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Ventilatory threshold

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https://www.readbyqxmd.com/read/28819793/the-mechanisms-underlying-the-production-of-discontinuous-gas-exchange-cycles-in-insects
#1
REVIEW
Philip G D Matthews
This review examines the control of gas exchange in insects, specifically examining what mechanisms could explain the emergence of discontinuous gas exchange cycles (DGCs). DGCs are gas exchange patterns consisting of alternating breath-hold periods and bouts of gas exchange. While all insects are capable of displaying a continuous pattern of gas exchange, this episodic pattern is known to occur within only some groups of insects and then only sporadically or during certain phases of their life cycle. Investigations into DGCs have tended to emphasise the role of chemosensory thresholds in triggering spiracle opening as critical for producing these gas exchange patterns...
August 17, 2017: Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology
https://www.readbyqxmd.com/read/28818154/physiology-based-modeling-may-predict-surgical-treatment-outcome-for-obstructive-sleep-apnea
#2
Yanru Li, Jingying Ye, Demin Han, Xin Cao, Xiu Ding, Yuhuan Zhang, Wen Xu, Jeremy Orr, Rachel Jen, Scott Sands, Atul Malhotra, Robert Owens
STUDY OBJECTIVES: To test whether the integration of both anatomical and nonanatomical parameters (ventilatory control, arousal threshold, muscle responsiveness) in a physiology-based model will improve the ability to predict outcomes after upper airway surgery for obstructive sleep apnea (OSA). METHODS: In 31 patients who underwent upper airway surgery for OSA, loop gain and arousal threshold were calculated from preoperative polysomnography (PSG). Three models were compared: (1) a multiple regression based on an extensive list of PSG parameters alone; (2) a multivariate regression using PSG parameters plus PSG-derived estimates of loop gain, arousal threshold, and other trait surrogates; (3) a physiological model incorporating selected variables as surrogates of anatomical and nonanatomical traits important for OSA pathogenesis...
August 14, 2017: Journal of Clinical Sleep Medicine: JCSM: Official Publication of the American Academy of Sleep Medicine
https://www.readbyqxmd.com/read/28816504/validity-and-reliability-of-the-3-min-all-out-running-test-to-measure-critical-velocity-in-hot-environments
#3
Yu-Hsuan Kuo, Ching-Feng Cheng, Wei-Chieh Hsu, Del P Wong
This study's aim was to investigate the test-retest reliability of the 3-min all-out running test (3MRT) in hot environments. Twelve male sprinters (age 21.2 ± 1.8 years; height 1.78 ± 0.01 m; weight 71.0 ± 1.6 kg; [Formula: see text] 55.0 ± 1.0 mL kg(-1) min(-1)) performed an incremental exercise test in a laboratory, during which the first and second ventilatory thresholds (VT1 and VT2) and [Formula: see text] were determined. In addition, they performed two 3MRTs on an outdoor track in a hot environment, during which the critical velocity (CV) and anaerobic capacity (D') were estimated...
August 17, 2017: Research in Sports Medicine
https://www.readbyqxmd.com/read/28805258/impact-of-beta-blockers-on-cardiopulmonary-exercise-testing-in-patients-with-advanced-liver-disease
#4
M P Wallen, A Hall, K A Dias, J S Ramos, S E Keating, A J Woodward, T L Skinner, G A Macdonald, R Arena, J S Coombes
BACKGROUND: Patients with advanced liver disease may develop portal hypertension that can result in variceal haemorrhage. Beta-blockers reduce portal pressure and minimise haemorrhage risk. These medications may attenuate measures of cardiopulmonary performance, such as the ventilatory threshold and peak oxygen uptake measured via cardiopulmonary exercise testing. AIM: To determine the effect of beta-blockers on cardiopulmonary exercise testing variables in patients with advanced liver disease...
August 14, 2017: Alimentary Pharmacology & Therapeutics
https://www.readbyqxmd.com/read/28750585/nutritional-ketone-salts-increase-fat-oxidation-but-impair-high-intensity-exercise-performance-in-healthy-adult-males
#5
Trevor O'Malley, Etienne Myette-Cote, Cody Durrer, Jonathan P Little
This study investigated the impact of raising plasma beta-hydroxybutyrate (β-OHB) through ingestion of ketone salts on substrate oxidation and performance during cycling exercise. Ten healthy adult males (age, 23 ± 3 years; body mass index, 25 ± 3 kg/m(2), peak oxygen uptake, 45 ± 10 mL/(kg·min)(-1)) were recruited to complete 2 experimental trials. Before enrollment in the experimental conditions, baseline anthropometrics and cardiorespiratory fitness (peak oxygen uptake) were assessed and familiarization to the study protocol was provided...
