Effect of ramp bicycle exercise on exhaled carbon monoxide in humans

The effect of exercise on the increase of exhaled CO in smokers compared to non-smokers has not been clarified yet. In this study we compared the dynamics of exhaled CO before, during and after exercise between smokers and non-smokers. A group of 8 smokers and a group of 8 non-smokers underwent a bicycle exercise in a ramp fashion to near maximum intensity. Ventilation and gas exchange, and CO exhalation were continuously measured every 30-s before, during and after the exercise. The fraction of CO (F _CO) in the exhaled air decreased gradually, but the total amount of exhaled CO ([(V)\dot]_\textCO ) (\dot{V}_{{{\text{CO}}}} ) increased in a linear manner during the ramp exercise, and F _CO and [(V)\dot]_\textCO \dot{V}_{\text{CO}} returned to the pre-exercise level within several minutes after exercise in all subjects. A linear relationship was observed between [(V)\dot]_{\textO 2} \dot{V}_{{{\text{O}}_{ 2} }} and [(V)\dot]_\textCO , \dot{V}_{\text{CO}} , and between [(V)\dot]_\textE \dot{V}_{\text{E}} and [(V)\dot]_\textCO \dot{V}_{\text{CO}} in both the whole period of measurement and during the ramp exercise period in all subjects. However, the [(V)\dot]_\textCO \dot{V}_{\text{CO}} at 0 W, the peak [(V)\dot]_\textCO \dot{V}_{\text{CO}} and the slope coefficients in the regression equation between [(V)\dot]_\textCO \dot{V}_{\text{CO}} and [(V)\dot]_{\textO 2} , \dot{V}_{{{\text{O}}_{ 2} }} , and between [(V)\dot]_\textCO \dot{V}_{\text{CO}} and [(V)\dot]_\textE \dot{V}_{\text{E}} in the ramp exercise as well as the entire periods of measurement were significantly higher in smokers compared with those in non-smokers, and these were correlated with the number of cigarettes smoked per day. It was concluded that CO exhalation increases linearly with the increase of [(V)\dot]_{\textO 2} \dot{V}_{{{\text{O}}_{ 2} }} and [(V)\dot]_\textE \dot{V}_{\text{E}} during exercise, and habitual smoking shifts these relationships upward depending on the number of cigarettes smoked daily.     

Estimates of ventilation from measurements of rib cage and abdominal distances: a portable device

To validate a new device designed to measure ventilation ( [(V)\dot]_\textE ), \left( {\dot{V}_{\text{E}} } \right), tidal volume (V _T), inspiratory time (T _I), and expiratory time (T _E) during daily life activities. The anteroposterior displacement of the rib cage and abdomen and the axial displacements of the chest wall and the spine were measured using two pairs of magnetometers. [(V)\dot]_\textE \dot{V}_{\text{E}} was estimated from these four signals, and was simultaneously measured using a spirometer. A total of 707, 732, and 1,138 breaths were analyzed in sitting, standing, and exercise conditions, respectively. We compared [(V)\dot]_\textE \dot{V}_{\text{E}} , V _T, T _I, and, T _E measured by magnetometers ( [(V)\dot]_{\textE  \textmag} \dot{V}_{{{\text{E}}\;{\text{mag}}}} , V _{T mag}, T _{I mag}, and T _{E mag}) with [(V)\dot]_\textE \dot{V}_{\text{E}} , V _T, T _I, and T _E measured by a spirometer ( [(V)\dot]_{\textE  \textspiro} \dot{V}_{{{\text{E}}\;{\text{spiro}}}} , V _{T spiro}, T _{I spiro}, and T _{E spiro}, respectively). For pooled data [(V)\dot]_{\textE  \textmag} \dot{V}_{{{\text{E}}\;{\text{mag}}}} , V _{T mag}, T _{I mag}, and T _{E mag} were significantly correlated (p < 0.001) with [(V)\dot]_{\textE  \textspiro} \dot{V}_{{{\text{E}}\;{\text{spiro}}}} , V _{T spiro}, T _{I spiro}, and T _{E spiro} in sitting and standing positions and during the walking exercise. The mean differences, between [(V)\dot]_{\textE  \textmag} \dot{V}_{{{\text{E}}\;{\text{mag}}}} , and [(V)\dot]_{\textE  \textspiro} \dot{V}_{{{\text{E}}\;{\text{spiro}}}} for the group, were 10.44, 10.74, and 12.06% in sitting, standing, and exercise conditions, respectively. These results demonstrate the capacity of this new device to measure [(V)\dot]_\textE \dot{V}_{\text{E}} with reasonable accuracy in sitting, standing, and exercise conditions.     

Short-term exercise-heat acclimation enhances skin vasodilation but not hyperthermic hyperpnea in humans exercising in a hot environment

