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Neural Plasticity 2016When people focus attention or carry out a demanding task, their breathing changes. But which parameters of respiration vary exactly and can respiration reliably be used... (Review)
Review
When people focus attention or carry out a demanding task, their breathing changes. But which parameters of respiration vary exactly and can respiration reliably be used as an index of cognitive load? These questions are addressed in the present systematic review of empirical studies investigating respiratory behavior in response to cognitive load. Most reviewed studies were restricted to time and volume parameters while less established, yet meaningful parameters such as respiratory variability have rarely been investigated. The available results show that respiratory behavior generally reflects cognitive processing and that distinct parameters differ in sensitivity: While mentally demanding episodes are clearly marked by faster breathing and higher minute ventilation, respiratory amplitude appears to remain rather stable. The present findings further indicate that total variability in respiratory rate is not systematically affected by cognitive load whereas the correlated fraction decreases. In addition, we found that cognitive load may lead to overbreathing as indicated by decreased end-tidal CO2 but is also accompanied by elevated oxygen consumption and CO2 release. However, additional research is needed to validate the findings on respiratory variability and gas exchange measures. We conclude by outlining recommendations for future research to increase the current understanding of respiration under cognitive load.
Topics: Animals; Attention; Cognition; Humans; Oxygen Consumption; Psychomotor Performance; Respiratory Mechanics; Tidal Volume
PubMed: 27403347
DOI: 10.1155/2016/8146809 -
European Journal of Applied Physiology Jun 2023The purpose of this study was to investigate to what extent aerobic power (MAP), maximal anaerobic power (MANP), anaerobic capacity measured as time to exhaustion at...
The purpose of this study was to investigate to what extent aerobic power (MAP), maximal anaerobic power (MANP), anaerobic capacity measured as time to exhaustion at 130% MAP (TTE), and maximal accumulated oxygen deficit (MAOD) correlated with 800 m double poling time trial performance (800TT) in a ski ergometer. A second aim was to investigate the relationship between TTE and MAOD, and to what extent TTE and MAOD would relate to anaerobic power reserve (APR). Eighteen cross-country skiers were tested for peak oxygen uptake (VO) and oxygen cost of double poling to assess MAP. Peak power measurements during a 100 m TT were performed to assess MANP. TTE and an 800TT with continuous VO measurements were performed to assess time performance and MAOD. All tests were performed on a ski ergometer. Both MAP and MANP correlated strongly (r = - 0.936 and - 0.922, respectively, p < 0.01) with 800TT. Neither TTE nor MAOD correlated with 800TT. TTE correlated moderately with MAOD, both in mL kg and in %VO (r = 0.559, p < 0.05 and 0.621, p < 0.01, respectively). Both TTE and MAOD seemed to be a product of APR. These results suggest focusing on MAP and MANP, but not anaerobic capacity to explain time performance in an event with approximately 3 min duration.
Topics: Humans; Oxygen Consumption; Ergometry; Oxygen; Anaerobic Threshold; Exercise Test
PubMed: 36750479
DOI: 10.1007/s00421-023-05149-9 -
International Journal of Sports... Nov 2023One hundred years ago, Hill and Lupton introduced the concept of maximal oxygen uptake (V˙O2max), which is regarded as "the principal progenitor of sports physiology."...
One hundred years ago, Hill and Lupton introduced the concept of maximal oxygen uptake (V˙O2max), which is regarded as "the principal progenitor of sports physiology." We provide a succinct overview of the evolvement of research on V˙O2max, from Hill and Lupton's initial findings to current debates on limiting factors for V˙O2max and the associated role of convective and diffusive components. Furthermore, we update the current use of V˙O2max in elite endurance sport and clinical settings. Practical Applications and Conclusions: V˙O2max is a healthy and active centenarian that remains a very important measure in elite endurance sports and additionally contributes as an important vital sign of cardiovascular function and fitness in clinical settings. Over the past 100 years, guidelines for the test protocols and exhaustion criteria, as well as the understanding of limiting factors for V˙O2max, have improved dramatically. Presently, possibilities of accurate and noninvasive determination of the convective versus diffusive components of V˙O2max by wearable sensors represent an important future application. V˙O2max is not only an indicator of cardiorespiratory function, fitness, and endurance performance but also represents an important biomarker of cardiovascular function and health to be included in routine assessment in clinical practice.
