothelial function
In this study, we developed an exposure-response, model-based approach that not only quantifies FMD based on the rich velocity and diameter data, it overcomes previously acknowledged challenges. FMD data were obtained from 15 apparently healthy participants, each exposed to four different cuff occlusion durations. The velocity response following cuff release was described by an exponential model with two parameters defining peak velocity and rate of decay. Shear exposure derived from velocity was used to drive the diameter response model, which consists of additive constriction and dilation terms. Three parameters describi...
Source: Journal of Applied Physiology - May 18, 2017 Category: Physiology Authors: Van Brackle, C. H., Harris, R. A., Hallow, K. M. Tags: RESEARCH ARTICLE Source Type: research
Occlusion of blood flow attenuates exercise-induced hypoalgesia in the occluded limb of healthy adults
Animal studies have demonstrated an important role of peripheral mechanisms as contributors to exercise-induced hypoalgesia (EIH). Whether these same mechanisms contribute to EIH in humans is not known. In the current study, pain thresholds were assessed in healthy volunteers (n = 36) before and after 5 min of high-intensity leg cycling exercise and an equivalent period of quiet rest. Pressure pain thresholds (PPTs) were assessed over the rectus femoris muscle of one leg and first dorsal interosseous muscles (FDIs) of both arms. Blood flow to one arm was occluded by a cuff throughout the 5-min period of exercise (or rest) ...
Source: Journal of Applied Physiology - May 18, 2017 Category: Physiology Authors: Jones, M. D., Taylor, J. L., Barry, B. K. Tags: RESEARCH ARTICLE Source Type: research
Sarcolipin expression is not required for the mitochondrial enzymatic response to physical activity or diet
In mice, transgenic manipulation of Ca2+-handling proteins is sufficient to alter the metabolic phenotype of muscle. We have previously shown that ablation of sarcolipin (SLN), a regulatory protein and uncoupler of sarco(endo)plasmic reticulum Ca2+-ATPases, leads to excessive diet-induced obesity and glucose intolerance in mice. However, it is unclear how loss of SLN per se affects muscle oxidative capacity and the ability of mitochondria to adapt to physiological stimuli, such as exercise training or calorie overload. To address this question, Sln–/– and wild-type (WT) littermates were given access to voluntar...
Source: Journal of Applied Physiology - May 18, 2017 Category: Physiology Authors: Gamu, D., Trinh, A., Fajardo, V. A., Bombardier, E., Tupling, A. R. Tags: RESEARCH ARTICLE Source Type: research
Effects of inspiratory muscle training on respiratory muscle electromyography and dyspnea during exercise in healthy men
We examined the effects of inspiratory muscle training (IMT) on dyspnea, EMGdi, and EMG of accessory inspiratory muscles. IMT significantly reduced submaximal dyspnea intensity ratings but did not change EMG of any inspiratory muscles. Improvements in exertional dyspnea following IMT may be the result of nonphysiological factors or physiological adaptations unrelated to neural respiratory drive. (Source: Journal of Applied Physiology)
Source: Journal of Applied Physiology - May 18, 2017 Category: Physiology Authors: Ramsook, A. H., Molgat-Seon, Y., Schaeffer, M. R., Wilkie, S. S., Camp, P. G., Reid, W. D., Romer, L. M., Guenette, J. A. Tags: RESEARCH ARTICLE Source Type: research
Cough physiology in elderly women with nontuberculous mycobacterial lung infections
This study investigates the cough motor response and cough sensitivity in patients with nontuberculous mycobacteria (NTM) infection. In elderly white female pulmonary NTM subjects, we demonstrated a capacity to produce coughs similar to that of age-matched control subjects but decreased cough sensitivity in response to a low dose of capsaicin compared with control subjects. These findings are important to understand the pathophysiological mechanisms resulting in NTM disease in elderly white women and/or the syndrome developing in elderly white female NTM patients. (Source: Journal of Applied Physiology)
Source: Journal of Applied Physiology - May 18, 2017 Category: Physiology Authors: Tsai, H.-W., Fennelly, K., Wheeler-Hegland, K., Adams, S., Condrey, J., Hosford, J. L., Davenport, P. W. Tags: RESEARCH ARTICLE Source Type: research
Anthropometric prediction of skeletal muscle cross-sectional area in persons with spinal cord injury