We tested the hypothesis that short-term exercise-heat acclimation (EHA) attenuates hyperthermia-induced hyperventilation in humans exercising in a hot environment. Twenty-one male subjects were divided into the two groups: control (C, n = 11) and EHA (n = 10). Subjects in C performed exercise-heat tests [cycle exercise for ~75 min at 58% [(V)\dot]_{\textO 2 \textpeak} \dot{V}_{{{\text{O}}_{{ 2 {\text{peak}}}} }} (37°C, 50% relative humidity)] before and after a 6-day interval with no training, while subjects in EHA performed the tests before and after exercise training in a hot environment (37°C). The training entailed four 20-min bouts of exercise at 50% [(V)\dot]_{\textO 2 \textpeak} \dot{V}_{{{\text{O}}_{{ 2 {\text{peak}}}} }} separated by 10 min of rest daily for 6 days. In C, comparison of the variables recorded before and after the no-training period revealed no changes. In EHA, the training increased resting plasma volume, while it reduced esophageal temperature (T _es), heart rate at rest and during exercise, and arterial blood pressure and oxygen uptake ( [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} ) during exercise. The training lowered the T _es threshold for increasing forearm vascular conductance (FVC), while it increased the slope relating FVC to T _es and the peak FVC during exercise. It also lowered minute ventilation ( [(V)\dot]_\textE \dot{V}_{\text{E}} ) during exercise, but this effect disappeared after removing the influence of [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} on [(V)\dot]_\textE \dot{V}_{\text{E}} . The training did not change the slope relating ventilatory variables to T _es. We conclude that short-term EHA lowers ventilation largely by reducing metabolism, but it does not affect the sensitivity of hyperthermia-induced hyperventilation during submaximal, moderate-intensity exercise in humans.     

Prediction of peak oxygen uptake from age and power output at RPE 15 in obese women

The purpose of this study was to develop a simple, convenient and indirect method for predicting peak oxygen uptake ( [(V)\dot]\textO_2\textpeak \dot{V}{\text{O}}_{{2{\text{peak}}}} ) from a sub-maximal graded exercise test (GXT), in obese women. Thirty obese women performed GXT to volitional exhaustion. During GXT, oxygen uptake and the power at RPE 15 ( P_{\textRPE  15} P_{{{\text{RPE}}\;15}} ) were measured, and [(V)\dot]\textO_2\textpeak \dot{V}{\text{O}}_{{2{\text{peak}}}} was determined. Following assessment of the relationships between [(V)\dot]\textO_2\textpeak \dot{V}{\text{O}}_{{2{\text{peak}}}} and P_{\textRPE  15} P_{{{\text{RPE}}\;15}} , age, height and mass were made available in a stepwise multiple regression analysis with [(V)\dot]\textO_2\textpeak \dot{V}{\text{O}}_{{2{\text{peak}}}} as the dependent variable. The equation to predict [(V)\dot]\textO_2\textpeak \dot{V}{\text{O}}_{{2{\text{peak}}}} was:

Evaluation of the Oxycon Mobile metabolic system against the Douglas bag method

The aim of this study was to evaluate two versions of the Oxycon Mobile portable metabolic system (OMPS1 and OMPS2) in a wide range of oxygen uptake, using the Douglas bag method (DBM) as criterion method. The metabolic variables [(V)\dot]\textO₂ , [(V)\dot]\textCO₂ , \dot{V}{\text{O}}_{2} , \dot{V}{\text{CO}}_{2} , respiratory exchange ratio and [(V)\dot]_\textE \dot{V}_{\text{E}} were measured during submaximal and maximal cycle ergometer exercise with sedentary, moderately trained individuals and athletes as participants. Test–retest reliability was investigated using the OMPS1. The coefficients of variation varied between 2 and 7% for the metabolic parameters measured at different work rates and resembled those obtained with the DBM. With the OMPS1, systematic errors were found in the determination of [(V)\dot]\textO₂ \dot{V}{\text{O}}_{2} and [(V)\dot]\textCO₂ . \dot{V}{\text{CO}}_{2} . At submaximal work rates [(V)\dot]\textO₂ \dot{V}{\text{O}}_{2} was 6–14% and [(V)\dot]\textCO₂ \dot{V}{\text{CO}}_{2} 5–9% higher than with the DBM. At [(V)\dot]\textO_2max \dot{V}{\text{O}}_{2\max } both [(V)\dot]\textO₂ \dot{V}{\text{O}}_{2} and [(V)\dot]\textCO₂ \dot{V}{\text{CO}}_{2} were slightly lower as compared to DBM (−4.1 and −2.8% respectively). With OMPS2, [(V)\dot]\textO₂ \dot{V}{\text{O}}_{2} was determined accurately within a wide measurement range (about 1–5.5 L min⁻¹), while [(V)\dot]\textCO₂ \dot{V}{\text{CO}}_{2} was overestimated (3–7%). [(V)\dot]_\textE \dot{V}_{\text{E}} was accurate at submaximal work rates with both OMPS1 and OMPS2, whereas underestimations (4–8%) were noted at [(V)\dot]\textO_2max . \dot{V}{\text{O}}_{2\max } . The present study is the first to demonstrate that a wide range of [(V)\dot]\textO₂ \dot{V}{\text{O}}_{2} can be measured accurately with the Oxycon Mobile portable metabolic system (second generation). Future investigations are suggested to clarify reasons for the small errors noted for [(V)\dot]_\textE \dot{V}_{\text{E}} and [(V)\dot]\textCO₂ \dot{V}{\text{CO}}_{2} versus the Douglas bag measurements, and also to gain knowledge of the performance of the device under applied and non-laboratory conditions.     

