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

Surgical masks and filtering facepiece class 2 respirators (FFP2) have no major physiological effects at rest and during moderate exercise at 3000 m altitude. A randomised controlled trial

Background: During the COVID-19 pandemic, the use of face masks has been recommended or enforced in several situations, however their effects on physiological parameters and cognitive performance at high altitude are unknown. Methods: Eight healthy participants (four females) rested and exercised (cycling, 1 W/kg) while wearing no mask, a surgical mask, or a filtering facepiece class 2 respirator (FFP2), both in normoxia and hypobaric hypoxia corresponding to an altitude of 3000 m. Arterialised oxygen saturation (SaO2), partial pressure of oxygen (PaO2) and carbon dioxide (PaCO2), heart and respiratory rate, pulse oximetry (SpO2), cerebral oxygenation, visual analogue scales for dyspnoea and mask's discomfort were systematically investigated. Resting cognitive performance and exercising tympanic temperature were also assessed. Results: Mask use had a significant effect on PaCO2 (overall +1.2 ± 1.7 mmHg). There was no effect of mask use on all other investigated parameters except for dyspnoea and discomfort, which were highest with FFP2. Both masks were associated with a similar non-significant decrease in SaO2 during exercise in normoxia (-0.5% ± 0.4%) and, especially, in hypobaric hypoxia (-1.8% ± 1.5%), with similar trends for PaO2 and SpO2. Conclusions: Although mask use was associated with higher rates of dyspnoea, it had no clinically relevant impact on gas exchange at 3000 m at rest and during moderate exercise, and no detectable effect on resting cognitive performance. Wearing a surgical mask or an FFP2 can be considered safe for healthy people living, working, or spending their leisure time in mountains, high-altitude cities, or other hypobaric environments (e.g. aircrafts) up to an altitude of 3000 m

Energetics and Mechanics of human breath-hold diving

Energetics and Mechanics of human breath-hold divingEnergetics and Mechanics of human breath-hold divin

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

The physiology of submaximal exercise: The steady state concept

The steady state concept implies that the oxygen flow is invariant and equal at each level along the respiratory system. The same is the case with the carbon dioxide flow. This condition has several physiological consequences, which are analysed. First, we briefly discuss the mechanical efficiency of exercise and the energy cost of human locomotion, as well as the roles played by aerodynamic work and frictional work. Then we analyse the equations describing the oxygen flow in lungs and in blood, the effects of ventilation and of the ventilation - perfusion inequality, and the interaction between diffusion and perfusion in the lungs. The cardiovascular responses sustaining gas flow increase in blood are finally presented. An equation linking ventilation, circulation and metabolism is developed, on the hypothesis of constant oxygen flow in mixed venous blood. This equation tells that, if the pulmonary respiratory quotient stays invariant, any increase in metabolic rate is matched by a proportional increase in ventilation, but by a less than proportional increase in cardiac output

Gas exchange and cardiovascular responses during breath-holding in divers

To check whether the evolution of alveolar pressures of O2 (PAO2) and CO2 (PACO2) explains the cardiovascular responses to apnoea, eight divers performed resting apnoeas of increasing duration in air and in O2. We measured heart rate (fH), arterial pressure (AP), and peripheral resistances (TPR) beat-by-beat, PAO2 and PACO2 at the end of each apnoea. The three phases of the cardiovascular response to apnoea were observed. In O2, TPR increase (9 ± 4 mmHg min l−1) and fH decrease (-11 ± 8 bpm) were lower than in air (15 ± 5 mmHg min l−1 and -28 ± 13 bpm, respectively). At end of maximal apnoeas in air, PAO2 and PACO2 were 50 ± 9 and 48 ± 5 mmHg, respectively; corresponding values in O2 were 653 ± 8 mmHg and 55 ± 5 mmHg. At end of phase II, PAO2 and PACO2 in air were 90 ± 13 mmHg and 42 ± 4 mmHg respectively; corresponding values in O2 were 669 ± 7 mmHg and 47 ± 6 mmHg. The PACO2 increase may trigger the AP rise in phase III

Comparison of resting energy expenditure measured with metabolic cart and calculated with predictive formulas in critically ill patients on mechanical ventilation