This study used anthropometric measurements and magnetic resonance imaging (MRI) to evaluate muscle cross-sectional area (CSA) and developed a field equation to predict thigh muscle CSA specific to the spinal cord-injured (SCI) population. Anthropometric measurements were correlated to the whole thigh CSA and muscle CSA as measured by MRI. The correlations led to the development of a SCI-specific field equation that accounted for intramuscular fat and bone areas. (Source: Journal of Applied Physiology)
Source: Journal of Applied Physiology - May 18, 2017 Category: Physiology Authors: Wade, R. C., Gorgey, A. S. Tags: RESEARCH ARTICLE Source Type: research
B-type natriuretic peptide increases cortisol and catecholamine concentrations in healthy subjects
B-type natriuretic peptide (BNP) is a hormone released by the heart in response to volume load and exerts natriuretic properties. It is clinically used as a diagnostic and prognostic biomarker and investigated as a pharmacological agent in the therapy of heart failure. Here we investigate the changes in pituitary, adrenal, and thyroid hormones in response to BNP administration in a randomized single-blinded crossover study conducted in ten healthy men aged 21–29 yr. Participants received in two study sessions a continuous intravenous infusion during 4 h (once placebo and once 3 pmol·kg–1·min&ndash...
Source: Journal of Applied Physiology - May 18, 2017 Category: Physiology Authors: Grimm, G., Resl, M., Heinisch, B. B., Hülsmann, M., Luger, A., Clodi, M., Vila, G. Tags: RESEARCH ARTICLE Source Type: research
Cardiorespiratory fitness modulates the acute flow-mediated dilation response following high-intensity but not moderate-intensity exercise in elderly men
This study is the first to show that moderate-intensity continuous cycling exercise increased flow-mediated dilation (FMD) transiently before normalization of FMD after 1 h, irrespective of cardiorespiratory fitness level in elderly men. Interestingly, we show increased FMD after high-intensity cycling exercise in higher fit men, with a sustained reduction in FMD in lower fit men. The prolonged reduction in FMD after high-intensity cycling exercise may be associated with future vascular adaptation but may also reflect a period of increased cardiovascular risk in lower fit elderly men. (Source: Journal of Applied Physiology)
Source: Journal of Applied Physiology - May 18, 2017 Category: Physiology Authors: Bailey, T. G., Perissiou, M., Windsor, M., Russell, F., Golledge, J., Green, D. J., Askew, C. D. Tags: RESEARCH ARTICLE Source Type: research
Normalization of hemoglobin-based oxygen carrier-201 induced vasoconstriction: targeting nitric oxide and endothelin
In conclusion, the pressor response to HBOC-201 is mediated by vasoconstriction due to NO scavenging and production of ET. Further research should explore the effect of longer-acting ET receptor blockers to counteract the side effect of hemoglobin-based oxygen carriers.
NEW & NOTEWORTHY Hemoglobin-based oxygen carrier (HBOC)-201 can disrupt hemodynamic homeostasis, mimicking some aspects of endothelial dysfunction, resulting in elevated systemic and pulmonary blood pressures. HBOC-201-induced vasoconstriction is mediated by scavenging nitric oxide (NO) and by upregulating endothelin (ET) production. Pressor effects can...
Source: Journal of Applied Physiology - May 18, 2017 Category: Physiology Authors: Taverne, Y. J., de Wijs-Meijler, D., te Lintel Hekkert, M., Moon-Massat, P. F., Dube, G. P., Duncker, D. J., Merkus, D. Tags: RESEARCH ARTICLE Source Type: research
Active shortening protects against stretch-induced force deficits in human skeletal muscle
This study indicates that velocity-controlled modulation of the number of strongly bound crossbridges is the basis for the observed relationship between stretch-induced muscle damage and prevailing shortening velocity. (Source: Journal of Applied Physiology)
Source: Journal of Applied Physiology - May 18, 2017 Category: Physiology Authors: Saripalli, A. L., Sugg, K. B., Mendias, C. L., Brooks, S. V., Claflin, D. R. Tags: RESEARCH ARTICLE Source Type: research
Skeletal muscle bioenergetics during all-out exercise: mechanistic insight into the oxygen uptake slow component and neuromuscular fatigue
In conclusion, the all-out exercise protocol utilized in the present study elicited a "slow component-like" increase in intramuscular ATPOX gain as well as a progressive increase in the phosphate cost of contraction. Furthermore, the development of peripheral fatigue was closely related to the perturbation of specific fatigue-inducing intramuscular factors (i.e., pH and H2PO4– concentration).