An examination of exercise mode on ventilatory patterns during incremental exercise

Both cycle ergometry and treadmill exercise are commonly employed to examine the cardiopulmonary system under conditions of precisely controlled metabolic stress. Although both forms of exercise are effective in elucidating a maximal stress response, it is unclear whether breathing strategies or ventilator efficiency differences exist between exercise modes. The present study examines breathing strategies, ventilatory efficiency and ventilatory capacity during both incremental cycling and treadmill exercise to volitional exhaustion. Subjects (n = 9) underwent standard spirometric assessment followed by maximal cardiopulmonary exercise testing utilising cycle ergometry and treadmill exercise using a randomised cross-over design. Respiratory gases and volumes were recorded continuously using an online gas analysis system. Cycling exercise utilised a greater portion of ventilatory capacity and higher tidal volume at comparable levels of ventilation. In addition, there was an increased mean inspiratory flow rate at all levels of ventilation during cycle exercise, in the absence of any difference in inspiratory timing. Exercising [(V)\dot]_\textE / [(V)\dot]\textCO₂ {{\dot{V}_{\text{E}} }/ {\dot{V}{\text{CO}}_{2} }} slope and the lowest [(V)\dot]_\textE / [(V)\dot]\textCO₂ {{\dot{V}_{\text{E}} }/ {\dot{V}{\text{CO}}_{2} }} value, was lower during cycling exercise than during the treadmill protocol indicating greater ventilatory efficiency. The present study identifies differing breathing strategies employed during cycling and treadmill exercise in young, trained individuals. Exercise mode should be accounted for when assessing breathing patterns and/or ventilatory efficiency during incremental exercise.     

Assessment of the effects of physical training in patients with chronic heart failure: the utility of effort-independent exercise variables

Traditionally, the effects of physical training in patients with chronic heart failure (CHF) are evaluated by changes in peak oxygen uptake (peak [(V)\dot]\textO₂ \dot{V}{\text{O}}_{2} ). The assessment of peak [(V)\dot]\textO₂ \dot{V}{\text{O}}_{2} , however, is highly dependent on the patients’ motivation. The aim of the present study was to evaluate the clinical utility of effort-independent exercise variables for detecting training effects in CHF patients. In a prospective controlled trial, patients with stable CHF were allocated to an intervention group (N = 30), performing a 12-week combined cycle interval and muscle resistance training program, or a control group (N = 18) that was matched for age, gender, body composition and left ventricular ejection fraction. The following effort-independent exercise variables were evaluated: the ventilatory anaerobic threshold (VAT), oxygen uptake efficiency slope (OUES), the [(V)\dot]_\textE /[(V)\dot]\textCO ₂ \dot{V}_{\text{E}} /\dot{V}{\text{CO}}_{ 2} slope and the time constant of [(V)\dot]\textO₂ \dot{V}{\text{O}}_{2} kinetics during recovery from submaximal constant-load exercise (τ-rec). In addition to post-training increases in peak [(V)\dot]\textO₂ \dot{V}{\text{O}}_{2} and peak [(V)\dot]_\textE , \dot{V}_{\text{E}} , , the intervention group showed significant within and between-group improvements in VAT, OUES and τ-rec. There were no significant differences between relative improvements of the effort-independent exercise variables in the intervention group. In contrast with VAT, which could not be determined in 9% of the patients, OUES and τ-rec were determined successfully in all patients. Therefore, we conclude that OUES and τ-rec are useful in clinical practice for the assessment of training effects in CHF patients, especially in cases of poor subject effort during symptom-limited exercise testing or when patients are unable to reach a maximal exercise level.     

Physiological and perceptual responses to Nordic walking in obese middle-aged women in comparison with the normal walk

This study aimed to compare physiological and perceptual responses to Nordic walking (NW) in obese women to those of walking (W), and to assess if these responses were modified by a learning period of NW technique. Eleven middle-aged obese women completed exercise trials (5 min each) at 4 km/h, inclinations of −5, 0 and +5%, with and without poles. Ventilation ( \mathop V^._\textE ), \left( {\mathop V\limits^{.}}_{\text{E} } \right), oxygen consumption ([(V)\dot]_\textO\text2)(\dot{V}_{{{\text{O}}_{{\text{2}}}}}) energy cost (EC), heart rate (HR), rating of perceived exertion (RPE) and cycle length were measured before and after a 4-week learning period (12 sessions). \mathop V^._\textE ,[(V)\dot]_\textO\text2 , {\mathop V\limits^{.}}_{\text{E} } ,\dot{V}_{{{\text{O}}_{{\text{2}}}}} , EC, HR and cycle length were significantly higher (P < 0.001) during NW trials than W trials. RPE was significantly diminished (pole × inclination interaction, P = 0.031) when using NW poles compared to W uphill. Significant pole × inclination interactions were observed for [(V)\dot]_\textO\text2 \dot{V}_{{{\text{O}}_{{\text{2}}}}} (P = 0.022) and EC (P = 0.022), whereas significant pole × time interaction was found for EC (P = 0.043) and RPE (P = 0.039). Our results confirmed that use of NW poles increased physiological responses at a given speed but decreased RPE in comparison with W during inclined level. Moreover, this is the first study showing that a learning period of NW technique permitted to enhance the difference between EC with NW poles versus the W condition and to decrease the RPE when using NW poles. Thus, although it requires a specific learning of the technique, the NW might be considered like an attractive physical activity with an important public health application.     

Inter-individual variability in adaptation of the leg muscles following a standardised endurance training programme in young women

