Baroreflex responses during dry resting and exercise apnoeas in air and pure oxygen

Taboni, Anna; Vinetti, Giovanni; Fontolliet, Timothée; Grasso, Gabriele; Tam, Enrico; Moia, Christian; Ferretti, Guido; Fagoni, Nazzareno

doi:10.1007/s00421-020-04544-w

Cited by 7 publications

(3 citation statements)

References 38 publications

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“…Notwithstanding, we cannot dismiss central command as a potential mechanism behind the reduction of baroreflex gain at exercise onset, in view of its immediacy. Similar conclusions were more recently attained by applying the same approach to the analysis of baroreflex changes during breath-holding (Taboni et al 2021a ) and during tilting (Taboni et al 2021b ).…”

Section: On Short-term Pressure Regulationsupporting

confidence: 81%

A century of exercise physiology: key concepts on coupling respiratory oxygen flow to muscle energy demand during exercise

et al. 2022

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After a short historical account, and a discussion of Hill and Meyerhof’s theory of the energetics of muscular exercise, we analyse steady-state rest and exercise as the condition wherein coupling of respiration to metabolism is most perfect. The quantitative relationships show that the homeostatic equilibrium, centred around arterial pH of 7.4 and arterial carbon dioxide partial pressure of 40 mmHg, is attained when the ratio of alveolar ventilation to carbon dioxide flow ($${\dot{V}}_{A}/{\dot{V}}_{R}{CO}_{2}$$ V ˙ A / V ˙ R CO 2 ) is − 21.6. Several combinations, exploited during exercise, of pertinent respiratory variables are compatible with this equilibrium, allowing adjustment of oxygen flow to oxygen demand without its alteration. During exercise transients, the balance is broken, but the coupling of respiration to metabolism is preserved when, as during moderate exercise, the respiratory system responds faster than the metabolic pathways. At higher exercise intensities, early blood lactate accumulation suggests that the coupling of respiration to metabolism is transiently broken, to be re-established when, at steady state, blood lactate stabilizes at higher levels than resting. In the severe exercise domain, coupling cannot be re-established, so that anaerobic lactic metabolism also contributes to sustain energy demand, lactate concentration goes up and arterial pH falls continuously. The $${\dot{V}}_{A}/{\dot{V}}_{R}{CO}_{2}$$ V ˙ A / V ˙ R CO 2 decreases below − 21.6, because of ensuing hyperventilation, while lactate keeps being accumulated, so that exercise is rapidly interrupted. The most extreme rupture of the homeostatic equilibrium occurs during breath-holding, because oxygen flow from ambient air to mitochondria is interrupted. No coupling at all is possible between respiration and metabolism in this case.

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Section: On Short-term Pressure Regulationsupporting

confidence: 81%

A century of exercise physiology: key concepts on coupling respiratory oxygen flow to muscle energy demand during exercise

et al. 2022

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“…Hence, if we would like to investigate the dynamics of baroreflex readjustments upon exercise start, we are obliged to use a closed-loop approach. Previous literature showed that a modified sequence method can be utilised to this aim (Bringard et al 2017;Taboni et al 2021b, a).…”

Section: Methodological Considerationmentioning

confidence: 99%

Dynamics of cardiovascular and baroreflex readjustments during a light-to-moderate exercise transient in humans