NEW & NOTEWORTHY The physiological mechanisms and skeletal muscle bioenergetics underlying all-out exercise performance are unclear. This study revealed an increase in oxidative ATP synthesis rate gain and the ATP cost of co...
Source: Journal of Applied Physiology - May 18, 2017 Category: Physiology Authors: Broxterman, R. M., Layec, G., Hureau, T. J., Amann, M., Richardson, R. S. Tags: RESEARCH ARTICLE Source Type: research
Thermoregulatory responses to exercise at a fixed rate of heat production are not altered by acute hypoxia
This study sought to assess the within-subject influence of acute hypoxia on exercise-induced changes in core temperature and sweating. Eight participants [1.75 (0.06) m, 70.2 (6.8) kg, 25 (4) yr, 54 (8) ml·kg–1·min–1] completed 45 min of cycling, once in normoxia (NORM; FIO2 = 0.21) and twice in hypoxia (HYP1/HYP2; FIO2= 0.13) at 34.4(0.2)°C, 46(3)% RH. These trials were designed to elicit 1) two distinctly different %Vo2peak [NORM: 45 (8)% and HYP1: 62 (7)%] at the same heat production (Hprod) [NORM: 6.7 (0.6) W/kg and HYP1: 7.0 (0.5) W/kg]; and 2) the same %Vo2peak [NORM: 45 (8)% and HYP2: ...
Source: Journal of Applied Physiology - May 18, 2017 Category: Physiology Authors: Coombs, G. B., Cramer, M. N., Ravanelli, N., Imbeault, P., Jay, O. Tags: RESEARCH ARTICLE Source Type: research
Two weeks of moderate-intensity continuous training, but not high-intensity interval training, increases insulin-stimulated intestinal glucose uptake
This study shows that already 2 wk of MICT enhances insulin-stimulated glucose uptake, while both training modes reduce fasting free fatty acid uptake in the intestine in healthy, middle-aged men, providing an additional mechanism by which exercise training can improve whole body metabolism.
NEW & NOTEWORTHY This is the first study where the effects of exercise training on the intestinal substrate uptake have been investigated using the most advanced techniques available. We also show the importance of exercise intensity in inducing these changes. (Source: Journal of Applied Physiology)
Source: Journal of Applied Physiology - May 9, 2017 Category: Physiology Authors: Motiani, K. K., Savolainen, A. M., Eskelinen, J.-J., Toivanen, J., Ishizu, T., Yli-Karjanmaa, M., Virtanen, K. A., Parkkola, R., Kapanen, J., Grönroos, T. J., Haaparanta-Solin, M., Solin, O., Savisto, N., Ahotupa, M., Löyttyniemi, E., Knuu Tags: RESEARCH ARTICLE Source Type: research
Exertional dyspnea associated with chest wall strapping is reduced when external dead space substitutes for part of the exercise stimulus to ventilation
This study examined the hypothesis that dyspnea with restriction depends principally on the degree of reflex ventilatory stimulation. We compared dyspnea at the same (iso)ventilation when added dead space provided a component of the ventilatory stimulus during exercise. Eleven healthy men undertook a randomized controlled crossover trial that compared four constant work exercise conditions: 1) control (CTRL): unrestricted breathing at 90% gas exchange threshold (GET); 2) CTRL+dead space (DS): unrestricted breathing with 0.6-l dead space, at isoventilation to CTRL due to reduced exercise intensity; 3) CWS: chest wall strapp...
Source: Journal of Applied Physiology - May 9, 2017 Category: Physiology Authors: Garske, L. A., Lal, R., Stewart, I. B., Morris, N. R., Cross, T. J., Adams, L. Tags: RESEARCH ARTICLE Source Type: research
