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Aim: A 15-s all-out sprint cycle test (i.e., νLamax-test) and the post-exercise change in capillary blood lactate concentration is an emerging diagnostic tool that is used to quantify the maximal glycolytic rate. The goal of this study was to determine the relation between 15 s-work, change in capillary blood lactate concentration (∆La) and body composition in a νLamax-test. Method: Fifty cyclists performed a 15 s all-out sprint test on a Cyclus2 ergometer twice after a previous familiarization trial. Capillary blood was sampled before and every minute (for 8 min) after the sprint to determine ∆La. Body composition was determined employing InBody720 eight-electrode impedance analysis. Result: Simple regression models of fat-free mass (FFM) and also the product of FFM and ∆La showed similar ability to predict 15 s-work (R2 = 0.79; 0.82). Multiple regression combining both predictors explains 93% of variance between individuals. No differences between males and females were found regarding 15 s-work relative to the product of fat-free mass and ∆La. Considering pairs of similar FFM, a change 1 mmol/l of ∆La is estimated to be equal to 12 J/kg in 15 s-work (R2 = 0.85). Discussion: Fifteen s-work is both closely related to FFM and also the product of ∆La and lactate-distribution space approximated by FFM. Differences in 15 s-work between males and females disappear when total lactate production is considered. Considering interindividual differences, the mechanical energy equivalent of blood lactate accumulation seems a robust parameter displaying a clear relationship between ∆La and 15 s-work relative to FFM. [ABSTRACT FROM AUTHOR]

Purpose: Apnea duration is dependent on three factors: oxygen storage, oxygen consumption, hypoxia and hypercapnia tolerance. While current literature focuses on maximal apneas to improve apnea duration, apnea trained individuals use timed-repeated submaximal apneas, called "O2 and CO2 tables". These tables claim to accommodate the body to cope with hypoxia and hypercapnia, respectively. The aim of this study was twofold. First, to investigate the determinants of maximal apnea duration in apnea novices. Second, to compare physiologic responses to maximal apneas, O2 and CO2 tables. Methods: After medical screening, lung function test and hemoglobin mass measurement, twenty-eight apnea novices performed three apnea protocols in random order: maximal apneas, O2 table and CO2 table. During apnea, peripheral oxygen saturation (SpO2), heart rate (HR), muscle (mTOI) and cerebral (cTOI) tissue oxygenation index were measured continuously. End-tidal carbon dioxide (EtCO2) was measured before and after apneas. Results: Larger lung volumes, higher resting cTOI and lower resting EtCO2 levels correlated with longer apnea durations. Maximal apneas induced greater decreases in SpO2 (− 16%) and cTOI (− 13%) than O2 (− 8%; − 8%) and CO2 tables (− 6%; − 6%), whereas changes in EtCO2, HR and mTOI did not differ between protocols. Conclusion: These results suggest that, in apnea novices, O2 and CO2 tables did not induce a more profound hypoxia and hypercapnia, but a similar reduction in oxygen consumption than maximal apneas. Therefore, apnea novices should mainly focus on maximal apneas to improve hypoxia and hypercapnia tolerance. The use of specific lung training protocols can help to increase oxygen storage capacity. [ABSTRACT FROM AUTHOR]

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]

Purpose: The aim of this study was to compare critical power (CP) and work capacity W′, and W′ reconstitution (W′REC) following repeated maximal exercise between women and men. Methods: Twelve women ( V ˙ O2PEAK: 2.53 ± 0.37 L·min−1) and 12 men ( V ˙ O2PEAK: 4.26 ± 0.30 L·min−1) performed a minimum of 3 constant workload tests, to determine CP and W′, and 1 maximal exercise repetition test with three work bouts (WB) to failure, to quantify W′REC during 2 recovery periods, i.e., W′REC1 and W′REC2. An independent samples t test was used to compare CP and W′ values between women and men, and a repeated-measures ANOVA was used to compare W′REC as fraction of W′ expended during the first WB, absolute W′REC, and normalized to lean body mass (LBM). Results: CP normalized to LBM was not different between women and men, respectively, 3.7 ± 0.5 vs. 4.1 ± 0.4 W·kgLBM−1, while W′ normalized to LBM was lower in women 256 ± 29 vs. 305 ± 45 J·kgLBM−1. Fractional W′REC1 was higher in women than in men, respectively, 74.0 ± 12.0% vs. 56.8 ± 9.5%. Women reconstituted less W′ than men in absolute terms (8.7 ± 1.2 vs. 10.9 ± 2.0 kJ) during W′REC1, while normalized to LBM no difference was observed between women and men (174 ± 23 vs. 167 ± 31 J·kgLBM−1). W′REC2 was lower than W′REC1 both in women and men. Conclusion: Sex differences in W′REC (absolute women < men; fractional women > men) are eliminated when LBM is accounted for. Prediction models of W′REC might benefit from including LBM as a biological variable in the equation. This study confirms the occurrence of a slowing of W′REC during repeated maximal exercise. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to examine how respiratory (RT) and lactate thresholds (LT) are affected by acute heat exposure in the two most commonly used incremental exercise test protocols (RAMP and STEP) for functional evaluation of aerobic fitness, exercise prescription and monitoring training intensities. Methods: Eleven physically active male participants performed four incremental exercise tests, two RAMP (30 W·min−1) and two STEP (40 W·3 min−1), both in 18 °C (TEMP) and 36 °C (HOT) with 40% relative humidity to determine 2 RT and 16 LT, respectively. Distinction was made within LT, taking into account the individual lactate kinetics (LTIND) and fixed value lactate concentrations (LTFIX). Results: A decrease in mean power output (PO) was observed in HOT at LT (−6.2 ± 1.9%), more specific LTIND (−5.4 ± 1.4%) and LTFIX (−7.5 ± 2.4%), compared to TEMP, however not at RT (−1.0 ± 2.7%). The individual PO difference in HOT compared to TEMP over all threshold methods ranged from −53 W to +26 W. Mean heart rate (HR) did not differ in LT, while it was increased at RT in HOT (+10 ± 8 bpm). Conclusion: This study showed that exercise thresholds were affected when ambient air temperature was increased. However, a considerable degree of variability in the sensitivity of the different threshold concepts to acute heat exposure was found and a large individual variation was noticed. Test design and procedures should be taken into account when interpreting exercise test outcomes. [ABSTRACT FROM AUTHOR]