et al. 2022

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Purpose We hypothesised that, during a light-to-moderate exercise transient, compared to an equivalent rest-to-exercise transient, (1) a further baroreflex sensitivity (BRS) decrease would be slower, (2) no rapid heart rate (HR) response would occur, and (3) the rapid cardiac output (CO) response would have a smaller amplitude (A1). Hence, we analysed the dynamics of arterial baroreflexes and the HR and CO kinetics during rest-to-50 W (0–50 W) and 50-to-100 W (50–100 W) exercise transients. Methods 10 subjects performed three 0–50 W and three 50–100 W on a cycle ergometer. We recorded arterial blood pressure profiles (photo-plethysmography) and R-to-R interval (RRi, electrocardiography). The former were analysed to obtain beat-by-beat mean arterial pressure (MAP) and stroke volume (SV). CO was calculated as SV times HR. BRS was measured by modified sequence method. Results During 0–50 W, MAP transiently fell (− 9.0 ± 5.7 mmHg, p < 0.01) and BRS passed from 15.0 ± 3.7 at rest to 7.3 ± 2.4 ms mmHg−1 at 50 W (p < 0.01) promptly (first BRS sequence: 8.1 ± 4.6 ms mmHg−1, p < 0.01 vs. rest). During 50–100 W, MAP did not fall and BRS passed from 7.2 ± 2.6 at 50 W to 3.3 ± 1.3 ms mmHg−1 at 100 W (p < 0.01) slowly (first BRS sequence: 5.3 ± 3.1 ms mmHg−1, p = 0.07 vs. 50 W). A1 for HR was 9.2 ± 6.0 and 6.0 ± 4.5 min−1 in 0–50 W and 50–100 W, respectively (p = 0.19). The corresponding A1 for CO were 2.80 ± 1.54 and 0.91 ± 0.55 l∙min−1 (p < 0.01). Conclusion During 50–100 W, with respect to 0–50 W, BRS decreased more slowly, in absence of a prompt pressure decrease. BRS decrease and rapid HR response in 50–100 W were unexpected and ascribed to possible persistence of some vagal tone at 50 W.

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“…A practical application of this study is evident. The need to quantify the equivalent mechanical power of cycling in water with respect to air could be crucial in several circumstances: the validation and testing of equipment for self-contained underwater breathing apparatus (29,30) and breath-hold diving (31,32), the comparison of the physiological responses between dry and wet exercise, either eupneic (13,33,34) or apneic (35)(36)(37), the proper prescription of water-based rehabilitation (33,38,39). In such cases, it could be of help to plot our overall difference in Ė between WET and DRY against f p 3 (Fig.…”

Section: Applied Sciencesmentioning

confidence: 99%

Effects of Water Immersion on the Internal Power of Cycling

Vinetti

Ferretti

Hostler

2021

Medicine &Amp; Science in Sports &Amp; Exercise

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Purpose Water immersion adds additional drag and metabolic demand for limb movement with respect to air, but its effect on the internal metabolic power ( Ė int ) of cycling is unknown. We aimed at quantifying the increase in Ė int during underwater cycling with respect to dry conditions at different pedaling rates. Methods Twelve healthy subjects (four women) pedaled on a waterproof cycle ergometer in an experimental pool that was either empty (DRY) or filled with tap water at 30.8°C ± 0.6°C (WET). Four different pedal cadences ( f p ) were studied (40, 50, 60, and 70 rpm) at 25, 50, 75, and 100 W. The metabolic power at steady state was measured via open circuit respirometry, and Ė int was calculated as the metabolic power extrapolated for 0 W. Results The Ė int was significantly higher in WET than in DRY at 50, 60, and 70 rpm (81 ± 31 vs 32 ± 30 W, 167 ± 35 vs 50 ± 29 W, 311 ± 51 vs 81 ± 30 W, respectively, all P < 0.0001), but not at 40 rpm (16 ± 5 vs 11 ± 17 W, P > 0.99). Ė int increased with the third power of f p both in WET and DRY ( R 2 = 0.49 and 0.91, respectively). Conclusions Water drag increased Ė int , although limbs unloading via the Archimedes’ principle and limbs shape could be potential confounding factors. A simple formula was developed to predict the increase in mechanical power in dry conditions needed to match the rate of energy expenditure during underwater cycling: 44 f p 3 – 7 W, where f p is expressed in Hertz.

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Baroreflex responses during dry resting and exercise apnoeas in air and pure oxygen

Cited by 7 publications

References 38 publications

A century of exercise physiology: key concepts on coupling respiratory oxygen flow to muscle energy demand during exercise

A century of exercise physiology: key concepts on coupling respiratory oxygen flow to muscle energy demand during exercise

Dynamics of cardiovascular and baroreflex readjustments during a light-to-moderate exercise transient in humans

Effects of Water Immersion on the Internal Power of Cycling

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