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The Canadian Journal of Cardiology Dec 2014In this article, new areas of cardiovascular (CV) prevention and rehabilitation research are discussed: high-intensity interval training (HIIT) and new concepts in... (Review)
Review
In this article, new areas of cardiovascular (CV) prevention and rehabilitation research are discussed: high-intensity interval training (HIIT) and new concepts in nutrition. HIIT consists of brief periods of high-intensity exercise interspersed by periods of low-intensity exercise or rest. The optimal mode according our work (15-second exercise intervals at peak power with passive recovery intervals of the same duration) is associated with longer total exercise time, similar time spent near peak oxygen uptake (VO2 peak) VO2 peak, and lesser perceived exertion relative to other protocols that use longer intervals and active recovery periods. Evidence also suggests that compared with moderate-intensity continuous exercise training, HIIT has superior effects on cardiorespiratory function and on the attenuation of multiple cardiac and peripheral abnormalities. With respect to nutrition, a growing body of evidence suggests that the gut microbiota is influenced by lifestyle choices and might play a pivotal role in modulating CV disease development. For example, recent evidence linking processed (but not unprocessed) meats to increased CV risk pointed to the gut microbial metabolite trimethylamine N-oxide as a potential culprit. In addition, altered gut microbiota could also mediate the proinflammatory and cardiometabolic abnormalities associated with excess added free sugar consumption, and in particular high-fructose corn syrup. Substantially more research is required, however, to fully understand how and which alterations in gut flora can prevent or lead to CV disease and other chronic illnesses. We conclude with thoughts about the appropriate role for HIIT in CV training and future research in the role of gut flora-directed interventions in CV prevention.
Topics: Exercise; Heart Diseases; Humans; Life Style; Oxygen Consumption
PubMed: 25444498
DOI: 10.1016/j.cjca.2014.09.014 -
Experimental Eye Research Oct 2018Light flicker stimulation has been shown to increase inner retinal oxygen metabolism and supply. The purpose of the study was to test the hypothesis that sustained light...
Light flicker stimulation has been shown to increase inner retinal oxygen metabolism and supply. The purpose of the study was to test the hypothesis that sustained light flicker stimulation of various durations alters the depth profile metrics of oxygen partial pressure in the retinal tissue (tPO) but not the outer retinal oxygen consumption rate (QO). In 17 rats, tPO depth profiles were derived by phosphorescence lifetime imaging after intravitreal injection of an oxyphor. tPO profile metrics, including mean inner retinal tPO, maximum outer retinal tPO and minimum outer retinal tPO were determined. QO was calculated using a one-dimensional oxygen diffusion model. Data were acquired at baseline (constant light illumination) and during light flicker stimulation at 10 Hz under the same mean illumination levels, and differences between values obtained during flicker and baseline were calculated. None of the tPO profile metrics or QO differences depended on the duration of light flicker stimulation (R ≤ 0.03). No significant change in any of the tPO profile metrics was detected with light flicker compared with constant light (P ≥ 0.08). Light flicker decreased QO from 0.53 ± 0.29 to 0.38 ± 0.30 mL O/(min*100 gm), a reduction of 28% (P = 0.02). The retinal compensatory responses to the physiologic challenge of light flicker stimulation were effective in maintaining the levels of oxygen at or near baseline in the inner retina. Oxygen availability to the inner retina during light flicker may also have been enhanced by the decrease in QO.
Topics: Animals; Light; Male; Oxygen; Oxygen Consumption; Photic Stimulation; Rats; Rats, Long-Evans; Retina
PubMed: 30121195
DOI: 10.1016/j.exer.2018.08.007 -
Experimental Physiology Dec 2020
Topics: Exercise; Exercise Test; Humans; Oxygen; Oxygen Consumption; Respiratory Muscles
PubMed: 33372725
DOI: 10.1113/EP089199 -
International Journal of Environmental... Sep 2022Uphill running induces a higher physiological demand than level conditions. Although many studies have investigated this locomotion from a psychological point of view,...
Uphill running induces a higher physiological demand than level conditions. Although many studies have investigated this locomotion from a psychological point of view, there is no clear position on the effects of the slope on the physiological variables during an incremental running test performed on a slope condition. The existing studies have heterogeneous designs with different populations or slopes and have reported unclear results. Some studies observed an increase in oxygen consumption, whereas it remained unaffected in others. The aim of this study is to investigate the effect of a slope on the oxygen consumption, breathing frequency, ventilation and heart rate during an incremental test performed on 0, 15, 25 and 40% gradient slopes by specialist trail runners. The values are compared at the first and second ventilatory threshold and exhaustion. A one-way repeated measures ANOVA, with a Bonferroni post-hoc analysis, was used to determine the effects of a slope gradient (0, 15, 25 and 40%) on the physiological variables. Our study shows that all the variables are not affected in same way by the slopes during the incremental test. The heart rate and breathing frequency did not differ from the level condition and all the slope gradients at the ventilatory thresholds or exhaustion. At the same time, the ventilation and oxygen consumption increased concomitantly with the slope ( < 0.001) in all positions. The post-hoc analysis highlighted that the ventilation significantly increased between each successive gradient (0 to 15%, 15% to 25% and 25% to 40%), while the oxygen consumption stopped increasing at the 25% gradient. Our results show that the 25 and 40% gradient slopes allow the specialist trail runners to reach the highest oxygen consumption level.