Purpose: This study longitudinally examined the interchangeable use of critical power (CP), the maximal lactate steady state (MLSS) and the respiratory compensation point (RCP) (i.e., whole-body thresholds), and breakpoints in muscle deoxygenation (m[HHb]BP) and muscle activity (iEMGBP) (i.e., local thresholds). Methods: Twenty-one participants were tested on two timepoints (T1 and T2) with a 4-week period (study 1: 10 women, age = 27 ± 3 years, V ˙ O 2 peak = 43.2 ± 7.3 mL min−1kg−1) or a 12-week period (study 2: 11 men, age = 25 ± 4 years, V ˙ O 2 peak = 47.7 ± 5.9 mL min−1 kg−1) in between. The test battery included one ramp incremental test (to determine RCP, m[HHb]BP and iEMGBP) and a series of (sub)maximal constant load tests (to determine CP and MLSS). All thresholds were expressed as oxygen uptake ( V ˙ O 2 ) and equivalent power output (PO) for comparison. Results: None of the thresholds were significantly different in study 1 ( V ˙ O 2 : P = 0.143, PO: P = 0.281), but differences between whole-body and local thresholds were observed in study 2 ( V ˙ O 2 : P < 0.001, PO: P = 0.024). Whole-body thresholds showed better 4-week test–retest reliability (TEM = 88–125 mL min−1 or 6–10 W, ICC = 0.94–0.98) compared to local thresholds (TEM = 189–195 mL min−1 or 15–18 W, ICC = 0.58–0.89). All five thresholds were strongly associated at T1 and T2 (r = 0.75–0.99), but their changes from T1 to T2 were mostly uncorrelated (r = − 0.41–0.83). Conclusion: Whole-body thresholds (CP/MLSS/RCP) showed a close and consistent coherence taking into account a 3–6%-bandwidth of typical variation. In contrast, local thresholds (m[HHb]BP/iEMGBP) were characterized by higher variability and did not consistently coincide with the whole-body thresholds. In addition, we found that most thresholds evolved independently of each other over time. Together, these results do not justify the interchangeable use of whole-body and local exercise thresholds in practice. [ABSTRACT FROM AUTHOR]

Purpose: The aims of this study were (1) to investigate if the respiratory compensation point (RCP) as derived from ramp incremental (RI) exercise could accurately predict the power output (PO) at the maximal lactate steady state (MLSS), and (2) to compare its accuracy with the second lactate threshold (LT2) obtained from step incremental (SI) exercise.Methods: Nineteen participants performed a RI test (30 W·min-1) to determine RCP, a SI test (30 or 40 W·3 min-1) to determine LT2, and two or more constant work rate (CWR) tests to determine MLSS. For each participant, the [Formula: see text]O2/PO relationship for RI and CWR exercise was established. The ramp-identified PO at RCP was corrected by accounting for the gap between these relationships using the individually determined [Formula: see text] O2/PO regression above GET (RCPcorr-1) or using a fixed regression slope (RCPcorr-2). LT2 was determined using four methods: Dmax, modified Dmax (ModDmax), 4-mM threshold (LT4mM) and an expert-determined LT2 (LT2-expert).Results: RCPcorr-1 (235 ± 69 W), RCPcorr-2 (228 ± 58 W) and LT2-expert (227 ± 61 W) were not different from MLSS (225 ± 60 W). Dmax (203 ± 53 W) underestimated MLSS, while RCP (280 ± 60 W), ModDmax (235 ± 67 W) and LT4mM (234 ± 68 W) overestimated MLSS. The [Formula: see text]O2 at RCP (3.13 ± 0.79L·min-1) and LT2-expert (2.99 ± 0.19L·min-1) did not differ from MLSS (3.05 ± 0.72 L·min-1).Conclusion: This study demonstrated that RCP as derived from RI exercise and LT2 as derived from SI exercise can be equally accurate to determine the PO associated with MLSS. Although these results confirmed the suitability of RI and SI tests for this purpose, they also highlighted the importance of an appropriate threshold method selection and the eye of the expert. [ABSTRACT FROM AUTHOR]

