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Aims: To characterize the oxygenation responses at cerebral and locomotor muscle level to incremental exercise in children and to assess the interrelationship with the pulmonary gas exchange responses., Methods: Eighteen children (9 boys, 9 girls) (mean age 10.9 ± 1.0 years) performed incremental cycle ramp exercise to exhaustion. The concentration of cerebral and muscle oxygenated (O 2 Hb) and deoxygenated (HHb) hemoglobin (by means of near-infrared spectroscopy) and pulmonary gas exchange was recorded. Cerebral and muscle O 2 Hb and HHb values were expressed as functions of oxygen uptake (VO 2 ) and breakpoints were detected by means of double linear model analysis. The respiratory compensation point (RCP) was determined. The breakpoints in cerebral and muscle O 2 Hb and HHb were compared and correlated to RCP., Results: The subjects reached peak power output of 105 ± 18 W and VO 2peak of 43.5 ± 7.0 ml min -1  kg -1 . Cerebral O 2 Hb increased to an intensity of 89.4 ± 5.5 %VO 2peak , where a breakpoint occurred at which cerebral O 2 Hb started to decrease. Cerebral HHb increased slightly to 88.1 ± 4.8 %VO 2peak , at which the increase was accelerated. Muscle HHb increased to 90.5 ± 4.8 %VO 2peak where a leveling-off occurred. RCP occurred at 89.3 ± 4.3 %VO 2peak . The breakpoints and RCP did not differ significantly (P = 0.13) and were strongly correlated (r > 0.70, P < 0.05). There were no differences between boys and girls (P = 0.43) and there was no significant correlation with VO 2peak (P > 0.05)., Conclusions: It was shown that cerebral and muscle oxygenation responses undergo significant changes as work rate increases and show breakpoints in the ongoing response at high intensity (85-95 %VO 2peak ). These breakpoints are strongly interrelated and associated with changes in pulmonary gas exchange.

Purpose: The aim of this project was to study the impact of pedal rate on breakpoints in muscle oxygenation (deoxy[Hb + Mb] and total[Hb + Mb]) and activation (iEMG and MPF) at high intensities during ramp exercise., Methods: Twelve physically active students performed incremental ramp exercises at 60 rpm, starting either at 50 or 80 W (i.e., 60rpm50 and 60rpm80), and at 100 rpm, starting at 50 W (100rpm50). Pulmonary VO2, muscle activation (iEMG and MPF) and oxygenation were recorded with EMG and NIRS, respectively. IEMG, MPF, deoxy[Hb + Mb] and total[Hb + Mb] were expressed as functions of work rate (WR) and pulmonary VO2 (%VO2peak) and analyzed with double-linear models., Results: The breakpoints (BP) of iEMG, MPF, total[Hb + Mb] and deoxy[Hb + Mb] in %VO2peak did not differ among the pedal rate conditions (P > 0.05), whereas the BPs in WR were significantly lower in 100rpm50 compared to 60rpm50 and 60rpm80 (P < 0.01). Across the pedal rate conditions the BP (in %VO2peak) of total[Hb + Mb] (82.7 ± 1.5 %VO2peak) was significantly lower (P < 0.01) compared to the BP in iEMG (84.3 ± 1.7 %VO2peak) and MPF (84.2 ± 1.6 %VO2peak), whereas the BP in deoxy[Hb + Mb] (87.4 ± 1.4 %VO2peak) and respiratory compensation point (89.9 ± 1.8 %VO2peak) were significantly higher (P < 0.01) compared to the BP in total[Hb + Mb], iEMG and MPF. Additionally, the BPs in iEMG, MPF, total[Hb + Mb] and deoxy[Hb + Mb], and the RCP were highly correlated (r > 0.90; P < 0.001)., Conclusions: The present study showed that muscle activation and oxygenation at high intensities during incremental exercise are related to pulmonary VO2 rather than external WR, with a close interrelationship between that muscle activation, oxygenation and pulmonary VO2.