July 27, 2017: Applied Physiology, Nutrition, and Metabolism, Physiologie Appliquée, Nutrition et Métabolisme
https://www.readbyqxmd.com/read/28744255/glycemic-and-metabolic-effects-of-two-long-bouts-of-moderate-intensity-exercise-in-men-with-normal-glucose-tolerance-or-type-2-diabetes
#6
Saeed Reza Eshghi, Kevin Fletcher, Étienne Myette-Côté, Cody Durrer, Raniah Q Gabr, Jonathan P Little, Peter Senior, Craig Steinback, Margie H Davenport, Gordon J Bell, Dion R Brocks, Normand G Boulé
BACKGROUND: The glycemic and insulinemic responses following 30-60 min of exercise have been extensively studied, and a dose-response has been proposed between exercise duration, or volume, and improvements in glucose tolerance or insulin sensitivity. However, few studies have examined the effects of longer bouts of exercise in type 2 diabetes (T2D). Longer bouts may have a greater potential to affect glucagon, interleukin-6 (IL-6) and incretin hormones [i.e., glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP)]...
2017: Frontiers in Endocrinology
https://www.readbyqxmd.com/read/28741667/an-evaluation-of-the-validity-of-the-pre-operative-oxygen-uptake-efficiency-slope-as-an-indicator-of-cardiorespiratory-fitness-in-elderly-patients-scheduled-for-major-colorectal-surgery
#7
B C Bongers, A E Berkel, J M Klaase, N L van Meeteren
This study aimed to investigate the validity of the oxygen uptake efficiency slope as an objective and submaximal indicator of cardiorespiratory fitness in elderly patients scheduled for major colorectal surgery. Patients ≥ 60 years of age, with a metabolic equivalent score using the Veterans Activity Questionnaire ≤ 7 and scheduled for major colorectal surgery participated in a pre-operative cardiopulmonary exercise test. The oxygen uptake efficiency slope was calculated up to different exercise intensities, using 100%, 90% and 80% of the exercise data...
July 25, 2017: Anaesthesia
https://www.readbyqxmd.com/read/28738382/advanced-concepts-in-the-pathophysiology-of-obstructive-sleep-apnea
#8
David P White
The primary pathological event in the disorder obstructive sleep apnea (OSA) is the partial or complete closure of the pharyngeal airway during sleep in an individual with a widely patent airway during wakefulness. This yields an apnea or hypopnea with resulting hypoxia and hypercapnia, and most often requires an arousal to terminate the event. These events occur in a repetitive manner during sleep, yielding intermittent hypoxia and sleep fragmentation with their associated adverse effects on the health and quality of life of the afflicted individual...
2017: Advances in Oto-rhino-laryngology
https://www.readbyqxmd.com/read/28735925/upper-airway-flow-limitation-and-transcutaneous-carbon-dioxide-during-sleep-in-normal-pregnancy
#9
Ville Rimpilä, Riina Jernman, Katariina Lassila, Jukka Uotila, Heini Huhtala, Johanna Mäenpää, Olli Polo
OBJECTIVE: Sleep during pregnancy involves a physiological challenge to provide sufficient gas exchange to the fetus. Enhanced ventilatory responses to hypercapnia and hypoxia may protect from deficient gas exchange, but sleep-disordered breathing (SDB) may predispose to adverse events. The aim of this study was to analyze sleep and breathing in healthy pregnant women compared to non-pregnant controls, with a focus on CO2 changes and upper-airway flow limitation. METHODS: Healthy women in the third trimester and healthy non-pregnant women with normal body mass index (BMI) were recruited for polysomnography...
August 2017: Sleep Medicine
https://www.readbyqxmd.com/read/28731978/differences-in-spatiotemporal-parameters-between-trained-runners-and-untrained-participants
#10
Josué Gómez-Molina, Ana Ogueta-Alday, Christopher Stickley, Jesús Cámara, Jon Cabrejas-Ugartondo, Juan García-López
Gómez-Molina, J, Ogueta-Alday, A, Stickley, C, Tobalina, JC, Cabrejas-Ugartondo, J, and García-López, J. Differences in spatiotemporal parameters between trained runners and untrained participants. J Strength Cond Res 31(8): 2169-2175, 2017-The aim of this study was to compare the spatiotemporal parameters of trained runners and untrained participants with the same foot strike pattern (rearfoot) during running at controlled speeds. Twenty-one participants were classified in 2 groups according to their training experience: Trained (n = 10, amateur runners with long distance training experience) and Untrained (n = 11, healthy untrained participants)...