This study focused on the steady-state phase of exercise to evaluate the relative contribution of metabolic instability (measured with NIRS and haematochemical markers) and muscle activation (measured with EMG) to the oxygen consumption ( V ˙ O 2 ) slow component ( V ˙ O 2 s c ) in different intensity domains. We hypothesized that (i) after the transient phase, V ˙ O 2 , metabolic instability and muscle activation tend to increase differently over time depending on the relative exercise intensity and (ii) the increase in V ˙ O 2 s c is explained by a combination of metabolic instability and muscle activation. Eight active men performed a constant work rate trial of 9 min in the moderate, heavy and severe intensity domains. V ˙ O 2 , root mean square by EMG (RMS), deoxyhaemoglobin by NIRS ([HHb]) and haematic markers of metabolic stability (i.e. [La−], pH, HCO3−) were measured. The physiological responses in different intensity domains were compared by two-way RM-ANOVA. The relationships between the increases of [HHb] and RMS with V ˙ O 2 after the third min were compared by simple and multiple linear regressions. We found domain-dependent dynamics over time of V ˙ O 2 , [HHb], RMS and the haematic markers of metabolic instability. After the transient phase, the rises in [HHb] and RMS showed medium–high correlations with the rise in V ˙ O 2 ([HHb] r = 0.68, p < 0.001; RMS r = 0.59, p = 0.002). Moreover, the multiple linear regression showed that both metabolic instability and muscle activation concurred to the V ˙ O 2 s c (r = 0.75, [HHb] p = 0.005, RMS p = 0.042) with metabolic instability possibly having about threefold the relative weight compared to recruitment. Seventy-five percent of the dynamics of the V ˙ O 2 s c was explained by [HHb] and RMS. [ABSTRACT FROM AUTHOR]

During heavy and severe constant-load exercise, VO2 displays a slow component (VO2sc) typically interpreted as a loss of efficiency of locomotion. In the ongoing debate on the underpinnings of the VO2sc, recent studies suggested that VO2sc could be attributed to a prolonged shift in energetic sources rather than loss of efficiency. We tested the hypothesis that the total cost of cycling, accounting for aerobic and anaerobic energy sources, is affected by time during metabolic transitions in different intensity domains. Eight active men performed 3 constant load trials of 3, 6, and 9 min in the moderate, heavy, and severe domains (i.e., respectively below, between, and above the two ventilatory thresholds). VO2, VO2 of ventilation and lactate accumulation ([La−]) were quantified to calculate the adjusted oxygen cost of exercise (AdjO2Eq, i.e., measured VO2 − VO2 of ventilation + VO2 equivalent of [La−]) for the 0–3, 3–6, and 6–9 time segments at each intensity, and compared by a two-way RM-ANOVA (time × intensity). After the transient phase, AdjO2Eq was unaffected by time in moderate (ml*3 min−1 at 0–3, 0–6, 0–9 min: 2126 ± 939 < 2687 ± 1036, 2731 ± 1035) and heavy (4278 ± 1074 < 5121 ± 1268, 5225 ± 1123) while a significant effect of time was detected in the severe only (5863 ± 1413 < 7061 ± 1516 < 7372 ± 1443). The emergence of the VO2sc was explained by a prolonged shift between aerobic and anaerobic energy sources in heavy (VO2 − VO2 of ventilation: ml*3 min−1 at 0–3, 0–6, 0–9 min: 3769 ± 1128 < 4938 ± 1256, 5091 ± 1123, [La−]: 452 ± 254 < 128 ± 169, 79 ± 135), while a prolonged metabolic shift and a true loss of efficiency explained the emergence of the VO2sc in severe. [ABSTRACT FROM AUTHOR]