Purpose: Heart rate (HR) is a widespread method to estimate oxygen consumption ( V ˙ O2), exercise intensity, volume, and energy expenditure. Still, accuracy depends on lab tests or using indexes like HRnet and HRindex. This study addresses HR indexes' applicability in postmenopausal women (PMW), who constitute over 50% of the aging population and may have unique characteristics (e.g., heart size) affecting HR use. Methods: Fourteen PMW underwent a cycling ramp incremental test to establish the relationships between V ˙ O2 (in MET) and absolute HR, HRnet, and HRindex. In a second group of ten PMW, population-specific and general equations were tested to predict MET and energy expenditure during six constant work exercises at various intensities. Pulmonary gas exchange and HR were continuously measured using a metabolic cart. Correlations, Bland–Altman analysis, and two-way RM-ANOVA were used to compare estimated and measured values. Results: Strong linear relationships between the three HR indexes and MET were found in Group 1. In Group 2, population-specific equations showed medium-to-high correlations, precision, and no significant biases when estimating MET and energy expenditure. HRnet and HRindex outperformed absolute HR in accuracy. General HR equations had similar correlations but exhibited larger biases and imprecision. Statistical differences between measured and estimated values were observed at all intensities with general equations. Conclusion: This investigation confirms the suitability of HR for estimating aerobic metabolism in one of the most significant aging populations. However, it emphasizes the importance of considering individual variability and developing population-specific models when utilizing HR to infer metabolism. [ABSTRACT FROM AUTHOR]

The aim of this work was to gain more insight into the cardiorespiratory and muscular (m. vastus lateralis) responses to simulated upwind sailing exercise in 10 high-level male and female Optimist sailors (10.8-14.4 years old). Hiking strap load (HSL) and cardiorespiratory variables were measured while exercising on a specially developed Optimist sailing ergometer. Electromyography (EMG) was used to determine mean power frequency (MPF) and root mean square (RMS). Near-infrared spectroscopy was used to measure deoxygenated Hemoglobin and Myoglobin concentration (deoxy[Hb+Mb]) and re-oxygenation. Results indicated that HSL and integrated EMG of the vastus lateralis muscle changed in accordance with the hiking intensity. Cardiorespiratory response demonstrated an initial significant increase and subsequently steady state in oxygen uptake (VO2), ventilation (VE), and heart rate (HR) up to circa 40% VO2peak, 30% VE peak and 70% HRpeak respectively. At muscle level, results showed that highly trained Optimist sailors manage to stabilize the muscular demand and fatigue development during upwind sailing (after an initial increase). However, approaching the end of the hiking exercise, the MPF decrease, RMS increase, and deoxy[Hb+Mb] increase possibly indicate the onset of muscle fatigue. [ABSTRACT FROM AUTHOR]

Purpose: To develop a sailing ergometer that accurately simulates upwind sailing exercise. Methods: A sailing ergometer that measures roll moment accompanied by a biofeedback system that allows imposing a certain quasi-isometric upwind sailing protocol (ie, 18 bouts of 90-s hiking at constantly varying hiking intensity interspersed with 10 s to tack) was developed. Ten male high-level Laser sailors performed an incremental cycling test (ICT; ie, step protocol at 80 W + 40 W/3 min) and an upwind sailing test (UST). During both, heart rate (HR), oxygen uptake (VO2), ventilation (VE), respiratory-exchange ratio, and rating of perceived exertion were measured. During UST, also the difference between the required and produced hiking moment (HM) was calculated as error score (ES). HR, VO2, and VE were calculated relative to their peak values determined during ICT. After UST, the subjects were questioned about their opinion on the resemblance between this UST and real-time upwind sailing. Results: An average HM of 89.0% ± 2.2% HMmax and an average ES of 4.1% ± 1.8% HMmax were found. Mean HR, VO2, and VE were, respectively, 80% ± 4% HRpeak, 39.5% ± 4.5% VO2peak, and 30.3% ± 3.7% VEpeak. Both HM and cardiorespiratory values appear to be largely comparable to literature reports during on-water upwind sailing. Moreover, the subjects gave the upwind sailing ergometer a positive resemblance score. Conclusions: Results suggest that this ergometer accurately simulates on-water upwind sailing exercise. As such, this ergometer could be a great help in performance diagnostics and training follow-up. [ABSTRACT FROM AUTHOR]