There is considerable inter-individual variability in adaptations to endurance training. We hypothesised that those individuals with a low local leg-muscle peak aerobic capacity ([(V)\dot] \textO_2\textpeak) (\dot{V} {\text{O}}_{{2{\text{peak}}}}) relative to their whole-body maximal aerobic capacity ( [(V)\dot] \textO_2max) ( \dot{V} {\text{O}}_{2\max}) would experience greater muscle training adaptations compared to those with a relatively high [(V)\dot] \textO_2\textpeak \dot{V} {\text{O}}_{{2{\text{peak}}}} . 53 untrained young women completed one-leg cycling to measure [(V)\dot] \textO_2\textpeak \dot{V} {\text{O}}_{{2{\text{peak}}}} and two-leg cycling to measure [(V)\dot] \textO_2max \dot{V} {\text{O}}_{2\max} . The one-leg [(V)\dot] \textO_2\textpeak \dot{V} {\text{O}}_{{2{\text{peak}}}} was expressed as a ratio of the two-leg [(V)\dot] \textO_2max \dot{V} {\text{O}}_{2\max} (Ratio _1:2). Magnetic resonance imaging was used to indicate quadriceps muscle volume. Measurements were taken before and after completion of 6 weeks of supervised endurance training. There was large inter-individual variability in the pre-training Ratio _1:2 and large variability in the magnitude of training adaptations. The pre-training Ratio _1:2 was not related to training-induced changes in [(V)\dot] \textO_2max \dot{V} {\text{O}}_{2\max} (P = 0.441) but was inversely correlated with changes in one-leg [(V)\dot] \textO_2\textpeak \dot{V} {\text{O}}_{{2{\text{peak}}}} and muscle volume (P < 0.05). No relationship was found between the training-induced changes in two-leg [(V)\dot] \textO_2max \dot{V} {\text{O}}_{2\max} and one-leg [(V)\dot] \textO_2\textpeak \dot{V} {\text{O}}_{{2{\text{peak}}}} (r = 0.21; P = 0.129). It is concluded that the local leg-muscle aerobic capacity and Ratio _1:2 vary from person to person and this influences the extent of muscle adaptations following standardised endurance training. These results help to explain why muscle adaptations vary between people and suggest that setting the training stimulus at a fixed percentage of [(V)\dot] \textO_2max \dot{V} {\text{O}}_{2\max} might not be a good way to standardise the training stimulus to the leg muscles of different people.     

Impact of Airway Gas Exchange on the Multiple Inert Gas Elimination Technique: Theory

The multiple inert gas elimination technique (MIGET) provides a method for estimating alveolar gas exchange efficiency. Six soluble inert gases are infused into a peripheral vein. Measurements of these gases in breath, arterial blood, and venous blood are interpreted using a mathematical model of alveolar gas exchange (MIGET model) that neglects airway gas exchange. A mathematical model describing airway and alveolar gas exchange predicts that two of these gases, ether and acetone, exchange primarily within the airways. To determine the effect of airway gas exchange on the MIGET, we selected two additional gases, toluene and m-dichlorobenzene, that have the same blood solubility as ether and acetone and minimize airway gas exchange via their low water solubility. The airway-alveolar gas exchange model simulated the exchange of toluene, m-dichlorobenzene, and the six MIGET gases under multiple conditions of alveolar ventilation-to-perfusion, [(V)\dot]_\textA /[(Q)\dot] \dot{V}_{\text{A}} /\dot{Q} , heterogeneity. We increased the importance of airway gas exchange by changing bronchial blood flow, [(Q)\dot]_\textbr \dot{Q}_{\text{br}} . From these simulations, we calculated the excretion and retention of the eight inert gases and divided the results into two groups: (1) the standard MIGET gases which included acetone and ether and (2) the modified MIGET gases which included toluene and m-dichlorobenzene. The MIGET mathematical model predicted distributions of ventilation and perfusion for each grouping of gases and multiple perturbations of [(V)\dot]_\textA /[(Q)\dot] \dot{V}_{\text{A}} /\dot{Q} and [(Q)\dot]_\textbr \dot{Q}_{\text{br}} . Using the modified MIGET gases, MIGET predicted a smaller dead space fraction, greater mean [(V)\dot]_\textA \dot{V}_{\text{A}} , greater log(SD_VA), and more closely matched the imposed [(V)\dot]_\textA \dot{V}_{\text{A}} distribution than that using the standard MIGET gases. Perfusion distributions were relatively unaffected.     

Oxygen uptake and blood metabolic responses to a 400-m run

This study aimed to investigate the oxygen uptake and metabolic responses during a 400-m run reproducing the pacing strategy used in competition. A portable gas analyser was used to measure the oxygen uptake ( [(V)\dot]\textO ₂ ) \left( {\dot{V}{{{\text{O}}_{ 2} }} } \right) of ten specifically trained runners racing on an outdoor track. The tests included (1) an incremental test to determine maximal [(V)\dot]\textO ₂  ( [(V)\dot]\textO _{2 \textmax} ) \dot{V}{{{\text{O}}_{ 2} }} \,\left( {\dot{V}{{{\text{O}}_{{ 2 {\text{max}}}} }} } \right) and the velocity associated with [(V)\dot]\textO _{2 \textmax} ( \textv-[(V)\dot]\textO _{2 \textmax} ), \dot{V}{{{\text{O}}_{{ 2 {\text{max}}}} }} \left( {{\text{v}}-\dot{V}{{{\text{O}}_{{ 2 {\text{max}}}} }} } \right), (2) a maximal 400-m (400T) and 3) a 300-m running test (300T) reproducing the exact pacing pattern of the 400T. Blood lactate, bicarbonate concentrations [ \textHCO ₃ ^- ], \left[ {{\text{HCO}}_{ 3}^{ - } } \right], pH and arterial oxygen saturation were analysed at rest and 1, 4, 7, 10 min after the end of the 400 and 300T. The peak [(V)\dot]\textO ₂ \dot{V}{{{\text{O}}_{ 2} }} recorded during the 400T corresponded to 93.9 ± 3.9% of [(V)\dot]\textO_2max \dot{V}{{{\text{O}}_{2\max } }} and was reached at 24.4 ± 3.2 s (192 ± 22 m). A significant decrease in [(V)\dot]\textO ₂ \dot{V}{{{\text{O}}_{ 2} }} (P < 0.05) was observed in all subjects during the last 100 m, although the velocity did not decrease below \textv-[(V)\dot]_{\textO 2 \textmax} . {\text{v}}-\dot{V}_{{{\text{O}}_{{ 2 {\text{max}}}} }} . The [(V)\dot]\textO ₂ \dot{V}{{{\text{O}}_{ 2} }} in the last 5 s was correlated with the pH (r = 0.86, P < 0.0005) and [ \textHCO ₃ ^- ] \left[ {{\text{HCO}}_{ 3}^{ - } } \right] (r = 0.70, P < 0.05) measured at the end of 300T. Additionally, the velocity decrease observed in the last 100 m was inversely correlated with [ \textHCO ₃ ^- ] \left[ {{\text{HCO}}_{ 3}^{ - } } \right] and pH at 300T (r = −0.83, P < 0.001, r = −0.69, P < 0.05, respectively). These track running data demonstrate that acidosis at 300 m was related to both the [(V)\dot]\textO ₂ \dot{V}{{{\text{O}}_{ 2} }} response and the velocity decrease during the final 100 m of a 400-m run.     