Purpose: Acute breath-holding deprives the human body from oxygen. In an effort to protect the brain, the diving response is initiated, coupling several physiological responses. The aim of this study was to describe the physiological responses to apnea at the cardiac, peripheral and cerebral level. Methods: 31 physically active subjects (17 male, 14 female, 23.3 ± 1.8 years old) performed a maximal static breath-hold in a seated position. Heart rate (HR), muscle and cerebral oxygenation (by means of near-infrared spectroscopy, NIRS) were continuously measured. RM MANOVA's were used to identify changes in HR, peripheral (mTOI) and cerebral (cTOI) tissue oxygenation and oxygenated (O2Hb) and deoxygenated (HHb) hemoglobin during apnea. Results: Average apnea duration was 157 ± 41 s. HR started decreasing after 10 s (p < 0.001) and dropped on average by 27 ± 14 bpm from baseline (p < 0.001). mTOI started decreasing 10 s after apnea (p < 0.001) and fell by 8.6 ± 4.0% (p < 0.001). Following an immediate drop after 5 s (p < 0.001), cTOI increased continuously, reaching a maximal increase of 3.7 ± 2.4% followed by a steady decrease until the end of apnea. cTOI fell on average 5.4 ± 8.3% below baseline (p < 0.001). Conclusion: During apnea, the human body elicits several protective mechanisms to protect itself against the deprivation of oxygen. HR slows down, decreasing O2 demand of the cardiac muscle. The decrease in mTOI and increase in cTOI imply a redistribution of blood flow prioritizing the brain. However, this mechanism is not sufficient to maintain cTOI until the end of apnea. [ABSTRACT FROM AUTHOR]

For the same reasons, we totally agree with Goulding et al. that extrapolating local thresholds as if they reflect the whole-body physiological response would be too simplistic. We would like to thank Goulding et al.([5]) for the insights they provided in their letter to the editor, submitted in response to our longitudinal study on the interchangeable use of whole-body and local exercise thresholds (Caen et al. [3]). [Extracted from the article]

This study evaluates the impact of antibiotic treatments and hospitalization on exercise performance and health-related quality of life (QOL) in children with mild cystic fibrosis (CF) lung disease. Forty-seven children between 7 and 17 years with mild CF underwent a maximal exercise test including spiro-ergometry and filled out a QOL-questionnaire (PedsQL™). Amount of antibiotic treatments (AB) and hospitalization days in the last 3 years were reviewed. FEV1% was mildly decreased (91.7 ± 17.9 L/min, p = 0.02). Maximal oxygen consumption (VO2max), test duration and anaerobic threshold were lower compared to a control population (VO2max% 94 ± 15 vs 103 ± 13, p = 0.009). FEV1% correlated with AB and hospitalization episodes in the last year and 3 years before testing, VO2max% only correlated with AB in the last 3 years. Domains of school functioning and emotional functioning were low. Children with higher VO2max% and less AB in the last 3 years had better physical health. Physical health and school functioning were negatively correlated with hospitalization days in the last year.Conclusion: Patients with mild CF lung disease have good exercise performance although still lower than the normal population. VO2max% is affected by number of antibiotic treatments over a longer period. There is an impact of hospitalization days on quality of life. What is Known: • Children with CF have lower exercise performance; there is an association between hospitalization frequency and exercise performance • Quality of life is diminished in children with CF and influenced by respiratory infections What is New: • Even patients with mild CF lung disease have lower maximal exercise performance (VO 2 max) and a lower anaerobic threshold; VO 2 max is lower in children who had more antibiotic treatments in the last 3 years • School and emotional functioning are diminished in children with mild CF lung disease; hospitalization is negatively correlated with school functioning and physical functioning. [ABSTRACT FROM AUTHOR]

In the past two decades oxygenation responses to incremental ramp exercise, measured non-invasively by means of near-infrared spectroscopy at different locations in the body, have advanced the insights on the underpinning mechanisms of the whole-body pulmonary oxygen uptake ( $$\dot{V}{\text{O}}_{2}$$ ) response. In healthy subjects the complex oxygenation responses at the level of locomotor and respiratory muscles, and brain were simplified and quantified by the detection of breakpoints as a deviation in the ongoing response pattern as work rate increases. These breakpoints were located in a narrow intensity range between 75 and 90 % of the maximal $$\dot{V}{\text{O}}_{2}$$ and were closely related to traditionally determined thresholds in pulmonary gas exchange (respiratory compensation point), blood lactate measurements (maximal lactate steady state), and critical power. Therefore, it has been assumed that these breakpoints in the oxygenation patterns at different sites in the body might be equivalent and could, therefore, be used interchangeably. In the present review the typical oxygenation responses (at locomotor and respiratory muscle level, and cerebral level) are described and a possible framework is provided showing the physiological events that might link the breakpoints at different body sites with the thresholds determined from pulmonary gas exchange and blood lactate measurements. However, despite a possible physiological association, several arguments prevent the current practical application of these breakpoints measured at a single site as markers of exercise intensity making it highly questionable whether measurements of the oxygenation response at one single site can be used as a reflection of whole-body responses to different exercise intensities. [ABSTRACT FROM AUTHOR]

