Ventricular action potential adaptation to regular exercise: role of {beta}-adrenergic and KATP channel function
Regular exercise training is known to affect the action potential duration (APD) and improve heart function, but involvement of β-adrenergic receptor (β-AR) subtypes and/or the ATP-sensitive K+ (KATP) channel is unknown. To address this, female and male Sprague-Dawley rats were randomly assigned to voluntary wheel-running or control groups; they were anesthetized after 6–8 wk of training, and myocytes were isolated. Exercise training significantly increased APD of apex and base myocytes at 1 Hz and decreased APD at 10 Hz. Ca2+ transient durations reflected the changes in APD, while Ca2+ transient amplitudes...
Source: Journal of Applied Physiology - August 1, 2017 Category: Physiology Authors: Wang, X., Fitts, R. H. Tags: RESEARCH ARTICLE Source Type: research
Effect of exercise timing on elevated postprandial glucose levels
There is no consensus regarding optimal exercise timing for reducing postprandial glucose (PPG). The purpose of the present study was to determine the most effective exercise timing. Eleven participants completed four different exercise patterns 1) no exercise; 2) preprandial exercise (jogging); 3) postprandial exercise; and 4) brief periodic exercise intervention (three sets of 1-min jogging + 30 s of rest, every 30 min, 20 times total) in a random order separated by a minimum of 5 days. Preprandial and postprandial exercise consisted of 20 sets of intermittent exercise (1 min of jogging + 30 s rest per set) repeated 3 ti...
Source: Journal of Applied Physiology - August 1, 2017 Category: Physiology Authors: Hatamoto, Y., Goya, R., Yamada, Y., Yoshimura, E., Nishimura, S., Higaki, Y., Tanaka, H. Tags: RESEARCH ARTICLE Source Type: research
Edmund Goodwyn and the first description of diving bradycardia
Diving bradycardia is a primordial oxygen-conserving reflex by which the heart rate of air-breathing vertebrates, including humans, slows down in response to water immersion. Its discovery is attributed to Paul Bert, whose seminal observation was published in 1870 as part of a series of experiments that examined physiological adaptations to asphyxia in ducks and other animals. However, Edmund Goodwyn, a British physician who studied medicine at the University of Edinburgh, had already described this reflex in his doctoral thesis, which was originally published in Latin in 1786 and again in English in 1788. Ironically, even...
Source: Journal of Applied Physiology - August 1, 2017 Category: Physiology Authors: Vega, J. L. Tags: REVIEW Source Type: research
Influence of maximal fat oxidation on long-term weight loss maintenance in humans
Impaired maximal fat oxidation has been linked to obesity and weight regain after weight loss. The aim was to investigate the relationship between maximal fat oxidation (MFO) and long-term weight loss maintenance. Eighty subjects [means (SD): age, 36(13) yrs; BMI, 38(1) kg/m2] were recruited from a total of 2,420 former participants of an 11- to 12-wk lifestyle intervention. Three groups were established based on percent weight loss at follow-up [5.3(3.3) yr]: clinical weight loss maintenance (CWL), >10% weight loss; moderate weight loss (MWL), 1–10% weight loss; and weight regain (WR). Body composition (dual X-ra...
Source: Journal of Applied Physiology - July 19, 2017 Category: Physiology Authors: Dandanell, S., Husted, K., Amdisen, S., Vigelso, A., Dela, F., Larsen, S., Helge, J. W. Tags: RESEARCH ARTICLE Source Type: research
Lower-body negative pressure decreases noninvasively measured intracranial pressure and internal jugular vein cross-sectional area during head-down tilt
Long-term spaceflight induces a near visual acuity change in ~50% of astronauts. In some crew members, postflight cerebrospinal fluid (CSF) opening pressures by lumbar puncture are as high as 20.9 mmHg; these members demonstrated optic disc edema. CSF communicates through the cochlear aqueduct to affect perilymphatic pressure and tympanic membrane motion. We hypothesized that 50 mmHg of lower-body negative pressure (LBNP) during 15° head-down tilt (HDT) would mitigate elevations in internal jugular vein cross-sectional area (IJV CSA) and intracranial pressure (ICP). Fifteen healthy adult volunteers were positioned in s...