Topics: Exercise Test; Heart Rate; Oxygen Consumption; Respiration; Running
PubMed: 36231513
DOI: 10.3390/ijerph191912210 -
BMC Anesthesiology Jun 2023Body temperature (BT) is thought to have associations with oxygen consumption (VO). However, there have been few studies in which the association between systemic VO and...
BACKGROUND
Body temperature (BT) is thought to have associations with oxygen consumption (VO). However, there have been few studies in which the association between systemic VO and BT in humans was investigated in a wide range of BTs. The aims of this study were 1) to determine the association between VO and age and 2) to determine the association between VO and BT.
METHODS
This study was a retrospective study of patients who underwent surgery under general anesthesia at a tertiary teaching hospital. VO was measured by the Dräger Perseus A500 anesthesia workstation (Dräger Medical, Lubeck, Germany). The associations of VO with age and BT were examined using spline regression and multivariable regression analysis with a random effect.
RESULTS
A total of 7,567 cases were included in this study. A linear spline with one knot shows that VO was reduced by 2.1 ml/kg/min with one year of age (p < 0.001) among patients less than 18 years of age and that there was no significant change in VO among patients 18 years of age or older (estimate: 0.014 ml/kg/min, p = 0.08). VO in all bands of BT < 36.0 °C was not significantly different from VO in BT > = 36 °C and < 36.5 °C. Multivariable linear regression analysis showed that compared with VO in BT > = 36 °C and < 36.5 °C as a reference, VO levels were significantly higher by 0.57 ml/kg/min in BT > = 36.5 °C and < 37 °C (p < 0.001), by 1.8 ml/kg/min in BT > = 37 °C and < 37.5 °C (p < 0.001), by 3.6 ml/kg/min in BT > = 37.5 °C and < 38 °C (p < 0.001), by 4.9 ml/kg/min in BT > = 38 °C and < 38.5 °C (p < 0.001), and by 5.7 ml/kg/min in BT > = 38.5 °C (p < 0.001). The associations between VO and BT were significantly different among categorized age groups (p = 0.03).
CONCLUSIONS
VO increases in parallel with increase in body temperature in a hyperthermic state but remains constant in a hypothermic state. Neonates and infants, who have high VO, may have a large systemic organ response in VO to change in BT.
Topics: Infant; Infant, Newborn; Humans; Adolescent; Adult; Child, Preschool; Body Temperature; Retrospective Studies; Anesthesia, General; Fever; Oxygen Consumption; Oxygen
PubMed: 37340340
DOI: 10.1186/s12871-023-02182-1 -
International Journal of Sports... Nov 2021Since its publication in 2012, the W' balance model has become an important tool in the scientific armamentarium for understanding and predicting human physiology and... (Review)
Review
Since its publication in 2012, the W' balance model has become an important tool in the scientific armamentarium for understanding and predicting human physiology and performance during high-intensity intermittent exercise. Indeed, publications featuring the model are accumulating, and it has been adapted for popular use both in desktop computer software and on wrist-worn devices. Despite the model's intuitive appeal, it has achieved mixed results thus far, in part due to a lack of clarity in its basis and calculation. Purpose: This review examines the theoretical basis, assumptions, calculation methods, and the strengths and limitations of the integral and differential forms of the W' balance model. In particular, the authors emphasize that the formulations are based on distinct assumptions about the depletion and reconstitution of W' during intermittent exercise; understanding the distinctions between the 2 forms will enable practitioners to correctly implement the models and interpret their results. The authors then discuss foundational issues affecting the validity and utility of the model, followed by evaluating potential modifications and suggesting avenues for further research. Conclusions: The W' balance model has served as a valuable conceptual and computational tool. Improved versions may better predict performance and further advance the physiology of high-intensity intermittent exercise.
Topics: Exercise; Exercise Test; High-Intensity Interval Training; Humans; Oxygen Consumption
PubMed: 34686611
DOI: 10.1123/ijspp.2021-0205 -
Cardiology Clinics Feb 2023The noninvasive assessment of oxygen consumption, carbon dioxide production, and ventilation during a cardiopulmonary exercise test (CPET) provides insight into the... (Review)
Review
The noninvasive assessment of oxygen consumption, carbon dioxide production, and ventilation during a cardiopulmonary exercise test (CPET) provides insight into the cardiovascular, pulmonary, and metabolic system's ability to respond to exercise. Exercise physiology has been shown to be distinct for competitive athletes and highly active persons (CAHAPs), thus creating more nuanced interpretations of CPET parameters. CPET in CAHAP is an important test that can be used for both diagnosis (provoking symptoms during a truly maximal test) and performance.