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 (OHb) and deoxygenated (HHb) hemoglobin (by means of near-infrared spectroscopy) and pulmonary gas exchange was recorded. Cerebral and muscle OHb and HHb values were expressed as functions of oxygen uptake ( VO) and breakpoints were detected by means of double linear model analysis. The respiratory compensation point (RCP) was determined. The breakpoints in cerebral and muscle OHb and HHb were compared and correlated to RCP. Results: The subjects reached peak power output of 105 ± 18 W and VO of 43.5 ± 7.0 ml min kg. Cerebral OHb increased to an intensity of 89.4 ± 5.5 % VO, where a breakpoint occurred at which cerebral OHb started to decrease. Cerebral HHb increased slightly to 88.1 ± 4.8 % VO, at which the increase was accelerated. Muscle HHb increased to 90.5 ± 4.8 % VO where a leveling-off occurred. RCP occurred at 89.3 ± 4.3 % VO. 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 ( 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). These breakpoints are strongly interrelated and associated with changes in pulmonary gas exchange. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to compare the muscle oxygenation between trained and untrained subjects during heavy exercise until exhaustion at two extreme pedaling cadences using a NIRS system.Methods: Nine untrained male subjects and nine male competitive triathletes cycled until exhaustion at an intensity corresponding to 90 % of the power output achieved at peak oxygen uptake at 40 and 100 rpm. Gas exchanges were measured breath-by-breath during each exercise. Muscle (de)oxygenation was monitored continuously by near-infrared spectroscopy on the Vastus Lateralis.Results: Muscle deoxygenation (∆deoxy[Hb + Mb], i.e., O2 extraction) and ∆total[Hb + Mb] were significantly higher at 40 rpm compared to 100 rpm during the exercise in untrained subjects but not in triathletes (p < 0.05). The time performed until exhaustion was significantly higher at 40 than at 100 rpm in untrained subjects (373 ± 55 vs. 234 ± 37 s, respectively) but not in triathletes (339 ± 69 vs. 325 ± 66 s).Conclusions: These results indicate that high aerobic fitness (1) allows for better regulation between [Formula: see text]O2M and VO2M following the change in pedaling cadence, and (2) is the most important factor in the relationship between pedaling cadence and performance. [ABSTRACT FROM AUTHOR]

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 VO, 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 VO (% VO) and analyzed with double-linear models. Results: The breakpoints (BP) of iEMG, MPF, total[Hb + Mb] and deoxy[Hb + Mb] in % VO 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 % VO) of total[Hb + Mb] (82.7 ± 1.5 % VO) was significantly lower ( P < 0.01) compared to the BP in iEMG (84.3 ± 1.7 % VO) and MPF (84.2 ± 1.6 % VO), whereas the BP in deoxy[Hb + Mb] (87.4 ± 1.4 % VO) and respiratory compensation point (89.9 ± 1.8 % VO) 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 VO rather than external WR, with a close interrelationship between that muscle activation, oxygenation and pulmonary VO. [ABSTRACT FROM AUTHOR]

Kitesurfing is a relatively new extreme water sport that is considered a high-risk sport and has rising popularity. Kitesurfing combines aspects of several water sports, including surfing, windsurfing, and wakeboarding. With a large controllable kite and a small board, kitesurfers travel over the water surface with speeds of up to 35 knots. The vertical lift of the kite makes it possible to perform jumps up to 15 m high and 30 m long, while doing different manoeuvres in the air. Few scientific data are available concerning the biomechanical and physiological demands of kitesurfing and the epidemiology of kitesurfing injury, and research methods used are often questionable. During kitesurfing, considerable stress is placed on the musculoskeletal and physiological systems, and the possibility of injury or fatality is an inherent part of participation. The lower back and thigh muscles are often perceived as being highly stressed, while abdominal muscles, knees, and feet are common sites of pain or discomfort. During kitesurfing, both aerobic and anaerobic metabolism contribute to energy delivery. It is reported in the literature that kitesurfing injuries are mainly acute, due to accidents or trauma. Non-competitive kitesurfing resulted in an overall injury rate of 5.9-7.0 injuries per 1,000 kitesurfing hours. It seems that the risk of injury increases dramatically in competitive kitesurfing. However, contradictory results have been found. Lower extremities were the most common major site of injuries, followed by upper extremities, trunk, and head. Most accidents during kitesurfing reported in the literature were attributed to the inability to detach the kite from the harness. Due to technical innovations, recent studies report uncontrolled actions and unsuccessful tricks and jumps with poor landings as the main mechanisms of injuries. The main purpose of the present paper is to critically analyse the current relevant scientific literature on the biomechanical and physiological demands of kitesurfing and the epidemiology of injury among kitesurfers, in order to obtain greater insights into (i) the stresses imposed on the musculoskeletal and physiological systems by kitesurfing, and (ii) the rate, pattern, and mechanisms of kitesurfing injuries. [ABSTRACT FROM AUTHOR]

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]