Performance and physiological responses during a sprint interval training session: relationships with muscle oxygenation and pulmonary oxygen uptake kinetics

The purpose of this study was to examine the cardiorespiratory and muscle oxygenation responses to a sprint interval training (SIT) session, and to assess their relationships with maximal pulmonary O₂ uptake ([(V)\dot]\textO _{2 \textp} \textmax) (\dot{V}{\text{O}}_{{ 2 {\text{p}}}} {\text{max)}} , on- and off- [(V)\dot]\textO _{2 \textp} \dot{V}{\text{O}}_{{ 2 {\text{p}}}} kinetics and muscle reoxygenation rate (Reoxy rate). Ten male cyclists performed two 6-min moderate-intensity exercises (≈90–95% of lactate threshold power output, Mod), followed 10 min later by a SIT session consisting of 6 × 30-s all out cycling sprints interspersed with 2 min of passive recovery. [(V)\dot]\textO _{2 \textp} \dot{V}{\text{O}}_{{ 2 {\text{p}}}} kinetics at Mod onset ( [(V)\dot]\textO _{2 \textp} t_\texton \dot{V}{\text{O}}_{{ 2 {\text{p}}}} \tau_{\text{on}} ) and cessation ( [(V)\dot]\textO _{2 \textp} t_\textoff \dot{V}{\text{O}}_{{ 2 {\text{p}}}} \tau_{\text{off}} ) were calculated. Cardiorespiratory variables, blood lactate ([La]_b) and muscle oxygenation level of the vastus lateralis (tissue oxygenation index, TOI) were recorded during SIT. Percentage of the decline in power output (%Dec), time spent above 90% of [(V)\dot]\textO _{2 \textp} max \dot{V}{\text{O}}_{{ 2 {\text{p}}}} { \max } (t > 90% [(V)\dot]\textO _{2 \textp} max \dot{V}{\text{O}}_{{ 2 {\text{p}}}} { \max } ) and Reoxy rate after each sprint were also recorded. Despite a low mean [(V)\dot]\textO _{2 \textp} \dot{V}{\text{O}}_{{ 2 {\text{p}}}} (48.0 ± 4.1% of [(V)\dot]\textO _{2 \textp} max \dot{V}{\text{O}}_{{ 2 {\text{p}}}} { \max } ), SIT performance was associated with high peak [(V)\dot]\textO _{2 \textp} \dot{V}{\text{O}}_{{ 2 {\text{p}}}} (90.4 ± 2.8% of [(V)\dot]\textO _{2 \textp} max \dot{V}{\text{O}}_{{ 2 {\text{p}}}} { \max } ), muscle deoxygenation (sprint ΔTOI = −27%) and [La]_b (15.3 ± 0.7 mmol l⁻¹) levels. Muscle deoxygenation and Reoxy rate increased throughout sprint repetitions (P < 0.001 for both). Except for t > 90% [(V)\dot]\textO _{2 \textp} max \dot{V}{\text{O}}_{{ 2 {\text{p}}}} { \max } versus [(V)\dot]\textO _{2 \textp} t_\textoff \dot{V}{\text{O}}_{{ 2 {\text{p}}}} \tau_{\text{off}} [r = 0.68 (90% CL, 0.20; 0.90); P = 0.03], there were no significant correlations between any index of aerobic function and either SIT performance or physiological responses [e.g., %Dec vs. [(V)\dot]\textO _{2 \textp} t_\textoff \dot{V}{\text{O}}_{{ 2 {\text{p}}}} \tau_{\text{off}} : r = −0.41 (−0.78; 0.18); P = 0.24]. Present results show that SIT elicits a greater muscle O₂ extraction with successive sprint repetitions, despite the decrease in external power production (%Dec = 21%). Further, our findings obtained in a small and homogenous group indicate that performance and physiological responses to SIT are only slightly influenced by aerobic fitness level in this population.     

Group- and individual-level coincidence of the ‘Fatmax’ and lactate accumulation in adolescents

Fatmax and lactate increase above baseline (LIAB) were measured in 11 adolescent girls and 8 adolescent boys during incremental cycling. Fatmax was the exercise intensity at the point of maximal fat oxidation rate (MFO). The LIAB was the exercise intensity coincident with a sustained increase in blood (lactate) above an initial baseline. We defined the minimum important difference (MID) between the exercise intensity at Fatmax and LIAB as ±8% of both peak [(V)\dot]\textO₂ {\dot{V}}{\text{O}}_{2} and peak heart rate (HR). Systematic bias was examined via the mean difference between parameters and its uncertainty, with inference based on the disposition of the confidence interval to the MID. Individual-level agreement was the proportion of differences between Fatmax and LIAB falling within the MID. MFO was at 35 (6)% peak [(V)\dot]\textO₂ {\dot{V}}{\text{O}}_{2} with LIAB at 39 (7)% peak [(V)\dot]\textO₂. {\dot{V}}{\text{O}}_{2}. Systematic bias was −3.8% of peak [(V)\dot]\textO₂ {\dot{V}}{\text{O}}_{2} and −4.4% of peak HR. The estimated population proportion with between-variable agreement within ±8% was 0.76 for both % peak [(V)\dot]\textO₂ {\dot{V}}{\text{O}}_{2} and % peak HR. Within the tolerance limits of the MID, the mean bias is ‘almost certainly not’ important; similarly, there is good agreement between the two parameters at the individual level. We conclude that Fatmax and lactate increase above baseline coincide in adolescents.     