Source: Journal of Applied Physiology - July 19, 2017 Category: Physiology Authors: Watkins, W., Hargens, A. R., Seidl, S., Clary, E. M., Macias, B. R. Tags: RESEARCH ARTICLE Source Type: research
Obesity-induced discrepancy between contractile and metabolic phenotypes in slow- and fast-twitch skeletal muscles of female obese Zucker rats
This study describes fiber-type characteristics (size, proportions, and oxidative enzyme activity) in two typical hindlimb muscles with opposite structure and function in an animal model of genetic obesity. Lesser fiber diameter, fiber-type composition, and histochemical succinic dehydrogenase activity (an oxidative marker) of muscle fiber types were assessed in slow (soleus)- and fast (tibialis cranialis)-twitch muscles of obese Zucker rats and compared with age (16 wk)- and sex (females)-matched lean Zucker rats (n = 16/group). Muscle mass and lesser fiber diameter were lower in both muscle types of obese compared with l...
Source: Journal of Applied Physiology - July 19, 2017 Category: Physiology Authors: Acevedo, L. M., Raya, A. I., Rios, R., Aguilera-Tejero, E., Rivero, J.-L. L. Tags: RESEARCH ARTICLE Source Type: research
Exercise training and metformin, but not exercise training alone, decreases insulin production and increases insulin clearance in adults with prediabetes
In this study, metformin combined with exercise training reduced circulating proinsulin, and both groups taking metformin increased insulin clearance. This suggests that adding metformin to exercise may augment or attenuate training effects depending on the outcome or organ system being assessed.
NEW & NOTEWORTHY Exercise is increasingly viewed as medication, creating a need to understand its interactions with other common medications. Research suggests metformin, a widely prescribed diabetes medication, may diminish the benefits of exercise when used in combination. In this study, however, metformin combined with exer...
Source: Journal of Applied Physiology - July 18, 2017 Category: Physiology Authors: Viskochil, R., Malin, S. K., Blankenship, J. M., Braun, B. Tags: RESEARCH ARTICLE Source Type: research
Data collection, handling, and fitting strategies to optimize accuracy and precision of oxygen uptake kinetics estimation from breath-by-breath measurements
This study identified an unbiased method for data collection, handling, and fitting to optimize Vo2P kinetics estimation. A validated computational model of Vo2P kinetics and a Monte Carlo approach simulated 2 x 105 moderate-intensity transitions using a distribution of metabolic and circulatory parameters spanning normal health. Effects of averaging (interpolation, binning, stacking, or separate fitting of up to 10 transitions) and fitting procedures (biexponential fitting, or 2 isolation by time removal, statistical, or derivative methods followed by monoexponential fitting) on accuracy and precision of Vo2P kinetics est...
Source: Journal of Applied Physiology - July 18, 2017 Category: Physiology Authors: Benson, A. P., Bowen, T. S., Ferguson, C., Murgatroyd, S. R., Rossiter, H. B. Tags: RESEARCH ARTICLE Source Type: research
Biomechanical impact of provisional stenting and balloon dilatation on coronary bifurcation: clinical implications
In-stent restenosis (ISR) and stent thrombosis remain clinically significant problems for bifurcations. Although the role of wall shear stress (WSS) has been well investigated, the role of circumferential wall stresses (CWS) has not been well studied in provisional stenting with and without final kissing balloon (FKB). We hypothesized that the perturbation of CWS at the SB in provisional stenting and balloon dilatation is an important factor in addition to WSS, and, hence, may affect restenosis rates (i.e., higher CWS correlates with higher restenosis). To test this hypothesis, we developed computational models of stent, F...
Source: Journal of Applied Physiology - July 18, 2017 Category: Physiology Authors: Chen, H. Y., Al-Saadon, K., Louvard, Y., Kassab, G. S. Tags: RESEARCH ARTICLE Source Type: research
Dispelling the myth that habitual caffeine consumption influences the performance response to acute caffeine supplementation
This study investigates the influence of habitual caffeine intake on aerobic exercise-performance responses to acute caffeine supplementation. A double-blind, crossover, counterbalanced study was performed. Forty male endurance-trained cyclists were allocated into tertiles, according to their daily caffeine intake: low (58 ± 29 mg/d), moderate (143 ± 25 mg/d), and high (351 ± 139 mg/d) consumers. Participants completed three trials in which they performed simulated cycling time trials (TTs) in the fastest time possible following ingestion of the following: caffeine (CAF: 6 mg/kg body mass), placebo (PL...