In order to investigate the interaction between tax policy, welfare benefits, the government technology for monitoring and sanctioning inadequate search, workfare, and externalities from work, we incorporate endogenous job search and involuntary unemployment into a model of optimal nonlinear income taxation. In this setting, the government faces a trade-off between boosting employment of low-skilled agents and raising work effort of high-skilled workers. If sanctions for inadequate search effort can be targeted at high productivity types for whom it is socially optimal to search, the government can afford to levy higher labor taxes on marginal workers without discouraging these agents from seeking work. This allows for lower marginal taxes on work effort of agents with a job. In contrast to workfare, job externalities in the private sector raise marginal tax rates, as the government attaches more importance to boosting employment of low-skilled workers. [ABSTRACT FROM AUTHOR]

The price cost margin (PCM) is a popular way to measure competition. Although we know that this measure is not without problems, we actually do not know how often and under which conditions a change in PCM points in the wrong direction. We use a newcompetitionmeasure, the profit elasticity,which is more robust than PCM. Our empirical analysis based on Dutch data shows that when competition changes the probability that PCM points in the wrong direction increases with industry concentration. [ABSTRACT FROM AUTHOR]

Putting a limit on the duration of unemployment benefits tends to introduce a 'spike' in the job finding rate shortly before benefits are exhausted. Current theories explain this spike from workers' behavior. We present a theoretical model in which also the nature of the job matters. End-of-benefit spikes in job finding rates are related to optimizing behavior of unemployed workers who rationally assume that employers will accept delays in the starting date of a new job, especially if these jobs are permanent. This gives some workers an incentive to not immediately start working after they have found a job. Instead they wait until their benefits expire. We use a dataset on Slovenian unemployment spells to test this prediction and find supporting evidence. We conclude that the spike in the job finding rate suggests that workers exploit unemployment insurance benefits for subsidized leisure. [ABSTRACT FROM AUTHOR]

The purpose of this study was to test the reliability of a new handgrip exercise protocol measuring forearm oxygenation in 20 healthy subjects on two occasions. The retest took place 48 h later and at the same time of the day. The incremental exercise consisted of 2 min steps of cyclic handgrip contraction (1/2 Hz) separated by 1 min of recovery. The exercise started at 20% MVC, was increased with 10% MVC each step and was performed until exhaustion (69.5 and 73% MVC). Near infrared spectroscopy (NIRS) was used to measure deoxygenation (deoxy[Hb + Mb]) and oxygen saturation (SmO) in the forearm muscles. Prior to the exercise protocol an arterial occlusion of the forearm was performed until deoxy(Hb + Mb) did no longer increase. Maximal increase in deoxy[Hb + Mb] during 10 s of each exercise bout was expressed relative to the occlusion amplitude. ICC was used to examine the test-retest reliability. Significant ICC's were reported at 50% ( r = 0.466, p = 0.017) and 60% MVC ( r = 0.553, p = 0.005). The group mean of the maximum increase in oxygen extraction was 45.6 ± 16.7% and at the retest 44.9 ± 17.0% with an ICC of r = 0.867 ( p < 0.001) which could be classified (Landis and Koch 1979) as almost perfect. The absolute SmO values showed reliable ICC's for every submaximal intensity except at 60% MVC. An ICC of r = 0.774 ( p < 0.001) was found at maximal intensity. The results of the present study show that deoxy[Hb + Mb] and SmO responses during this protocol are highly reliable and indicate that this protocol could be used to get insight into deoxygenation and oxygen saturation in a population with low exercise tolerance. [ABSTRACT FROM AUTHOR]

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 aim of the present study was to gain better insight into the mechanisms underpinning the sigmoid pattern of deoxy[Hb + Mb] during incremental exercise by assessing the changes in the profile following prior high-intensity exercise. Ten physically active students performed two incremental ramp (25 W min) exercises (AL and LL, respectively) preceded on one occasion by incremental arm (10 W min) and on another occasion by incremental leg exercise (25 W min), which served as the reference test (RT). Deoxy[Hb + Mb] was measured by means of near-infrared spectroscopy and surface EMG was recorded at the Vastus Lateralis throughout the exercises. Deoxy[Hb + Mb], integrated EMG and Median Power Frequency (MdPF) were expressed as a function of work rate (W) and compared between the exercises. During RT and AL deoxy[Hb + Mb] followed a sigmoid increase as a function of work rate. However, during LL deoxy[Hb + Mb] increased immediately from the onset of the ramp exercise and thus no longer followed a sigmoid pattern. This different pattern in deoxy[Hb + Mb] was accompanied by a steeper slope of the iEMG/ W-relationship below the GET (LL: 0.89 ± 0.11% W; RT: 0.74 ± 0.08% W; AL: 0.72 ± 0.10% W) and a more pronounced decrease in MdPF in LL (17.2 ± 4.5%) compared to RT (5.0 ± 2.1%) and AL (3.9 ± 3.2%). It was observed that the sigmoid pattern of deoxy[Hb + Mb] was disturbed when the ramp exercise was preceded by priming leg exercise. Since the differences in deoxy[Hb + Mb] were accompanied by differences in EMG it can be suggested that muscle fibre recruitment is an important underlying mechanism for the pattern of deoxy[Hb + Mb] during ramp exercise. [ABSTRACT FROM AUTHOR]