Energetics of karate (<Emphasis Type="Italic">kata</Emphasis> and <Emphasis Type="Italic">kumite</Emphasis> techniques) in top-level athletes

Breath-by-breath O₂ uptake ( [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} , L min⁻¹) and blood lactate concentration were measured before, during exercise, and recovery in six kata and six kumite karate Word Champions performing a simulated competition. [(V)\dot]_{\textO 2 \textmax} , \dot{V}_{{{\text{O}}_{{ 2 {\text{max}}}} }} , maximal anaerobic alactic, and lactic power were also assessed. The total energy cost ( V_{\textO 2 \textTOT} , V_{{{\text{O}}_{{ 2 {\text{TOT}}}} }} , mL kg⁻¹ above resting) of each simulated competition was calculated and subdivided into aerobic, lactic, and alactic fractions. Results showed that (a) no differences between kata and kumite groups in [(V)\dot]_{\textO 2 \textmax} , \dot{V}_{{{\text{O}}_{{ 2 {\text{max}}}} }} , height of vertical jump, and Wingate test were found; (b) V_{\textO 2 \textTOT} V_{{{\text{O}}_{{ 2 {\text{TOT}}}} }} were 87.8 ± 6.6 and 82.3 ± 12.3 mL kg⁻¹ in kata male and female with a performance time of 138 ± 4 and 158 ± 14 s, respectively; 189.0 ± 14.6 mL kg⁻¹ in kumite male and 155.8 ± 38.4 mL kg⁻¹ in kumite female with a predetermined performance time of 240 ± 0 and 180 ± 0 s, respectively; (c) the metabolic power was significantly higher in kumite than in kata athletes (p ≤ 0.05 in both gender); (d) aerobic and anaerobic alactic sources, in percentage of the total, were significantly different between gender and disciplines (p < 0.05), while the lactic source was similar; (e) HR ranged between 174 and 187 b min⁻¹ during simulated competition. In conclusion, kumite appears to require a much higher metabolic power than kata, being the energy source with the aerobic contribution predominant.     

Prediction of maximal oxygen uptake from submaximal ratings of perceived exertion and heart rate during a continuous exercise test: the efficacy of RPE 13

This study assessed the utility of a single, continuous exercise protocol in facilitating accurate estimates of maximal oxygen uptake ( [(V)\dot] \textO ₂ \dot{V} {\text{O}}_{ 2} max) from submaximal heart rate (HR) and the ratings of perceived exertion (RPE) in healthy, low-fit women, during cycle ergometry. Eleven women estimated their RPE during a continuous test (1 W 4 s⁻¹) to volitional exhaustion (measured [(V)\dot] \textO ₂ \dot{V} {\text{O}}_{ 2} max). Individual gaseous exchange thresholds (GETs) were determined retrospectively. The RPE and HR values prior to and including an RPE 13 and GET were extrapolated against corresponding oxygen uptake to a theoretical maximal RPE (20) and peak RPE (19), and age-predicted HRmax, respectively, to predict [(V)\dot] \textO ₂ \dot{V} {\text{O}}_{ 2} max. There were no significant differences (P > 0.05) between measured (30.9 ± 6.5 ml kg⁻¹ min⁻¹) and predicted [(V)\dot] \textO ₂ \dot{V} {\text{O}}_{ 2} max from all six methods. Limits of agreement were narrowest and intraclass correlations were highest for predictions of [(V)\dot] \textO ₂ \dot{V} {\text{O}}_{ 2} max from an RPE 13 to peak RPE (19). Prediction of [(V)\dot] \textO ₂ \dot{V} {\text{O}}_{ 2} max from a regression equation using submaximal HR and work rate at an RPE 13 was also not significantly different to actual [(V)\dot] \textO ₂ \dot{V} {\text{O}}_{ 2} max (R ²  = 0.78, SEE = 3.42 ml kg⁻¹ min⁻¹, P > 0.05). Accurate predictions of [(V)\dot] \textO ₂ \dot{V} {\text{O}}_{ 2} max may be obtained from a single, continuous, estimation exercise test to a moderate intensity (RPE 13) in low-fit women, particularly when extrapolated to peak terminal RPE (RPE₁₉). The RPE is a valuable tool that can be easily employed as an adjunct to HR, and provides supplementary clinical information that is superior to using HR alone.     