We investigated the impact of ramp and constant-load exercise on (i) respiratory muscle fatigue and locomotor muscle oxygenation, (ii) their relationship with the excess VO 2 and VO 2 slow component (SC). Fourteen male cyclists performed two tests to exhaustion: an incremental ramp and a constant-load exercise with continuous monitoring of expired gases and oxygenation of the vastus lateralis muscle on two separate days. Maximal inspiratory (MIP) and expiratory (MEP) pressure measurements were taken at rest and post- exercise. The VO 2 excess represents the difference between VO 2max observed and VO 2max expected using linear equation between the VO 2 and the intensity before gas-exchange threshold. During the ramp exercise, MIP and MEP declined by 13 ± 8 and 19 ± 10%, respectively (p < 0.05). MIP and MEP were not correlated to the excess VO 2 (0.09 ± 0.05 l min −1 ). During the constant-load exercise, the VO 2 SC (0.70 ± 0.22 l min −1 ) was correlated (r = 0.68, p < 0.01) to deoxyhemoglobin SC (2.94 ± 1.25 A U) but not to the excess VO 2 (r = 0.30, p = 0.2). Additionally, the significant decrease in MIP (20 ± 9%) and MEP (23 ± 11%) was correlated (r = 0.55, p < 0.05 and r = 0.75, p < 0.05, respectively) to the VO 2 SC. Our results show that respiratory muscle fatigue was correlated to the VO 2 SC in the constant-load exercise, whereas it was not correlated to the excess VO 2 in ramp exercise may be because of our small excess VO 2 . [ABSTRACT FROM AUTHOR]

This study investigates the physiological responses to upwind sailing on a laser emulation ergometer and analyses the components of the physical profile that determine the physiological responses related to sailing level. Ten male high-level laser sailors performed an upwind sailing test, incremental cycling test and quadriceps strength test. During the upwind sailing test, heart rate (HR), oxygen uptake, ventilation, respiratory exchange ratio, rating of perceived exertion (RPE) and lactate concentration were measured, combined with near-infrared spectroscopy (NIRS) and electromyography (EMG) registration of the M. Vastus lateralis. Repeated measures ANOVA showed for the cardio-respiratory, metabolic and muscles responses (mean power frequency [MPF], root mean square [RMS], deoxy[Hb+Mb]) during the upwind sailing test an initial significant increase followed by a stabilisation, despite a constant increase in RPE. Stepwise regression analysis showed that better sailing level was for 46.5% predicted by lower MPF decrease. Lower MPF decrease was for 57.8% predicted by a higher maximal isometric quadriceps strength. In conclusion, this study indicates that higher sailing level was mainly determined by a lower rate of neuromuscular fatigue during the upwind sailing test (as indicated by MPF decrease). Additionally, the level of neuromuscular fatigue was mainly determined by higher maximal isometric quadriceps strength stressing the importance of resistance training in the planning of training. [ABSTRACT FROM PUBLISHER]

This article is a commentary to the original article https://doi.org/10.1007/s00424-020-02487-x In the past 30 years, mathematical modelling of the VO SB 2 sb response during metabolic transitions (i.e. VO SB 2 sb kinetics) by a sequence of first-order exponential functions has offered a non-invasive means to probe the physiological mechanisms of O SB 2 sb delivery and utilization [[7], [10]]. This observation is compatible with the intuition of Pereira de Lima et al. [[5]] that the VO SB 2 sb profile observed at exercise onset may be the result of the integrated response of the two muscle fibre populations with different kinetics [[4], [6]]. Second-order modeling for the pulmonary oxygen uptake on-kinetics: comprehensive solution for overshooting and nonovershooting responses to exercise. [Extracted from the article]