Procurement auctions carry substantial risk when the value of the project is highly uncertain and known only to insiders. This paper reports the results from a series of experiments comparing the performance of three auction formats in such complex and risky settings. In the experiment, every bidder knows the private value for the project but only a single insider bidder knows the common-value part. In addition to the standard second-price and English auctions we test the “qualifying auction,” a two-stage format commonly used in the sale of complex and risky assets. The qualifying auction has a fully “revealing” equilibrium that implements the revenue-maximizing outcome but it also has an uninformative “babbling” equilibrium in which bidders place arbitrarily high bids in the first stage. In the experiments, the latter equilibrium has more drawing power, which causes the qualifying auction to perform worse than the English auction and only slightly better than a sealed-bid second-price auction. Compared to the two other formats, the English auction is roughly 40% more efficient, yields 50% more revenues, avoids windfall profits for the insider, while protecting uninformed bidders from losses. [ABSTRACT FROM AUTHOR]

We present a theoretical analysis of different types of active labor market policies in the context of a search-matching model. We find that labor market training is effective in bringing down unemployment while public employment services and subsidized jobs are not effective at all. This theoretical finding is confirmed in an explorative empirical analysis using data from 20 OECD countries. [ABSTRACT FROM AUTHOR]

During ramp exercise the deoxy[Hb + Mb] pattern follows a sigmoid model [f(x) = f (0) + A/(1 + exp(-(-c +dx))], indicating a non-linear muscle blood flow (Qm)/oxygen uptake (VO25)-relationship. We hypothesised that in trained cyclists the sigmoid would display a rightward shift, due to an increased oxidative capacity and/or higher percentage of slow-twitch fibres. A total of 10 cyclists and 11 physically active students (PA students) performed a relative ramp exercise (+/-12 min) and a ramp25-exercise (25 W min(-1)). Deoxy[Hb + Mb] was measured at the M. Vastus Lateralis by NIRS, normalized to the total amplitude of the response and expressed as a function of absolute and relative (%peakP) work rate. The work rate corresponding to c/d (i.e.50% of the amplitude of the deoxy[Hb + Mb] response) was the only parameter of the sigmoid that differed significantly between cyclists (57.9 +/- 4.4% and 60.1 +/- 4.1%peakP in the relative and ramp25, respectively) and PAstudents (49.6 +/- 4.2% and 48.2 +/- 5.1%peakP, respectively), indicating a rightward shift of the sigmoid in the cyclists. These results suggest a change in the time course of C((a-v))O(2) as a function of aerobic fitness status. [ABSTRACT FROM AUTHOR]

Develops some views on the relationship between competition and innovations. Effect of intensity of competition on total research and development expenditures; Model of technological competition; Questions on the persistence of leadership.