August 2017: Journal of Strength and Conditioning Research
https://www.readbyqxmd.com/read/28727673/exercise-training-improves-ventilatory-efficiency-in-patients-with-a-small-abdominal-aortic-aneurysm-a-randomized-controlled-study
#11
Ricardo M Lima, Baruch Vainshelboim, Rucha Ganatra, Ronald Dalman, Khin Chan, Jonathan Myers
PURPOSE: To investigate the effects of exercise training on ventilatory efficiency and physiological responses to submaximal exercise in subjects with small abdominal aortic aneurysm (AAA). METHODS: Sixty-five male patients (72.3 ± 7.0 years) were randomized to exercise training (n = 33) or usual care group (n = 32). Exercise subjects participated in a training groups for 3 mo. Cardiopulmonary exercise testing was performed before and after the study period and peak VO2, the ventilatory threshold (VT), the oxygen uptake efficiency slope (OUES), and the VE2/VCO2 slope were identified...
July 19, 2017: Journal of Cardiopulmonary Rehabilitation and Prevention
https://www.readbyqxmd.com/read/28713464/a-rapidly-incremented-tethered-swimming-test-for-defining-domain-specific-training-zones
#12
Dalton M Pessôa Filho, Leandro O C Siqueira, Astor R Simionato, Mário A C Espada, Daniel S Pestana, Fred J DiMenna
The purpose of this study was to investigate whether a tethered-swimming incremental test comprising small increases in resistive force applied every 60 seconds could delineate the isocapnic region during rapidly-incremented exercise. Sixteen competitive swimmers (male, n = 11; female, n = 5) performed: (a) a test to determine highest force during 30 seconds of all-out tethered swimming (Favg) and the ΔF, which represented the difference between Favg and the force required to maintain body alignment (Fbase), and (b) an incremental test beginning with 60 seconds of tethered swimming against a load that exceeded Fbase by 30% of ΔF followed by increments of 5% of ΔF every 60 seconds...
June 2017: Journal of Human Kinetics
https://www.readbyqxmd.com/read/28708126/the-effect-of-a-12-week-beta-hydroxy-beta-methylbutyrate-hmb-supplementation-on-highly-trained-combat-sports-athletes-a-randomised-double-blind-placebo-controlled-crossover-study
#13
Krzysztof Durkalec-Michalski, Jan Jeszka, Tomasz Podgórski
The aim of this study was to verify the effect of beta-hydroxy-beta-methylbutyrate (HMB) supplementation on physical capacity, body composition and the value of biochemical parameters in highly-trained combat sports athletes. Forty-two males highly-trained in combat sports were subjected to 12 weeks of supplementation with HMB and a placebo in a randomized, placebo controlled, double-blind crossover manner. Over the course of the experiment, aerobic and anaerobic capacity was determined, while analyses were conducted on body composition and levels of creatine kinase, lactate dehydrogenase, testosterone, cortisol and lactate...
July 14, 2017: Nutrients
https://www.readbyqxmd.com/read/28706467/ketogenic-diet-benefits-body-composition-and-well-being-but-not-performance-in-a-pilot-case-study-of-new-zealand-endurance-athletes
#14
Caryn Zinn, Matthew Wood, Mikki Williden, Simon Chatterton, Ed Maunder
BACKGROUND: Low-carbohydrate, high-fat and ketogenic diets are increasingly adopted by athletes for body composition and sports performance enhancements. However, as yet, there is no consensus on their efficacy in improving performance. There is also no comprehensive literature on athletes' experiences while undertaking this diet. The purpose of this pilot work was two-fold: i. to examine the effects of a non-calorie controlled ketogenic diet on body composition and performance outcomes of endurance athletes, and ii...
2017: Journal of the International Society of Sports Nutrition
https://www.readbyqxmd.com/read/28700514/low-volume-high-intensity-interval-versus-continuous-endurance-training-effects-on-hematological-and-cardiorespiratory-system-adaptations-in-professional-canoe-polo-athletes
#15
Mohsen Sheykhlouvand, Mohammadali Gharaat, Erfan Khalili, Hamid Agha-Alinejad, Farhad Rahmaninia, Hamid Arazi
The aim of this study was to compare the effect of two paddling-based high-intensity interval training (HIIT) and continuous endurance training (CET) on hematological, immunological, and cardiorespiratory adaptations in professional canoe polo athletes. Twenty one male canoe polo athletes were randomly divided into one of three groups (N=7): 1) HIIT with variable intensity (VIHIIT) (6×60-second at 100,110,120,130,130, 130,120,110,100% vV[Combining Dot Above]O2peak from 1 to 9 session respectively, 1:3 work to recovery ratio); 2) HIIT with variable volume (VVHIIT) (6,7,8,9,9,9,8,7,6 repetitions/session from 1 to 9 session respectively)×60-second at lowest velocity that elicited V[Combining Dot Above]O2peak (vV[Combining Dot Above]O2peak), 1:3 work to recovery ratio); and 3) the CET group performed 3 times × 60 min paddling sessions (75% vV[Combining Dot Above]O2peak) per week for 3 weeks...