Topics: Humans; Exercise Test; Cardiologists; Oxygen Consumption; Exercise Tolerance; Athletes
PubMed: 36368812
DOI: 10.1016/j.ccl.2022.08.006 -
Journal of the International Society of... Dec 2023Rectal distension increases regulatory burden to autonomic nervous system in the brain.
BACKGROUND
Rectal distension increases regulatory burden to autonomic nervous system in the brain.
PURPOSE
To determine the effect of rectal defecation on endurance performance and blood supply to the prefrontal brain and sub-navel regions of elite triathletes.
METHODS
Thirteen elite triathletes completed a cycling time trial (80% VO) under defecated and non-defecated conditions, using a counterbalanced crossover design. Oxygenation and blood distribution in prefrontal brain and sub-navel regions were monitored by near-infrared spectroscopy (NIRS) during cycling.
RESULTS
Defecation moderately decreased systolic blood pressure (-4 mmHg, < 0.05, d = 0.71), suggesting an alleviation of autonomic nervous activity. During the exercise trials, fatigue (cycling time to exhaustion) occurred when cerebral oxygenation decreased to ~ 5 % below baseline regardless of treatment conditions, suggesting a critical deoxygenation point for sustaining voluntary exertions. Cerebral blood (estimated by total hemoglobin) increased progressively throughout the entire exercise period. Defecation decreased sub-navel oxygenation levels below the non-defecated level, suggesting an increased sub-navel oxygen consumption. Exercise also decreased sub-navel blood distribution, with minimal difference between non-defecated and defecated conditions. Defecation improved blood pooling in the prefrontal brain during exercise ( < 0.05) and enhanced cycling performance in triathletes (Non-defecated: 1624 ± 138 s vs. defecated: 1902 ± 163 s, d = 0.51, < 0.05).
CONCLUSION
Our results suggest that improved exercise performance after defecation is associated with greater blood availability to compensate deoxygenation in the prefrontal brain region during exercise. Further investigation is needed to examine the role of increasing sub-navel oxygen consumption in the performance improvement after defecation.
Topics: Humans; Defecation; Exercise; Oxygen Consumption; Fatigue; Cerebrovascular Circulation
PubMed: 37102434
DOI: 10.1080/15502783.2023.2206380 -
Journal of Sport Rehabilitation Aug 2022Previous work has demonstrated an improvement in running economy during sustained running on a lower body positive pressure treadmill, but neuromuscular and...
CONTEXT
Previous work has demonstrated an improvement in running economy during sustained running on a lower body positive pressure treadmill, but neuromuscular and spatiotemporal measures have only been investigated during short-duration running bouts on these devices. The current study sought to replicate the noted metabolic response and investigate whether neuromuscular and/or spatiotemporal adaptations underlie the noted improvements in running economy.
DESIGN
Cross-sectional.
METHODS
Fifteen trained runners (11 males and 4 females) ran three 15-minute trials with 30% bodyweight support at 70% of the speed that elicited their peak oxygen consumption while running on a standard treadmill. A series of 1-way analyses of variance with repeated measures were used to explore differences in dependent variables over the 45 minutes of running. Dependent variables included oxygen consumption, root-mean-square electromyography of the vastus medialis and medial gastrocnemius during stance, and spatiotemporal parameters.
RESULTS
Oxygen consumption decreased after the initial exposure, with no further reductions after 20 minutes. Root-mean-square electromyography of the vastus medialis and medial gastrocnemius also decreased over time, with no further reductions after 20 and 10 minutes, respectively. No differences in spatiotemporal parameters were found.
CONCLUSIONS
Future research should provide sufficient time for runners to develop a more economical gait pattern prior to collecting dependent variables, and previous findings using lower body positive pressure treadmills may need to be reconsidered. Athletes using these devices for training or rehabilitation should note that increased economy will lower the intensity of a given treadmill setting over time.
Topics: Biomechanical Phenomena; Body Weight; Cross-Sectional Studies; Electromyography; Exercise Test; Female; Humans; Male; Oxygen Consumption; Running
PubMed: 35453119
DOI: 10.1123/jsr.2021-0379 -
Methods in Molecular Biology (Clifton,... 2024An analysis of the mitochondrial respiration function represented by the oxygen consumption rate is necessary to assess mitochondrial bioenergetics and redox function....
An analysis of the mitochondrial respiration function represented by the oxygen consumption rate is necessary to assess mitochondrial bioenergetics and redox function. This protocol describes two alternative techniques to evaluate mitochondrial respiration function in situ: (1) measure oxygen consumption rates via an electrode; (2) measure oxygen consumption rates via a seahorse instrument. These in situ approaches provide more physiological access to mitochondria to evaluate mitochondrial respiration function in a relatively integrated cellular system.
Topics: Oxygen Consumption; Respiration; Mitochondria; Electrodes; Respiratory Function Tests
PubMed: 38319581
DOI: 10.1007/978-1-0716-3633-6_16