Modeling the Power-Duration Relationship in Professional Cyclists During the Giro d'Italia

Vinetti, G, Pollastri, L, Lanfranconi, F, Bruseghini, P, Taboni, A, and Ferretti, G. Modeling the power-duration relationship in professional cyclists during the Giro d'Italia. J Strength Cond Res XX(X): 000-000, 2022-Multistage road bicycle races allow the assessment of maximal mean power output (MMP) over a wide spectrum of durations. By modeling the resulting power-duration relationship, the critical power (CP) and the curvature constant (W') can be calculated and, in the 3-parameter (3-p) model, also the maximal instantaneous power (P0). Our aim is to test the 3-p model for the first time in this context and to compare it with the 2-parameter (2-p) model. A team of 9 male professional cyclists participated in the 2014 Giro d'Italia with a crank-based power meter. The maximal mean power output between 10 seconds and 10 minutes were fitted with 3-p, whereas those between 1 and 10 minutes with the 2- model. The level of significance was set at p < 0.05. 3-p yielded CP 357 ± 29 W, W' 13.3 ± 4.2 kJ, and P0 1,330 ± 251 W with a SEE of 10 ± 5 W, 3.0 ± 1.7 kJ, and 507 ± 528 W, respectively. 2-p yielded a CP and W' slightly higher (+4 ± 2 W) and lower (-2.3 ± 1.1 kJ), respectively (p < 0.001 for both). Model predictions were within ±10 W of the 20-minute MMP of time-trial stages. In conclusion, during a single multistage racing event, the 3-p model accurately described the power-duration relationship over a wider MMP range without physiologically relevant differences in CP with respect to 2-p, potentially offering a noninvasive tool to evaluate competitive cyclists at the peak of training

Vagal blockade suppresses the phase I heart rate response but not the phase I cardiac output response at exercise onset in humans

Purpose We tested the vagal withdrawal concept for heart rate (HR) and cardiac output (CO) kinetics upon moderate exercise onset, by analysing the effects of vagal blockade on cardiovascular kinetics in humans. We hypothesized that, under atropine, the φ1 amplitude (A1) for HR would reduce to nil, whereas the A1 for CO would still be positive, due to the sudden increase in stroke volume (SV) at exercise onset. Methods On nine young non-smoking men, during 0–80 W exercise transients of 5-min duration on the cycle ergometer, preceded by 5-min rest, we continuously recorded HR, CO, SV and oxygen uptake (˙O2) upright and supine, in control condition and after full vagal blockade with atropine. Kinetics were analysed with the double exponential model, wherein we computed the amplitudes (A) and time constants (τ) of phase 1 (φ1) and phase 2 (φ2). Results In atropine versus control, A1 for HR was strongly reduced and fell to 0 bpm in seven out of nine subjects for HR was practically suppressed by atropine in them. The A1 for CO was lower in atropine, but not reduced to nil. Thus, SV only determined A1 for CO in atropine. A2 did not differ between control and atropine. No effect on τ1 and τ2 was found. These patterns were independent of posture. Conclusion The results are fully compatible with the tested hypothesis. They provide the first direct demonstration that vagal blockade, while suppressing HR φ1, did not affect φ1 of CO

The RES approach for debris flow susceptibility analysis: A case study

Climate change has increased the occurrence and magnitude of debris flow events, especially in mountain areas. Moreover, their unpredictability requires to develop reliable methodologies for the evaluation of debris flow susceptibility, which is the starting point for risk assessment and management. In this paper, a modified version of the Debris flow Propensity Index (DfPI) is developed for the debris flow susceptibility estimation at basin scale. Bedrock lithology, fracture network, quaternary deposits, slope angle, channel network, and land use were identified as debris flow predisposing factors and were indexed by using open-access data and geodatabases. The objective of the proposed study is to develop a simple and economic procedure for the susceptibility estimation, easily to implement in GIS-based software for further analyses, such as propagation simulations or hazard scenarios, useful for planning mitigation strategies. The Can? Valley, a small valley located in the more famous Camonica Valley, (Lombardia Region, Northern Italy), was used as a case study for developing and testing the proposed approach

Arterial baroreflexes in dynamic conditions in humans

The arterial baroreflex is an important blood pressure short-term control system. Its response characteristics are modulated under several conditions. Previous literature analysing the baroreflex under strict steady state conditions postulated that a central feed-forward command and some peripheral reflexes are responsible for the baroreflex modulation. A seminal work that analysed the baroreflex dynamics during a rest-to-exercise transient hypothesised that the central command may act through vagal withdrawal. The aim of the current work was to test this hypothesis by analysing the dynamic response of the baroreflex characteristics during unsteady state conditions characterised by different vagal activity. Four experiments investigated the light-to-moderate exercise transient, the rest-to-exercise transient in hypoxia, the abrupt postural change, and the fast cardiovascular response to breath holding at high lung volumes. The baroreflex was analysed through the linear relationship between the pulse interval and the mean arterial pressure. The results were in line with the tested hypothesis

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

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