[Adaptation to altitude in respiratory diseases]. / Adaptation à l'altitude dans les maladies respiratoires.

The frequency of high-altitude sojourns (for work, leisure, air travel or during car/train journeys) justifies the question of their tolerance, especially in people with pre-existing respiratory disease. Reduced barometric pressure and abrupt variations in temperature and inhaled air density may be responsible for modifications affecting the respiratory system and, in fine, oxygenation. These modifications may compromise altitude tolerance, further worsen respiratory dysfunction and render physical exercise more difficult. In obstructive lung disease, altitude is associated with gas exchange impairment, increased ventilation at rest and during exercise and heightened pulmonary artery pressure through hypoxic vasoconstriction, all of which may worsen dyspnea and increase the risk of altitude intolerance (acute mountain sickness, AMS). The most severe patients require rigorous evaluation, and hypoxic testing can be proposed. People with mild to moderate intermittent asthma can plan high altitude sojourns, provided that they remain under control at night and during exercise, and follow an adequate action plan in case of exacerbation. Respiratory disease patients with pulmonary artery hypertension (PAH) and chemoreflex control abnormalities need to be identified as at risk of altitude intolerance.

Exercise-induced laryngeal obstruction: From clinical examination to continuous laryngoscopy during exercise.

The diagnosis of exercise-induced laryngeal obstruction (EILO) should be suspected when exercise triggers inspiratory stridor. EILO is common in adolescent populations and has a significant impact on sports. Identification of laryngeal obstruction during continuous laryngoscopy during exercise (CLE) is the gold standard diagnostic tool for this disorder, which is not widely known in France. The challenge faced by otolaryngologists is to identify, among patients referred by pulmonologists or sports physicians, those with exercise-induced inspiratory symptoms or poorly controlled exercise-induced asthma, in whom a diagnosis of EILO is strongly suspected. Laryngoscopy at rest may reveal a laryngeal, glottic or supraglottic abnormality predictive of obstruction at increased inspiratory airflow. When pulmonary function tests are normal or in the case of failure of treatment of exercise-induced asthma, the otolaryngologist must complete the examination by a CLE test to confirm the diagnosis of EILO and identify the site of obstruction. This examination is well tolerated, minimally invasive and allows identification of the site of airflow obstruction, allowing specific conservative or surgical treatment. This technical note describes in detail clinical examination and CLE testing in patients with suspected EILO.

[Guidelines for methacholine provocation testing]. / Recommandations pour le test de provocation bronchique à la méthacholine en pratique clinique, à partir de l'âge scolaire.

Bronchial challenge with the direct bronchoconstrictor agent methacholine is commonly used for the diagnosis of asthma. The "Lung Function" thematic group of the French Pulmonology Society (SPLF) elaborated a series of guidelines for the performance and the interpretation of methacholine challenge testing, based on French clinical guideline methodology. Specifically, guidelines are provided with regard to the choice of judgment criteria, the management of deep inspirations, and the role of methacholine bronchial challenge in the care of asthma, exercise-induced asthma, and professional asthma.

Absence of calf muscle metabolism alterations in active cystic fibrosis adults with mild to moderate lung disease.

BACKGROUND: Specific alterations in skeletal muscle related to genetic defects may be present in adults with cystic fibrosis (CF). Limb muscle dysfunction may contribute to physical impairment in CF. AIMS AND OBJECTIVES: We hypothesized that adults with CF would have altered calf muscle metabolism during exercise. METHODS: Fifteen adults with CF and fifteen healthy controls matched for age, gender and physical activity performed a maximal cycling test and an evaluation of calf muscle energetics by 31P magnetic resonance spectroscopy before, during and after plantar flexions to exhaustion. RESULTS: Maximal cycling test revealed lower exercise capacities in CF (VO2peak 2.44±0.11 vs. 3.44±0.23L·Min-1, P=0.03). At rest, calf muscle phosphorus metabolites and pHi were similar in CF and controls (P>0.05). Maximal power output during plantar flexions was significantly lower in CF compared to controls (7.8±1.2 vs. 6.6±2.4W; P=0.013). At exhaustion, PCr concentration was similarly reduced in both groups (CF -33±7%, controls -34±6%, P=0.44), while PCr degradation at identical absolute workload was greater in CF patients (P=0.04). These differences disappeared when power output was normalized for differences in calf size (maximal power output: 0.10±0.02 vs. 0.10±0.03W/cm2; P=0.87). Pi/PCr ratio and pHi during exercise as well as PCr recovery after exercise were similar between groups. CONCLUSION: Similar metabolic calf muscle responses during exercise and recovery were found in CF adults and controls. Overall, muscle anabolism rather than specific metabolic dysfunction may be critical regarding muscle function in CF.

Sleep quality, sleep duration and physical activity in obese adolescents: effects of exercise training.