Critical power in adolescents: physiological bases and assessment using all-out exercise

This study examined whether critical power (CP) in adolescents: (1) provides a landmark for maximal steady-state exercise; and (2) can be determined using ‘all-out’ exercise. Nine active 14–15 year olds (6 females, 3 males) performed five cycling tests: (1) a ramp test to determine [(V)\dot]\textO_2 \textpeak \dot{V}{\text{O}}_{{2\,{\text{peak}}}} ; (2) up to four constant power output tests to determine CP; (3–4) constant power output exercise 10% above and 10% below CP; and (5) a 3 min all-out cycle test to establish the end power (EP) at 90 and 180 s of exercise. All participants completed 30 min of exercise below CP and were characterized by steady-state blood lactate and [(V)\dot]\textO₂ {\dot{V}\text{O}}_{2} profiles. In contrast, time to exhaustion during exercise above CP was 15.0 ± 7.0 min and characterized by an inexorable rise in blood lactate and a rise, stabilization (~91% [(V)\dot]\textO_2 \textpeak {\dot{V}\text{O}}_{{2\,{\text{peak}}}} ) and fall in [(V)\dot]\textO₂ {\dot{V}\text{O}}_{2} (~82% [(V)\dot]\textO_2 \textpeak {\dot{V}\text{O}}_{{2\,{\text{peak}}}} ) prior to exhaustion. Eight out of nine participants completed the 3 min test and their EPs at 90 s (148 ± 29 W) and 180 s (146 ± 30 W) were not different from CP (146 ± 27 W) (P = 0.98). The typical error of estimates for establishing CP using EP at 90 s or 180 s of the 3 min test were 25 W (19.7% CV) and 25 W (19.6% CV), respectively. CP in active adolescence provides a valid landmark for maximal steady-state exercise, although its estimation on an individual level using the 3 min all-out test may be of limited value.     

Physiological determinants of Yo-Yo intermittent recovery tests in male soccer players

The physiological determinants of performance in two Yo-Yo intermittent recovery tests (Yo-YoIR1 and Yo-YoIR2) were examined in 25 professional (n = 13) and amateur (n = 12) soccer players. The aims of the study were (1) to examine the differences in physiological responses to Yo-YoIR1 and Yo-YoIR2, (2) to determine the relationship between the aerobic and physiological responses to standardized high-intensity intermittent exercise (HIT) and Yo-Yo performance, and (3) to investigate the differences between professional and amateur players in performance and responses to these tests. All players performed six tests: two versions of the Yo-Yo tests, a test for the determination of maximum oxygen uptake ( [(\textV)\dot]\textO_{2  max} {\dot{\text{V}}}{\text{O}}_{{2\,{ \max }}} ), a double test to determine [(\textV)\dot]\textO₂ {\dot{\text{V}}}{\text{O}}_{2} kinetics and a HIT evaluation during which several physiological responses were measured. The anaerobic contribution was greatest during Yo-YoIR2. [(\textV)\dot]\textO_{2  max} {\dot{\text{V}}}{\text{O}}_{{2\,{ \max }}} was strongly correlated with Yo-YoIR1 (r = 0.74) but only moderately related to Yo-YoIR2 (r = 0.47). The time constant (τ) of [(\textV)\dot]\textO₂ {\dot{\text{V}}}{\text{O}}_{2} kinetics was largely related to both Yo-Yo tests (Yo-YoIR1: r = 0.60 and Yo-YoIR2: r = 0.65). The relationships between physiological variables measured during HIT (blood La⁻, H⁺, HCO₃ ⁻ and the rate of La⁻ accumulation) and Yo-Yo performance (in both versions) were very large (r > 0.70). The physiological responses to HIT and the τ of the [(\textV)\dot]\textO₂ {\dot{\text{V}}}{\text{O}}_{2} kinetics were significantly different between professional and amateur soccer players, whilst [(\textV)\dot]\textO_{2  max} {\dot{\text{V}}}{\text{O}}_{{2\,{ \max }}} was not significantly different between the two groups. In conclusion, [(\textV)\dot]\textO_{2  max} {\dot{\text{V}}}{\text{O}}_{{2\,{ \max }}} is more important for Yo-YoIR1 performance, whilst τ of the [(\textV)\dot]\textO₂ {\dot{\text{V}}}{\text{O}}_{2} kinetics and the ability to maintain acid–base balance are important physiological factors for both Yo-Yo tests.     

Pulmonary oxygen uptake and muscle deoxygenation kinetics during recovery in trained and untrained male adolescents

Previous studies have demonstrated faster pulmonary oxygen uptake ( [(V)\dot]\textO₂ \dot{V}{\text{O}}_{2} ) kinetics in the trained state during the transition to and from moderate-intensity exercise in adults. Whilst a similar effect of training status has previously been observed during the on-transition in adolescents, whether this is also observed during recovery from exercise is presently unknown. The aim of the present study was therefore to examine [(V)\dot]\textO₂ \dot{V}{\text{O}}_{2} kinetics in trained and untrained male adolescents during recovery from moderate-intensity exercise. 15 trained (15 ± 0.8 years, [(V)\dot]\textO_2max \dot{V}{\text{O}}_{2\max} 54.9 ± 6.4 mL kg⁻¹ min⁻¹) and 8 untrained (15 ± 0.5 years, [(V)\dot]\textO_2max \dot{V}{\text{O}}_{2\max } 44.0 ± 4.6 mL kg⁻¹ min⁻¹) male adolescents performed two 6-min exercise off-transitions to 10 W from a preceding “baseline” of exercise at a workload equivalent to 80% lactate threshold; [(V)\dot]\textO₂ \dot{V}{\text{O}}_{2} (breath-by-breath) and muscle deoxyhaemoglobin (near-infrared spectroscopy) were measured continuously. The time constant of the fundamental phase of [(V)\dot]\textO₂ \dot{V}{\text{O}}_{2} off-kinetics was not different between trained and untrained (trained 27.8 ± 5.9 s vs. untrained 28.9 ± 7.6 s, P = 0.71). However, the time constant (trained 17.0 ± 7.5 s vs. untrained 32 ± 11 s, P < 0.01) and mean response time (trained 24.2 ± 9.2 s vs. untrained 34 ± 13 s, P = 0.05) of muscle deoxyhaemoglobin off-kinetics was faster in the trained subjects compared to the untrained subjects. [(V)\dot]\textO₂ \dot{V}{\text{O}}_{2} kinetics was unaffected by training status; the faster muscle deoxyhaemoglobin kinetics in the trained subjects thus indicates slower blood flow kinetics during recovery from exercise compared to the untrained subjects.     