Topics: Humans; Aged, 80 and over; Exercise Test; Oxygen Consumption; Physical Endurance; Exercise; Sports
PubMed: 37770066
DOI: 10.1123/ijspp.2023-0229 -
The Journal of Physiology Apr 2022Coronary blood flow is tightly regulated to ensure that myocardial oxygen delivery meets local metabolic demand via the concurrent action of myogenic, neural and...
Coronary blood flow is tightly regulated to ensure that myocardial oxygen delivery meets local metabolic demand via the concurrent action of myogenic, neural and metabolic mechanisms. Although several competing hypotheses exist, the specific nature of the local metabolic mechanism(s) remains poorly defined. To gain insights into the viability of putative metabolic feedback mechanisms and into the co-ordinated action of parallel regulatory mechanisms, we applied a multiscale modelling framework to analyse experimental data on coronary pressure, flow and myocardial oxygen delivery in the porcine heart in vivo. The modelling framework integrates a previously established lumped-parameter model of myocardial perfusion used to account for transmural haemodynamic variations and a simple vessel mechanics model used to simulate the vascular tone in each of three myocardial layers. Vascular tone in the resistance vessel mechanics model is governed by input stimuli from the myogenic, metabolic and autonomic control mechanisms. Seven competing formulations of the metabolic feedback mechanism are implemented in the modelling framework, and associated model simulations are compared with experimental data on coronary pressures and flows under a range of experimental conditions designed to interrogate the governing control mechanisms. Analysis identifies a maximally probable metabolic mechanism among the seven tested models, in which production of a metabolic signalling factor is proportional to myocardial oxygen consumption and delivery is proportional to flow. Finally, the identified model is validated based on comparisons of simulations with data on the myocardial perfusion response to conscious exercise that were not used for model identification. KEY POINTS: Although several competing hypotheses exist, we lack knowledge of specific nature of the metabolic mechanism(s) governing regional myocardial perfusion. Moreover, we lack an understanding of how parallel myogenic, adrenergic/autonomic and metabolic mechanisms work together to regulatory oxygen delivery in the beating heart. We have developed a multiscale modelling framework to test competing hypotheses against experimental data on coronary pressure, flow and myocardial oxygen delivery in the porcine heart in vivo. The analysis identifies a maximally probable metabolic mechanism among seven tested models, in which the production of a metabolic signalling factor is proportional to myocardial oxygen consumption and delivery is proportional to flow.
Topics: Animals; Coronary Circulation; Feedback; Hemodynamics; Myocardium; Oxygen; Oxygen Consumption; Perfusion; Swine
PubMed: 35156733
DOI: 10.1113/JP282237 -
The Journal of Physiology Apr 2016
Topics: Aging; Humans; Muscle, Skeletal; Oxygen; Oxygen Consumption
PubMed: 27079630
DOI: 10.1113/JP272062 -
BMC Genomics Nov 2017Cardiorespiratory fitness (VO) is an excellent predictor of chronic disease morbidity and mortality risk. Guidelines recommend individuals undertake exercise training to... (Review)
Review
BACKGROUND
Cardiorespiratory fitness (VO) is an excellent predictor of chronic disease morbidity and mortality risk. Guidelines recommend individuals undertake exercise training to improve VO for chronic disease reduction. However, there are large inter-individual differences between exercise training responses. This systematic review is aimed at identifying genetic variants that are associated with VO trainability.
METHODS
Peer-reviewed research papers published up until October 2016 from four databases were examined. Articles were included if they examined genetic variants, incorporated a supervised aerobic exercise intervention; and measured VO/VO pre and post-intervention.
