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Integrated Cardiovascular Responses
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
The amount of oxygen consumed per volume of blood (stroke volume) delivered to the tissues is known as oxygen pulse. It is calculated as divided by heart rate and is used as a surrogate for stroke volume. It depends on the stroke volume and the arteriovenous oxygen difference. The oxygen pulse increases at the beginning of exercise before reaching a plateau at maximal oxygen consumption (its highest predicted value).
The Cardiovascular System
Published in Charles Paul Lambert, Physiology and Nutrition for Amateur Wrestling, 2020
The heart, blood vessels, and lymphatic vessels form the cardiovascular system. Cardiac Output (the amount of blood the heart pumps per minute) is an important concept for Amateur Wrestling. It is made up of the Stroke Volume, the amount of blood the heart pumps per beat, and the Heart Rate which is the number of beats per minute. Cardiac Output is a major determinant of VO2peak/max, or the amount of oxygen that can be delivered by the heart and lungs and taken up by the cells and utilized during exercise. The Arteriovenous Oxygen Difference (A-VO2 diff) is the other major determinant of VO2peak/max and is dependent on extraction of oxygen out of the blood at the tissue level. Factors which influence A-VO2 difference are capillarity, and mitochondrial size, and number.
Hemodynamic Patterns in Hypertension
Published in Giuseppe Mancia, Guido Grassi, Konstantinos P. Tsioufis, Anna F. Dominiczak, Enrico Agabiti Rosei, Manual of Hypertension of the European Society of Hypertension, 2019
Surprisingly, the SV did not increase to the same levels during exercise in patients with hypertension as in normotensive controls (1). In patients with hypertension the SI was approximately 15% lower than in normal controls during all exercise levels (50, 100 and 150 W). The increase in SI from rest to 100-Watt (W) steady-state exercise was 20.4 mL/stroke/m2 as compared with 28.4 mL/stroke/m2 in the normotensive subjects. Thus, during exercise the CI was no longer higher than in normotensive controls, but actually significantly subnormal, particularly during strenuous exercise (150 W). The oxygen consumption was similar, and as a consequence, the arteriovenous oxygen difference [(A-V)O2] was increased.
Intake Duration of Anthocyanin-Rich New Zealand Blackcurrant Extract Affects Cardiovascular Responses during Moderate-Intensity Walking But Not at Rest
Published in Journal of Dietary Supplements, 2023
Mehmet Akif Şahin, Pelin Bilgiç, Stefano Montanari, Mark Elisabeth Theodorus Willems
The present study also provided indication by lower arterio-venous oxygen difference that intake of NZBC extract can enhance tissue oxygen uptake at rest and during dynamic moderate-intensity exercise. Fryer et al. (38, 39) also provided observations of enhanced muscle oxygenation with near-infrared spectroscopy during isometric contractions of forearm skeletal muscles in climbers. It is possible that the presence of lower arterio-venous oxygen difference contributed to performance-enhancing effects in some exercise modalities by intake of NZBC extract (e.g. Ref. (40)). However, the potential benefits of lower arterio-venous oxygen difference, as observed in the present study is unclear. The lower arteriovenous oxygen difference may have been due to enhanced blood flow, compensating for enhanced cardiac output and not indicative of increased oxygen use due to our approach to calculate arteriovenous oxygen difference in the present study. However, the significant increase in cardiac output with 14-days intake of New Zealand blackcurrant without a lower value for arteriovenous oxygen difference may indicate an increase in oxygen uptake.
Fan cooling after cardiovascular drift does not reverse decrements in maximal oxygen uptake during heat stress
Published in Temperature, 2019
Jonathan E. Wingo, Jason Ng, Charles P. Katica, Stephen J. Carter
The precise mechanism(s) by which V̇O2max was reduced in the 45-min trials in the present study cannot be determined from the data collected. Maximum HR was not different between 15MIN and the 45-min trials, which suggests cardiovascular capacity had been attained and leg fatigue was improbable as a limiting factor. Likewise, maximal arteriovenous oxygen difference would not be expected to be reduced at maximum under these conditions [16]. Therefore, reduced maximal SV likely explains the reductions in V̇O2max observed. While SV likely increased during maximal exercise from levels observed during the submaximal exercise period, we suspect the peak level achieved was less than that achieved during the control and 15MIN trials. SV could have been lower at maximum because of reductions in central blood volume, central venous pressure, and end-diastolic volume in conjunction with elevated skin blood flow [45].
Elevated body temperature contributes to the increased heart rate response during eccentric compared to concentric cycling when matched for oxygen consumption
Published in Temperature, 2021
Tor Eiken, Amelia J. Harrison, Catriona A. Burdon, Herbert Groeller, Gregory E. Peoples
In this context, significantly higher muscle activation during eccentric cycling has been strongly correlated with a greater cardiac output and heart rate [12], with suggestions of potentially greater exercising muscle temperature and redirection of blood flow to the periphery for thermoregulation [12,22]. This is further supported by an observed smaller arteriovenous oxygen difference during eccentric exercise at matched oxygen consumption to concentric exercise [8,12]. In the current study, the elevation of body temperature during eccentric cycling, although clearly different from the metabolically matched concentric cycling, was confined to the upper thermal neutral zone (mean skin temperature approaching 35°C) [23]. The change in aural temperature (+0.5°C) was intentionally selected so as to minimize the duration of eccentric cycling, and therefore contractile muscle fatigue, whilst rapidly effecting a body temperature change and without meaningful dehydration (mean trial duration of 20 minutes). As such, differences in heart rate between the two trials could be more confidently assigned to thermoregulatory responses, where increased skin temperature is indicative of an increase in skin blood flow [23,24]. Furthermore, not only was the heart rate and mean skin temperature higher at trial termination, but independent of cycling condition, heart rate was significantly correlated with the elevated mean skin temperature (r2=0.43). Recent suggestion of elevated sympathetic nervous system activity, total peripheral resistance, and cardiac drift during prolonged eccentric cycling [25] also support the occurrence of an increased thermal load during eccentric cycling.