Purpose: The aims of this study were (1) to assess the test–retest reliability of the primary near infrared spectroscopy (NIRS) variables (i.e., StO2, T[Hb], [HbO2] and [HHb]) during cycling and (2) to investigate potential influences of exercise intensity and adipose tissue thickness (ATT) on this reliability.21 men and 20 women completed twelve constant work rate tests (6 min) at six different exercise intensities with each intensity performed twice. NIRS variables were measured at the vastus lateralis. The coefficient of variance (CV%), the intraclass correlation coefficient (ICC), mean bias and limits of agreement (LoA) were determined for reliability purposes.The reliability of baseline values were acceptable to very good (CV% range: 5.83 – 21.96%). The reliability of end-values (CV% range: 0.02 – 25.02%, ICC range: 0.0 – 0.935) and amplitudes (CV% range: 0.46 – 5099%, ICC range: 0.0 – 0.887) were more variable. In general, the mean biases of end-values and amplitudes showed wide limits of agreement. A homogeneous influence of exercise intensity on reliability could not be established but reliability measures appeared to be lower in people with a lower skinfold thickness. Moreover, the NIRS signals decreased with increasing ATT but stabilized upon reaching a cut-off of 8 mm ATT. In addition, ATT did have a significant influence on [HHb] amplitude. In participants with ATT < 8 mm, higher amplitudes were observed with increasing intensity whereas in participants with ATT > 8 mm, there were no differences between the intensities.The study reveals variable results with regards to reliability and there was no consistent influence of exercise intensity on reliability. Participants with a lower skinfold thickness showed stronger reliability. Moreover, NIRS signals decrease when ATT exceeds 8 mm. Careful consideration is necessary when interpreting NIRS signals in such cases.Methods: The aims of this study were (1) to assess the test–retest reliability of the primary near infrared spectroscopy (NIRS) variables (i.e., StO2, T[Hb], [HbO2] and [HHb]) during cycling and (2) to investigate potential influences of exercise intensity and adipose tissue thickness (ATT) on this reliability.21 men and 20 women completed twelve constant work rate tests (6 min) at six different exercise intensities with each intensity performed twice. NIRS variables were measured at the vastus lateralis. The coefficient of variance (CV%), the intraclass correlation coefficient (ICC), mean bias and limits of agreement (LoA) were determined for reliability purposes.The reliability of baseline values were acceptable to very good (CV% range: 5.83 – 21.96%). The reliability of end-values (CV% range: 0.02 – 25.02%, ICC range: 0.0 – 0.935) and amplitudes (CV% range: 0.46 – 5099%, ICC range: 0.0 – 0.887) were more variable. In general, the mean biases of end-values and amplitudes showed wide limits of agreement. A homogeneous influence of exercise intensity on reliability could not be established but reliability measures appeared to be lower in people with a lower skinfold thickness. Moreover, the NIRS signals decreased with increasing ATT but stabilized upon reaching a cut-off of 8 mm ATT. In addition, ATT did have a significant influence on [HHb] amplitude. In participants with ATT < 8 mm, higher amplitudes were observed with increasing intensity whereas in participants with ATT > 8 mm, there were no differences between the intensities.The study reveals variable results with regards to reliability and there was no consistent influence of exercise intensity on reliability. Participants with a lower skinfold thickness showed stronger reliability. Moreover, NIRS signals decrease when ATT exceeds 8 mm. Careful consideration is necessary when interpreting NIRS signals in such cases.Results: The aims of this study were (1) to assess the test–retest reliability of the primary near infrared spectroscopy (NIRS) variables (i.e., StO2, T[Hb], [HbO2] and [HHb]) during cycling and (2) to investigate potential influences of exercise intensity and adipose tissue thickness (ATT) on this reliability.21 men and 20 women completed twelve constant work rate tests (6 min) at six different exercise intensities with each intensity performed twice. NIRS variables were measured at the vastus lateralis. The coefficient of variance (CV%), the intraclass correlation coefficient (ICC), mean bias and limits of agreement (LoA) were determined for reliability purposes.The reliability of baseline values were acceptable to very good (CV% range: 5.83 – 21.96%). The reliability of end-values (CV% range: 0.02 – 25.02%, ICC range: 0.0 – 0.935) and amplitudes (CV% range: 0.46 – 5099%, ICC range: 0.0 – 0.887) were more variable. In general, the mean biases of end-values and amplitudes showed wide limits of agreement. A homogeneous influence of exercise intensity on reliability could not be established but reliability measures appeared to be lower in people with a lower skinfold thickness. Moreover, the NIRS signals decreased with increasing ATT but stabilized upon reaching a cut-off of 8 mm ATT. In addition, ATT did have a significant influence on [HHb] amplitude. In participants with ATT < 8 mm, higher amplitudes were observed with increasing intensity whereas in participants with ATT > 8 mm, there were no differences between the intensities.The study reveals variable results with regards to reliability and there was no consistent influence of exercise intensity on reliability. Participants with a lower skinfold thickness showed stronger reliability. Moreover, NIRS signals decrease when ATT exceeds 8 mm. Careful consideration is necessary when interpreting NIRS signals in such cases.Conclusion: The aims of this study were (1) to assess the test–retest reliability of the primary near infrared spectroscopy (NIRS) variables (i.e., StO2, T[Hb], [HbO2] and [HHb]) during cycling and (2) to investigate potential influences of exercise intensity and adipose tissue thickness (ATT) on this reliability.21 men and 20 women completed twelve constant work rate tests (6 min) at six different exercise intensities with each intensity performed twice. NIRS variables were measured at the vastus lateralis. The coefficient of variance (CV%), the intraclass correlation coefficient (ICC), mean bias and limits of agreement (LoA) were determined for reliability purposes.The reliability of baseline values were acceptable to very good (CV% range: 5.83 – 21.96%). The reliability of end-values (CV% range: 0.02 – 25.02%, ICC range: 0.0 – 0.935) and amplitudes (CV% range: 0.46 – 5099%, ICC range: 0.0 – 0.887) were more variable. In general, the mean biases of end-values and amplitudes showed wide limits of agreement. A homogeneous influence of exercise intensity on reliability could not be established but reliability measures appeared to be lower in people with a lower skinfold thickness. Moreover, the NIRS signals decreased with increasing ATT but stabilized upon reaching a cut-off of 8 mm ATT. In addition, ATT did have a significant influence on [HHb] amplitude. In participants with ATT < 8 mm, higher amplitudes were observed with increasing intensity whereas in participants with ATT > 8 mm, there were no differences between the intensities.The study reveals variable results with regards to reliability and there was no consistent influence of exercise intensity on reliability. Participants with a lower skinfold thickness showed stronger reliability. Moreover, NIRS signals decrease when ATT exceeds 8 mm. Careful consideration is necessary when interpreting NIRS signals in such cases. [ABSTRACT FROM AUTHOR]