July 8, 2017: Journal of Strength and Conditioning Research
https://www.readbyqxmd.com/read/28690872/physiological-and-lipid-profile-response-to-acute-exercise-at-different-intensities-in-individuals-with-spinal-cord-injury
#16
Eduardo S Alves, Ronaldo Vt Santos, Francieli S Ruiz, Fabio S Lira, Alexandre A Almeida, Giscard Lima, Thatiana Cs Goni, Lila Oyama, Kate M Edwards, Sergio Tufik, Marco Túlio De Mello
STUDY DESIGN: Experimental and cross-sectional study. OBJECTIVE: To assess the immediate effect of exercise on heart rate (HR), oxygen uptake (VO2), pulmonary ventilation (PV), oxygen pulse (OP), glucose and lipids of wheelchair basketball players with spinal cord injury (SCI). SETTING: Center of Studies in Psychobiology and Exercise-São Paulo, Brazil. METHODS: In all, nine wheelchair basketball players with SCI and nine able-bodied controls (C) performed three exercise sessions at different intensities: ventilatory threshold 1 (VT1), 15% below VT1 and 15% above VT1 with a duration of ~24-34 min...
2017: Spinal Cord Series and Cases
https://www.readbyqxmd.com/read/28683177/determination-of-ideal-target-exercise-heart-rate-for-cardiac-patients-suitable-for-rehabilitation
#17
Shih Jia Janice Tan, John Carson Allen, Swee Yaw Tan
BACKGROUND: Exercise prescription for patients with cardiovascular disease remains a challenge. The concept of exercising at an intensity equivalent to one's anaerobic threshold has been well studied and highly recommended in the fitness industry for other populations. For this concept to be applicable to patients with cardiovascular disease, the level and intensity of activity must not trigger myocardial ischemia. HYPOTHESIS: We hypothesized that the heart rate at ventilatory anaerobic threshold (HRVAT ) will not exceed heart rate at ischemic threshold (HRIT ) (ie, HRVAT ≤ HRIT in a majority [>50%] of patients)...
July 6, 2017: Clinical Cardiology
https://www.readbyqxmd.com/read/28674606/comparison-of-ventilatory-measures-and-20-km-time-trial-performance
#18
Willard W Peveler, Brandy Shew, Samantha Johnson, Gabe Sanders, Roger Kollock
Performance threshold measures are used to predict cycling performance. Previous research has focused on long time trials (≥ 40 km) using power at ventilatory threshold and respiratory threshold to estimate time trial performance. As intensity greatly differs during shorter time trails applying findings from longer time trials may not be appropriate. The use of heart rate measures to determine 20 km time trial performance has yet to be examined. The purpose of this study was to determine the effectiveness of heart rate measures at ventilatory threshold (VE/VO2 Plotted and VT determined by software) and respiratory threshold (RER of 0...
2017: International Journal of Exercise Science
https://www.readbyqxmd.com/read/28669689/effects-of-erythropoietin-on-cycling-performance-of-well-trained-cyclists-a-double-blind-randomised-placebo-controlled-trial
#19
Jules A A C Heuberger, Joris I Rotmans, Pim Gal, Frederik E Stuurman, Juliëtte van 't Westende, Titiaan E Post, Johannes M A Daniels, Matthijs Moerland, Peter L J van Veldhoven, Marieke L de Kam, Herman Ram, Olivier de Hon, Jelle J Posthuma, Jacobus Burggraaf, Adam F Cohen
BACKGROUND: Substances that potentially enhance performance (eg, recombinant human erythropoietin [rHuEPO]) are considered doping and are therefore forbidden in sports; however, the scientific evidence behind doping is frequently weak. We aimed to determine the effects of rHuEPO treatment in well trained cyclists on maximal, submaximal, and race performance and on safety, and to present a model clinical study for doping research on other substances. METHODS: We did this double-blind, randomised, placebo-controlled trial at the Centre for Human Drug Research in Leiden (Netherlands)...
June 29, 2017: Lancet Haematology
https://www.readbyqxmd.com/read/28657863/carbohydrate-intake-and-training-efficacy-a-randomized-cross-over-study
#20
Florian Beaudouin, Frederic Joerg, Anette Hilpert, Tim Meyer, Anne Hecksteden
Carbohydrate (CHO) availability during endurance exercise seems to attenuate exercise-induced perturbations of cellular homeostasis and might consequently diminish the stimulus for training adaptation. Therefore, a negative effect of CHO intake on endurance training efficacy seems plausible. This study aimed to test the influence of carbohydrate intake on the efficacy of an endurance training program on previously untrained healthy adults. A randomized cross-over trial (8-week wash-out period) was conducted in 23 men and women with two 8-week training periods (with vs...
June 28, 2017: Journal of Sports Sciences
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