Introduction: The purpose was to compare the resting energy expenditure (REE) measured with the Q-NRGTM+ metabolic-cart (MREE) with REE predicted by equations (the Harris-Benedict formula and an equation developed in ward, REE-HB and REE-W, respectively). We also aimed to assess the agreement of the measurements of oxygen consumption (V̇O2) and carbon dioxide production (V̇CO2) at different inspired fractions of oxygen (FiO2). Methods: 27 mechanically ventilated ICU patients were enrolled. V̇O2 and V̇CO2 were measured by Q-NRGTM+ during breathing 40% and 60% FiO2. MREE was compared with REE-W and REE-HB normalized for body weight. Results: V̇O2 was 233.0 (95.2) ml/min and 217.5 (89.8) ml/min at FiO2 40% and 60%, respectively (NS). V̇CO2 was 199.0 (91.7) ml/min at FiO2 40%, and 197.5 (85.5) ml/min at FiO2 60% (NS). The REE estimated from the equations was significantly different from the MREE. The best agreement was found for the Harris-Benedict equation without correction for stress-factors. Harris-Benedict equation corrected overestimates REE. Conclusions: This new metabolic cart Q-NRGTM+ provides a concordance of values for V̇O2 and V̇CO2 when measured at different FiO2, and is a reliable tool for estimating energy expenditure and assessing the nutritional needs of the patient. This study demonstrates that the estimation of REE using predictive formulas does not allow accurate calculation of metabolic demands in ventilated intensive care patient. However, predictive equations allow for a rapid assessment of REE and calculation of the amount of energy derived from different substrates

An effective approach to the fast, GPU-based, through-wall imaging

We present an approach for the Through-Wall-Imaging based on a simple model of the scattering problem involving few unknowns, exploiting effectively the a priori information on the scenario and using a global optimization approach, relying on Legendre-Fenchel Transforms, tailored to fast, parallel implementations on Graphic Processing Units (GPUs). Experimental results are presented against X-band data collected in a realistic scenario made of a wall of Ytong concrete blocks and a metallic cylindrical scatterer

Effects of recovery interval duration on the parameters of the critical power model for incremental exercise

INTRODUCTION: We tested the linear critical power ([Formula: see text]) model for discrete incremental ramp exercise implying recovery intervals at the end of each step. METHODS: Seven subjects performed incremental (power increment 25 W) stepwise ramps to subject's exhaustion, with recovery intervals at the end of each step. Ramps' slopes (S) were 0.83, 0.42, 0.28, 0.21, and 0.08 W s-1; recovery durations (t r) were 0 (continuous stepwise ramps), 60, and 180 s (discontinuous stepwise ramps). We determined the energy store component (W'), the peak power ([Formula: see text]), and [Formula: see text]. RESULTS: When t r = 0 s, [Formula: see text] and W' were 187 ± 26 W and 14.5 ± 5.8 kJ, respectively. When t r = 60 or 180 s, the model for ramp exercise provided inconsistent [Formula: see text] values. A more general model, implying a quadratic [Formula: see text] versus [Formula: see text] relationship, was developed. This model yielded, for t r = 60 s, [Formula: see text] = 189 ± 48 W and W' = 18.6 ± 17.8 kJ, and for t r = 180 s, [Formula: see text] = 190 ± 34 W, and W' = 16.4 ± 16.7 kJ. These [Formula: see text] and W' did not differ from the corresponding values for t r = 0 s. Nevertheless, the overall amount of energy sustaining work above [Formula: see text], due to energy store reconstitution during recovery intervals, was higher the longer t r, whence higher [Formula: see text] values. CONCLUSIONS: The linear [Formula: see text] model for ramp exercise represents a particular case (for t r = 0 s) of a more general model, accounting for energy resynthesis following oxygen deficit payment during recovery

Alveolar gas composition during maximal and interrupted apnoeas in ambient air and pure oxygen

INTRODUCTION: We tested the hypothesis that the alveolar gas composition at the transition between the steady phase II (\u3c62) and the dynamic phase III (\u3c63) of the cardiovascular response to apnoea may lay on the physiological breaking point curve (Lin et al., 1974). METHODS: Twelve elite divers performed maximal and \u3c62-interrupted apnoeas, in air and pure oxygen. We recorded beat-by-beat arterial blood pressure and heart rate; we measured alveolar oxygen and carbon dioxide pressures (PAO2 and PACO2, respectively) before and after apnoeas; we calculated the PACO2 difference between the end and the beginning of apnoeas (\u394PACO2). RESULTS: Cardiovascular responses to apnoea were similar compared to previous studies. PAO2 and PACO2 at the end of \u3c62-interrupted apnoeas, corresponded to those reported at the physiological breaking point. For maximal apnoeas, PACO2 was less than reported by Lin et al. (1974). \u394PACO2 was higher in oxygen than in air. CONCLUSIONS: The transition between \u3c62 and \u3c63 corresponds indeed to the physiological breaking point. We attribute this transition to \u394PACO2, rather than the absolute PACO2 values, both in air and oxygen apnoeas