An incremental ramp exercise is a protocol that is frequently used in the domain of exercise testing to get an insight into the exercise tolerance of both healthy active populations (including athletes) and patients, due to the specific characteristics of the protocol. The continuous and linear increase in work rate is not only less strenuous for populations with a very low exercise capacity but it requires the aerobic metabolism to adapt to the continuously changing conditions. Therefore, this protocol can provide important information on the adaptive capacity of individuals to exercise in non-steadystate conditions. The ramp exercise has also been used in the past two decades to get an insight into the underlying mechanisms of the oxygen uptake (VO2) response (and kinetics) to exercise. Against the expectations, it has been shown that the parameters that quantify the VO2 response to ramp exercise do not completely correspond to those obtained from constant work-rate transitions and incremental step exercise. For that reason, it could be concluded that the VO2 response is specific to ramp exercise, and thus is determined by other mechanisms than those which determine other protocols. Although the VO2 response to ramp exercise has a high level of reproducibility and a uniform pattern can be observed, especially for the VO2 response below the gas exchange threshold (GET) [above the GET, the VO2 response is less clear], some prudence is necessary when interpreting potential differences in the VO2 response between populations. Several methodological issues (e.g. baseline work rate, ramp slope) exert an important impact on the VO2 response to ramp exercise. The main purpose of this review is to provide an overview of the methodological and physiological factors that have an impact on the VO2 response to ramp exercise. It is of importance that exercise physiologists take these factors into consideration, not only prior to the conductance of the ramp exercise in a variety of subjects, but also when interpreting the obtained results. [ABSTRACT FROM AUTHOR]

The article presents a study that aims to test the comparability of the oxygen uptake and work rate relationship between aerobically trained and less trained subjects during ramp protocol related to muscle fiber activation changes. It says that the oxygen uptake response during incremental exercise provides information on both the functioning aerobic metabolism and its capacity to adjust to metabolic demand changes in healthy and unhealthy populations. The study used cyclists and physically active (PA) students to perform ramp exercises and a step protocol and measured the pulmonary gas exchange and muscle fiber activity. Results reveal higher oxygen uptake and work rate relationship in cyclists concluding that the cyclists show reduced mechanical efficiency during ramp protocol.

Abstract: The aim of the study was to test whether ramp slope and training status interact in the oxygen uptake () response during submaximal ramp exercise. Eight cyclists ( peak=67.8±3.7mlmin−1 kg−1) and eight physically active students (PA students) ( peak=49.1±4.3mlmin−1 kg−1) performed several ramp protocols, respectively, 25 and 40Wmin−1 for the cyclists and 10, 25 and 40Wmin−1 for the PA students. was plotted as a function of time and work rate up to the gas exchange threshold (GET). Faster ramp elicited a significantly shorter mean response time (MRT) in both groups, and MRT was significantly longer for each ramp protocol in the PA students (126±32s, 76±15s and 50±6s for ramp 10, ramp 25 and ramp 40, respectively) compared to the cyclists (61±9s and 40±11s for ramp 25 and ramp 40, respectively). Ramp 40 showed less steep than ramp 25 in both groups (p <0.01) and was less steep for each ramp protocol in PA students (p <0.01) (9.82±0.30mlmin−1 W−1 and 9.33±0.45mlmin−1 W−1 for ramp 25 and ramp 40, respectively) compared to cyclists (10.31±0.40mlmin−1 W−1 and 10.05±0.48mlmin−1 W−1 for ramp 25 and ramp 40, respectively). In the PA students, did not differ between ramp 10 and ramp 25. Statistical analysis showed no interaction effects between ramp slope and training status for MRT (p =0.62) and (p =0.35). [Copyright &y& Elsevier]