RESULTS
Thirty-five articles describing 15 cohorts met the criteria for inclusion. The majority of studies used a cross-sectional retrospective design. Thirty-two studies researched candidate genes, two used Genome-Wide Association Studies (GWAS), and one examined mRNA gene expression data, in addition to a GWAS. Across these studies, 97 genes to predict VO trainability were identified. Studies found phenotype to be dependent on several of these genotypes/variants, with higher responders to exercise training having more positive response alleles than lower responders (greater gene predictor score). Only 13 genetic variants were reproduced by more than two authors. Several other limitations were noted throughout these studies, including the robustness of significance for identified variants, small sample sizes, limited cohorts focused primarily on Caucasian populations, and minimal baseline data. These factors, along with differences in exercise training programs, diet and other environmental gene expression mediators, likely influence the ideal traits for VO trainability.
CONCLUSION
Ninety-seven genes have been identified as possible predictors of VO trainability. To verify the strength of these findings and to identify if there are more genetic variants and/or mediators, further tightly-controlled studies that measure a range of biomarkers across ethnicities are required.
Topics: Cardiorespiratory Fitness; Exercise; Genotyping Techniques; Humans; Oxygen Consumption
PubMed: 29143670
DOI: 10.1186/s12864-017-4192-6 -
Journal of the American Heart... Jul 2023Background An elevated ventilatory efficiency slope during exercise (minute ventilation/volume of expired CO; V/VCO slope) is a strong prognostic indicator in heart...
Background An elevated ventilatory efficiency slope during exercise (minute ventilation/volume of expired CO; V/VCO slope) is a strong prognostic indicator in heart failure. It is elevated in people with heart failure with preserved ejection, many of whom have hypertension. However, whether the V/VCO slope is also elevated in people with primary hypertension versus normotensive individuals is unknown. We hypothesize that there is a spectrum of ventilatory inefficiency in cardiovascular disease, reflecting an increasingly abnormal physiological response to exercise. The aim of this study was to evaluate the V/VCO slope in patients with hypertension compared with age-, peak oxygen consumption-, and sex-matched healthy subjects. Methods and Results Ramped cardiovascular pulmonary exercise tests to peak oxygen consumption were completed on a bike ergometer in 55 patients with primary hypertension and 24 normotensive controls. The V/VCO slope was assessed from the onset of exercise to peak oxygen consumption. Data were compared using unpaired Student test. Age (mean±SD, 66±6 versus 64±6 years; =0.18), body mass index (25.4±3.5 versus 24±2.4 kg/m; =0.13), and peak oxygen consumption (23.2±6.6 versus 24±7.3 mL/min per kg; =0.64) were similar between groups. The V/VCO slope was elevated in the hypertensive group versus controls (31.8±4.5 versus 28.4±3.4; =0.002). Only 27% of the hypertensive group were classified as having a normal V/VCO slope (20-30) versus 71% in the control group. Conclusions Ventilatory efficiency is impaired people with hypertension without a diagnosis of heart failure versus normotensive individuals. Future research needs to establish whether those patients with hypertension with elevated V/VCO slopes are at risk of developing future heart failure.
Topics: Humans; Middle Aged; Aged; Oxygen Consumption; Lung; Prognosis; Exercise Test; Heart Failure; Hypertension; Essential Hypertension; Exercise Tolerance
PubMed: 37345800
DOI: 10.1161/JAHA.121.024335 -
European Journal of Applied Physiology Nov 2023To compare physiological responses between a self-paced 4-min double-poling (DP) time-trial (TT) versus a 4-min diagonal-stride (DS) time-trial (TT). The relative...
PURPOSE
To compare physiological responses between a self-paced 4-min double-poling (DP) time-trial (TT) versus a 4-min diagonal-stride (DS) time-trial (TT). The relative importance of peak oxygen uptake ([Formula: see text]O), anaerobic capacity, and gross efficiency (GE) for projection of 4-min TT and TT roller-skiing performances were also examined.
