The physiology of submaximal exercise: The steady state concept

Ferretti, Guido; Fagoni, Nazzareno; Taboni, Anna; Bruseghini, Paolo; Vinetti, Giovanni

doi:10.1016/j.resp.2017.08.005

Cited by 36 publications

(26 citation statements)

References 76 publications

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“…A cycle-ergometer (Ergoselect 400, Ergoline GmbH, Bitz, Germany) was mounted on the table, then in supine position the subject started to pedal at 30 W, 60 rpm, and kept exercising until the end of the procedure. Parameters recording started after attainment of the exercise steady state (Ferretti et al 2017). Then, after further 300 s, to obtain PRE-ss values, the subjects performed a series of five sub-maximal apnoeas of at least 30 s plus one maximal apnoea.…”

Section: Methodsmentioning

confidence: 99%

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

et al. 2020

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Purpose We analysed the characteristics of arterial baroreflexes during the first phase of apnoea (φ1). Methods 12 divers performed rest and exercise (30 W) apnoeas (air and oxygen). We measured beat-by-beat R-to-R interval (RRi) and mean arterial pressure (MAP). Mean RRi and MAP values defined the operating point (OP) before (PRE-ss) and in the second phase (φ2) of apnoea. Baroreflex sensitivity (BRS, ms·mmHg−1) was calculated with the sequence method. Results In PRE-ss, BRS was (median [IQR]): at rest, 20.3 [10.0–28.6] in air and 18.8 [13.8–25.2] in O2; at exercise 9.2[8.4–13.2] in air and 10.1[8.4–13.6] in O2. In φ1, during MAP decrease, BRS was lower than in PRE-ss at rest (6.6 [5.3–11.4] in air and 7.7 [4.9–14.3] in O2, p < 0.05). At exercise, BRS in φ1 was 6.4 [3.9–13.1] in air and 6.7 [4.1–9.5] in O2. After attainment of minimum MAP (MAPmin), baroreflex resetting started. After attainment of minimum RRi, baroreflex sequences reappeared. In φ2, BRS at rest was 12.1 [9.6–16.2] in air, 12.9 [9.2–15.8] in O2. At exercise (no φ2 in air), it was 7.9 [5.4–10.7] in O2. In φ2, OP acts at higher MAP values. Conclusion In apnoea φ1, there is a sudden correction of MAP fall via baroreflex. The lower BRS in the earliest φ1 suggests a possible parasympathetic mechanism underpinning this reduction. After MAPmin, baroreflex resets, displacing its OP at higher MAP level; thus, resetting may not be due to central command. After resetting, restoration of BRS suggests re-establishment of vagal drive.

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Section: Methodsmentioning

confidence: 99%

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

et al. 2020

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“…From a mechanical perspective, the authors believe that the elastic mechanism was even more optimized, because the heavier weight provided by load addition would improve the storage of elastic energy (Cavagna, 2009), thereby raising eff further (Cavagna and Legramandi, 2015). Conversely, the increased value of C metab with heavier loads can be explained by a more pronounced increase of the ventilatory response verified in steady-state conditions (Ferretti et al, 2017). Thus, both running in slope and running carrying load did not change the relation between economy and eff observed in the level condition.…”

Section: Efficiency Economy and Power Relationshipmentioning

confidence: 99%

Locomotion as a Powerful Model to Study Integrative Physiology: Efficiency, Economy, and Power Relationship

Peyré‐Tartaruga

Coertjens

2018

Front. Physiol.

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Locomotion is the most common form of movement in nature. Its study allows analysis of interactions between muscle functions (motor) and lever system arrangements (transmission), thereby facilitating performance analysis of various body organs and systems. Thus, it is a powerful model to study various aspects of integrative physiology. The results of this model can be applied in understanding body functions and design principles as performance outputs of interest for medical and biological sciences. The overall efficiency (effoverall) during locomotion is an example of an integrative parameter, which results from the ratio between mechanical output and metabolic input. Although the concepts of cost (i.e., metabolic expenditure relative to distance) and power (i.e., metabolic expenditure relative to time) are included in its calculation, the effoverall establishes peculiar relations with these variables. For a better approach to these aspects, in this study, we presented the physical-mathematical formulation of efficiency, as well as its conceptual definitions and applications. Furthermore, the concepts of efficiency, cost, and power are discussed from the biological and medical perspectives. Terrestrial locomotion is a powerful model to study integrative physiology in humans, because by analyzing the mechanical and metabolic determinants, we may verify the efficiency and economy relationship through locomotion type, and its characteristics and restrictions. Thus, it is possible to elaborate further on various improved intervention strategies, such as physical training, competition strategies, and ergogenic supplementation.

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“…Steady state data for each variable were then obtained as the mean of the beat-by-beat values at rest, between 70 and 10 s before exercise start, and during the 5 th min of exercise. The arterial-venous oxygen concentration difference (Ca O 2 -C v ̅ O 2 ) was calculated at rest and during exercise steady state, as the ratio between steady state V O 2 and CO, as discussed elsewhere [36,37].…”

Section: Data Treatmentmentioning

confidence: 99%

Effect of Lower Body Negative Pressure on Phase I Cardiovascular Responses at Exercise Onset

et al. 2020

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We hypothesised that vagal withdrawal and increased venous return interact in determining the rapid cardiac output (CO) response (phase I) at exercise onset. We used lower body negative pressure (LBNP) to increase blood distribution to the heart by muscle pump action and reduce resting vagal activity. We expected a larger increase in stroke volume (SV) and smaller for heart rate (HR) at progressively stronger LBNP levels, therefore CO response would remain unchanged. To this aim ten young, healthy males performed a 50 W exercise in supine position at 0 (Control), −15, −30 and −45 mmHg LBNP exposure. On single beat basis, we measured HR, SV, and CO. Oxygen uptake was measured breath-by-breath. Phase I response amplitudes were obtained applying an exponential model. LBNP increased SV response amplitude threefold from Control to −45 mmHg. HR response amplitude tended to decrease and prevented changes in CO response. The rapid response of CO explained that of oxygen uptake. The rapid SV kinetics at exercise onset is compatible with an increased venous return, whereas the vagal withdrawal conjecture cannot be dismissed for HR. The rapid CO response may indeed be the result of two independent yet parallel mechanisms, one acting on SV, the other on HR.

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The physiology of submaximal exercise: The steady state concept

Cited by 36 publications

References 76 publications

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

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

Locomotion as a Powerful Model to Study Integrative Physiology: Efficiency, Economy, and Power Relationship

Effect of Lower Body Negative Pressure on Phase I Cardiovascular Responses at Exercise Onset

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