Purpose: The aims of this study were 1) to model the temporal profile of W' recovery after exhaustion, 2) to estimate the contribution of changing ...O2 kinetics to this recovery, and 3) to examine associations with aerobic fitness and muscle fiber type (MFT) distribution. Methods: Twenty-one men (age = 25 ± 2 yr, ...O2peak = 54.4 ± 5.3 mL⋅min-1⋅kg-1) performed several constant load tests to determine critical power and W' followed by eight trials to quantify W' recovery. Each test consisted of two identical exhaustive work bouts (WB1 and WB2), separated by a variable recovery interval of 30, 60, 120, 180, 240, 300, 600, or 900 s. Gas exchange was measured and muscle biopsies were collected to determine MFT distribution. W' recovery was quantified as observed W' recovery (W'OBS), model-predicted W' recovery (W'BAL), and W' recovery corrected for changing ...O2 kinetics (W'ADJ). W'OBS and W'ADJ were modeled using mono- and biexponential fitting. Root-mean-square error (RMSE) and Akaike information criterion (ΔAICC) were used to evaluate the models' accuracy. Results: The W'BAL model (τ = 524 ± 41 s) was associated with an RMSE of 18.6% in fitting W'OBS and underestimated W' recovery for all durations below 5 min (P < 0.002). Monoexponential modeling of W'OBS resulted in τ = 104 s with RMSE = 6.4%. Biexponential modeling of W'OBS resulted in τ1 = 11 s and τ2 = 256 s with RMSE = 1.7%. W'ADJ was 11% ± 1.5% lower than W'OBS (P < 0.001). ΔAICC scores favored the biexponential model for W'OBS, but not for W'ADJ. ...O2peak (P = 0.009) but not MFT distribution (P = 0.303) was associated with W'OBS. Conclusion: We showed that W' recovery from exhaustion follows a two-phase exponential time course that is dependent on aerobic fitness. The appearance of a fast initial recovery phase was attributed to an enhanced aerobic energy provision resulting from changes in ...O2 kinetics. [ABSTRACT FROM AUTHOR]

Purpose: Intense exercise evokes a spleen contraction releasing red blood cells into blood circulation. The same mechanism is found after acute apnea, increasing hemoglobin concentration ([Hb]) by 2% to 5%. The aim of this study was twofold: [1] to identify the optimal apnea modalities to acutely increase [Hb] and [2] use these modalities to examine whether prerace apnea can improve a 3-km time trial (TT). Methods: In part 1, 11 male subjects performed 12 different apnea protocols based on three modalities: mode, frequency, and intensity. Venous blood samples for [Hb] were collected before, immediately, and 5 min after each protocol. In part 2, 12 recreationally active subjects performed 3-km cycling TT in three different conditions: apnea, control, and placebo, after a 10-min warm-up. Power output, HR, and oxygen uptake (V˙O2) were continuously measured. Venous [Hb] was sampled at baseline, after warm-up, and before TT. Additionally, these subjects performed constant cycling at Δ25 (25% between gas exchange threshold and V˙O2 max) in two conditions (control and apnea) to determine V˙O2 kinetics. Results: Although including one single apnea in the warming up evoked a positive change in [Hb] pattern (P = 0.049) and one single apnea seemed to improve V˙O2 kinetics in constant submaximal cycling (τ: P = 0.060, mean response time: P = 0.064), performance during the 3-km TT did not differ between conditions (P = 0.840; apnea, 264.8 ± 14.1 s; control, 263.9 ± 12.9 s, placebo, 264.0 ± 15.8 s). Average normalized power output (P = 0.584) and V˙O2, HR, and lactate did not differ either (P > 0.05). Conclusions: These results suggest that potential effects of apnea, that is, speeding of V˙O2 kinetics through a transient increase in [Hb], are overruled by a warming-up protocol. [ABSTRACT FROM AUTHOR]

The article examines one study which investigates whether L-arginine administration could slow down the pulmonary oxygen uptake kinetics of humans at the onset of moderate-intensity exercise. Seven physically active males were divided into two; one group was to take placebo while the other group was to take L-arginine hydrochloride capsules. They were also asked to complete two consecutive six-minute bouts of cycle exercise at 80 percent of the ventilatory threshold with a 12-minute rest interval. After data analysis, it was revealed that the drug could speed the phase II pulmonary oxygen uptake response by 12 percent at the onset of the said exercise in humans.