METHODS
Sixteen highly trained male cross-country skiers performed, in each sub-technique on separate occasions, an 8 × 4-min incremental submaximal protocol, to assess individual metabolic rate (MR) versus power output (PO) relationships, followed by a 10-min passive break and then the TT or TT, with a randomized order between sub-techniques.
RESULTS
In comparison to TT, the TT resulted in 10 ± 7% lower total MR, 5 ± 4% lower aerobic MR, 30 ± 37% lower anaerobic MR, and 4.7 ± 1.2 percentage points lower GE, which resulted in a 32 ± 4% lower PO (all P < 0.01). The [Formula: see text]O and anaerobic capacity were 4 ± 4% and 30 ± 37% lower, respectively, in DP than DS (both P < 0.01). The PO for the two time-trial (TT) performances were not significantly correlated (R = 0.044). Similar parabolic pacing strategies were used during both TTs. Multivariate data analysis projected TT performance using [Formula: see text]O, anaerobic capacity, and GE (TT, R = 0.974; TT, R = 0.848). The variable influence on projection values for [Formula: see text]O, anaerobic capacity, and GE were for TT, 1.12 ± 0.60, 1.01 ± 0.72, and 0.83 ± 0.38, respectively, and TT, 1.22 ± 0.35, 0.93 ± 0.44, and 0.75 ± 0.19, respectively.
CONCLUSIONS
The results show that a cross-country skier's "metabolic profile" and performance capability are highly sub-technique specific and that 4-min TT performance is differentiated by physiological factors, such as [Formula: see text]O, anaerobic capacity, and GE.
Topics: Humans; Male; Athletic Performance; Oxygen Consumption; Skiing; Exercise Test
PubMed: 37302104
DOI: 10.1007/s00421-023-05239-8 -
Sports Medicine (Auckland, N.Z.) Feb 2024Sex differences in physiological responses to various stressors, including exercise, have been well documented. However, the specific impact of these differences on... (Review)
Review
Sex differences in physiological responses to various stressors, including exercise, have been well documented. However, the specific impact of these differences on exposure to hypoxia, both at rest and during exercise, has remained underexplored. Many studies on the physiological responses to hypoxia have either excluded women or included only a limited number without analyzing sex-related differences. To address this gap, this comprehensive review conducted an extensive literature search to examine changes in physiological functions related to oxygen transport and consumption in hypoxic conditions. The review encompasses various aspects, including ventilatory responses, cardiovascular adjustments, hematological alterations, muscle metabolism shifts, and autonomic function modifications. Furthermore, it delves into the influence of sex hormones, which evolve throughout life, encompassing considerations related to the menstrual cycle and menopause. Among these physiological functions, the ventilatory response to exercise emerges as one of the most sex-sensitive factors that may modify reactions to hypoxia. While no significant sex-based differences were observed in cardiac hemodynamic changes during hypoxia, there is evidence of greater vascular reactivity in women, particularly at rest or when combined with exercise. Consequently, a diffusive mechanism appears to be implicated in sex-related variations in responses to hypoxia. Despite well-established sex disparities in hematological parameters, both acute and chronic hematological responses to hypoxia do not seem to differ significantly between sexes. However, it is important to note that these responses are sensitive to fluctuations in sex hormones, and further investigation is needed to elucidate the impact of the menstrual cycle and menopause on physiological responses to hypoxia.
Topics: Humans; Female; Male; Altitude; Hypoxia; Exercise; Gonadal Steroid Hormones; Heart; Oxygen Consumption
PubMed: 37902936
DOI: 10.1007/s40279-023-01954-6 -
Cell Metabolism Jul 2015
Topics: Animals; Exercise; Health; Humans; Metabolism; Oxygen Consumption
PubMed: 26366447
DOI: 10.1016/j.cmet.2015.06.012