Source: Journal of Applied Physiology - July 18, 2017 Category: Physiology Authors: Goncalves, L. d. S., Painelli, V. d. S., Yamaguchi, G., Oliveira, L. F. d., Saunders, B., da Silva, R. P., Maciel, E., Artioli, G. G., Roschel, H., Gualano, B. Tags: RESEARCH ARTICLE Source Type: research
Experimental dyspnea as a stressor: differential cardiovegetative responses to inspiratory threshold loading in healthy men and women
Dyspnea is associated with an emotional reaction that involves limbic activation. The inspiratory threshold load (ITL) is known to elicit a dyspneic response in healthy subjects. Laboratory-induced stress conditions have been shown to elicit sex-related differences in cardiovascular responses. The aim of this study was to evaluate how healthy men (n = 8) and women (n = 9) react and adapt to 5-min periods of ITL at three levels (low, medium, and high) in terms of heart rate (HR), temporal (RMSSD) and spectral (LF, HF, LF/HF ratio) HRV indexes, and rating of breathing discomfort. HR increased with low, medium, and high ITL i...
Source: Journal of Applied Physiology - July 18, 2017 Category: Physiology Authors: Nierat, M.-C., Laviolette, L., Hudson, A., Similowski, T., Sevoz-Couche, C. Tags: RESEARCH ARTICLE Source Type: research
Effect of cyclooxygenase inhibition on the inspiratory muscle metaboreflex-induced cardiovascular consequences in men
Inspiratory muscle metaboreflex activation increases mean arterial pressure (MAP) and limb vascular resistance (LVR) and decreases limb blood flow (QL). Cyclooxygenase (COX) inhibition has been found to attenuate limb skeletal muscle metaboreflex-induced increases in muscle sympathetic nerve activity. We hypothesized that compared with placebo (PLA), COX inhibition would attenuate inspiratory muscle metaboreflex-induced 1) increases in MAP and LVR and 2) decreases in QL. Seven men (22 ± 1 yr) were recruited and orally consumed ibuprofen (IB; 10 mg/kg) or PLA 90 min before performing the cold pressor test (CPT) for 2...
Source: Journal of Applied Physiology - July 18, 2017 Category: Physiology Authors: Smith, J. R., Didier, K. D., Hammer, S. M., Alexander, A. M., Kurti, S. P., Copp, S. W., Barstow, T. J., Harms, C. A. Tags: RESEARCH ARTICLE Source Type: research
Lower limb explosive strength capacity in elderly women: effects of resistance training and healthy diet
In conclusion, a healthy diet rich in n-3 PUFA can optimize the effects of resistance training on dynamic explosive strength capacity during isolated lower limb movements and multijoint exercises in healthy elderly women.
NEW & NOTEWORTHY Age-related decline in lower limb explosive strength leads to impaired ability to perform daily living tasks. The present randomized controlled trial demonstrates that a healthy diet rich in n-3 polyunsaturated fatty acid (n-3 PUFA) enhances resistance training-induced gains in dynamic explosive strength capacity during isolated lower limb movements and multijoint exercises in healthy...
Source: Journal of Applied Physiology - July 18, 2017 Category: Physiology Authors: Edholm, P., Strandberg, E., Kadi, F. Tags: RESEARCH ARTICLE Source Type: research
Evidence for {beta}-adrenergic modulation of sweating during incremental exercise in habitually trained males
The aim of the present study was to determine the β-adrenergic contribution to sweating during incremental exercise in habitually trained males. Nine habitually trained and 11 untrained males performed incremental cycling until exhaustion (20 W/min). Bilateral forearm sweat rates (ventilated capsule) were measured at two skin sites that were transdermally administered via iontophoresis with either 1% propranolol (Propranolol, a nonselective β-adrenergic receptor antagonist) or saline (Control). The sweat rate was evaluated as a function of both relative (percentage of maximum workload) and absolute exercise inten...
Source: Journal of Applied Physiology - July 18, 2017 Category: Physiology Authors: Amano, T., Shitara, Y., Fujii, N., Inoue, Y., Kondo, N. Tags: RESEARCH ARTICLE Source Type: research
Progression and variability of physiologic deterioration in an ovine model of lung infection sepsis
In this study, a lung infection model of pneumonia in sheep (n = 12) that included smoke inhalation injury followed by methicillin-resistant Staphylococcus aureus placement into the lungs was used to investigate hemodynamic and pulmonary dysfunctions during the course of sepsis progression. To assess the variability in disease progression, animals were retrospectively divided into survivor (n = 6) and nonsurvivor (n = 6) groups, and a range of physiological indexes reflecting hemodynamic and pulmonary function were estimated and compared to evaluate variability in dynamics underlying sepsis development. Blood pressure and ...
Source: Journal of Applied Physiology - July 18, 2017 Category: Physiology Authors: Yaghouby, F., Daluwatte, C., Fukuda, S., Nelson, C., Salsbury, J., Kinsky, M., Kramer, G. C., Strauss, D. G., Enkhbaatar, P., Scully, C. G. Tags: RESEARCH ARTICLE Source Type: research