Effect of sprint interval training on circulatory function during exercise in sedentary, overweight/obese women

Very high-intensity, low-volume, sprint interval training (SIT) increases muscle oxidative capacity and may increase maximal oxygen uptake ( [(V)\dot]\textO _{2 \textmax} {\dot{V}\text{O}}_{{ 2 {\text{max}}}} ), but whether circulatory function is improved, and whether SIT is feasible in overweight/obese women is unknown. To examine the effects of SIT on [(V)\dot]\textO _{2 \textmax} {\dot{V}\text{O}}_{{ 2 {\text{max}}}} and circulatory function in sedentary, overweight/obese women. Twenty-eight women with BMI > 25 were randomly assigned to SIT or control (CON) groups. One week before pre-testing, subjects were familarized to [(V)\dot]\textO _{2 \textmax} {\dot{V}\text{O}}_{{ 2 {\text{max}}}} testing and the workload that elicited 50% [(V)\dot]\textO _{2 \textmax} {\dot{V}\text{O}}_{{ 2 {\text{max}}}} was calculated. Pre- and post-intervention, circulatory function was measured at 50% of the pre-intervention [(V)\dot]\textO _{2 \textmax} {\dot{V}\text{O}}_{{ 2 {\text{max}}}} , and a GXT was performed to determine [(V)\dot]\textO _{2 \textmax} {\dot{V}\text{O}}_{{ 2 {\text{max}}}} . During the intervention, SIT training was given for 3 days/week for 4 weeks. Training consisted of 4–7, 30-s sprints on a stationary cycle (5% body mass as resistance) with 4 min active recovery between sprints. CON maintained baseline physical activity. Post-intervention, heart rate (HR) was significantly lower and stroke volume (SV) significantly higher in SIT (−8.1 and 11.4%, respectively; P < 0.05) during cycling at 50% [(V)\dot]\textO _{2 \textmax} {\dot{V}\text{O}}_{{ 2 {\text{max}}}} ; changes in CON were not significant (3 and −4%, respectively). Changes in cardiac output ( [(\textQ)\dot] {\dot{\text{Q}}} ) and arteriovenous oxygen content difference [(a − v)O₂ diff] were not significantly different for SIT or CON. The increase in [(V)\dot]\textO _{2 \textmax} {\dot{V}\text{O}}_{{ 2 {\text{max}}}} by SIT was significantly greater than by CON (12 vs. −1%). Changes by SIT and CON in HR_max (−1 vs. −1%) were not significantly different. Four weeks of SIT improve circulatory function during submaximal exercise and increases [(V)\dot]\textO _{2 \textmax} {\dot{V}\text{O}}_{{ 2 {\text{max}}}} in sedentary, overweight/obese women.     

Erratum to: Blood HbO2 and HbCO2 Dissociation Curves at Varied O2, CO2, pH, 2,3-DPG and Temperature Levels

New mathematical model equations for O₂ and CO₂ saturations of hemoglobin ( S_{\textHbO 2} S_{{{\text{HbO}}_{ 2} }} and S_{\textHbCO 2} S_{{{\text{HbCO}}_{ 2} }} ) are developed here from the equilibrium binding of O₂ and CO₂ with hemoglobin inside RBCs. They are in the form of an invertible Hill-type equation with the apparent Hill coefficients K_{\textHbO 2} K_{{{\text{HbO}}_{ 2} }} and K_{\textHbCO 2} K_{{{\text{HbCO}}_{ 2} }} in the expressions for S_{\textHbO 2} S_{{{\text{HbO}}_{ 2} }} and S_{\textHbCO 2} S_{{{\text{HbCO}}_{ 2} }} dependent on the levels of O₂ and CO₂ partial pressures ( P_{\textO 2} P_{{{\text{O}}_{ 2} }} and P_{\textCO 2} P_{{{\text{CO}}_{ 2} }} ), pH, 2,3-DPG concentration, and temperature in blood. The invertibility of these new equations allows P_{\textO 2} P_{{{\text{O}}_{ 2} }} and P_{\textCO 2} P_{{{\text{CO}}_{ 2} }} to be computed efficiently from S_{\textHbO 2} S_{{{\text{HbO}}_{ 2} }} and S_{\textHbCO 2} S_{{{\text{HbCO}}_{ 2} }} and vice versa. The oxyhemoglobin (HbO₂) and carbamino-hemoglobin (HbCO₂) dissociation curves computed from these equations are in good agreement with the published experimental and theoretical curves in the literature. The model solutions describe that, at standard physiological conditions, the hemoglobin is about 97.2% saturated by O₂ and the amino group of hemoglobin is about 13.1% saturated by CO₂. The O₂ and CO₂ content in whole blood are also calculated here from the gas solubilities, hematocrits, and the new formulas for S_{\textHbO 2} S_{{{\text{HbO}}_{ 2} }} and S_{\textHbCO 2} S_{{{\text{HbCO}}_{ 2} }} . Because of the mathematical simplicity and invertibility, these new formulas can be conveniently used in the modeling of simultaneous transport and exchange of O₂ and CO₂ in the alveoli–blood and blood–tissue exchange systems.