BACKGROUND: Decreased sleep duration and altered sleep quality are risk factors for obesity in youth. Structured exercise training has been shown to increase sleep duration and improve sleep quality. OBJECTIVES: This study aimed at evaluating the impact of exercise training for improving sleep duration, sleep quality and physical activity in obese adolescents (OB). METHODS: Twenty OB (age: 14.5 ± 1.5 years; body mass index: 34.0 ± 4.7 kg m(-2) ) and 20 healthy-weight adolescents (HW) completed an overnight polysomnography and wore an accelerometer (SenseWear Bodymedia) for 7 days. OB participated in a 12-week supervised exercise-training programme consisting of 180 min of exercise weekly. Exercise training was a combination of aerobic exercise and resistance training. RESULTS: Sleep duration was greater in HW compared with OB (P < 0.05). OB presented higher apnoea-hypopnoea index than HW (P < 0.05). Physical activity (average daily metabolic equivalent of tasks [METs]) by accelerometer was lower in OB (P < 0.05). After exercise training, obese adolescents increased their sleep duration (+64.4 min; effect size: 0.88; P = 0.025) and sleep efficiency (+7.6%; effect size: 0.76; P = 0.028). Physical activity levels were increased in OB as evidenced by increased steps per day and average daily METs (P < 0.05). Improved sleep duration was associated with improved average daily METs (r = 0.48, P = 0.04). CONCLUSION: The present study confirms altered sleep duration and quality in OB. Exercise training improves sleep duration, sleep quality and physical activity.

Impact of exercise training without caloric restriction on inflammation, insulin resistance and visceral fat mass in obese adolescents.

BACKGROUND: Exercise training has been shown to improve cardiometabolic health in obese adolescents. OBJECTIVES: Evaluate the impact of a 12-week exercise-training programme (without caloric restriction) on obese adolescents' cardiometabolic and vascular risk profiles. METHODS: We measured systemic markers of oxidation, inflammation, metabolic variables and endothelial function in 20 obese adolescents (OB) (age: 14.5 ± 1.5 years; body mass index: 34.0 ± 4.7 kg m(-2) ) and 20 age- and gender-matched normal-weight adolescents (NW). Body composition was assessed by magnetic resonance imagery. Peak aerobic capacity and maximal fat oxidation were evaluated during specific incremental exercise tests. OB participated in a 12-week exercise-training programme. RESULTS: OB presented lower peak aerobic capacity (24.2 ± 5.9 vs. 39.8 ± 8.3 mL kg(-1) min(-1) , P < 0.05) and maximal fat oxidation compared with NW (P < 0.05). OB displayed greater F2t-Isoprostanes (20.5 ± 6.7 vs. 13.4 ± 4.2 ng mmol(-1) creatinine), Interleukin-1 receptor antagonist (IL-1Ra) (1794.8 ± 532.2 vs. 835.1 ± 1027.4 pg mL(-1) ), Tumor Necrosis Factor-α (TNF-α) (2.1 ± 1.2 vs. 1.5 ± 1.0 pg mL(-1) ), Soluble Tumor Necrosis Factor-α Type II Receptor (sTNFαRII), leptin, insulin, homeostasis model assessment of insulin resistance, version 2 (HOMA2-IR), high-sensitive C-reactive protein, triglycerides and lower adiponectin and high-density lipoprotein cholesterol (all P < 0.05). After exercise training, despite lack of weight loss, VO2peak (mL.kg(-1) .min(-1) ) and maximal fat oxidation increased (P < 0.05). IL-1Ra and IFN-gamma-inducible protein 10 (IP-10) decreased (P < 0.05). Insulin and HOMA2-IR decreased (14.8 ± 1.5 vs. 10.2 ± 4.2 µUI mL(-1) and 1.9 ± 0.8 vs. 1.3 ± 0.6, respectively, P < 0.05). Change in visceral fat mass was inversely associated with change in maximal fat oxidation (r = -0.54; P = 0.024). The subgroup of participants that lost visceral fat mass showed greater improvements in triglycerides, insulin resistance and maximal fat oxidation. CONCLUSION: Our data confirms the role of exercise training on improving the inflammatory profile and insulin resistance of OB in the absence of weight loss. However, those who lost a greater amount of visceral fat mass showed greater benefits in terms of insulin profile, triglycerides and maximal fat oxidation.

Impact of salbutamol on muscle metabolism assessed by ³¹P NMR spectroscopy.

The potential ergogenic effects of oral salbutamol intake were demonstrated for decades but the underlying mechanisms remain to elucidate. We hypothesized that improved exercise performance after acute oral salbutamol administration is associated with changes in muscle metabolism. Twelve healthy, nonasthmatic, moderately trained, male subjects were recruited to compare in a double-blind crossover randomized study, an oral dose of salbutamol (4 mg) and a placebo. After treatment administration, subjects performed repetitive plantar flexions to exhaustion in a 3T magnet. Continuous (31) P nuclear magnetic resonance spectroscopy assessment of the calf muscles was performed at rest, during exercise, and during recovery. No significant difference between treatments was detected in metabolite concentration at rest (P > 0.05). Creatine phosphate and inorganic phosphate changes during and immediately after exercise were similar between treatments (P > 0.05). Intramuscular pH (pHi) was significantly higher at rest, at submaximal exercise but not at exhaustion with salbutamol (pHi at 50% of exercise duration, 6.8 ± 0.1/6.9 ± 0.1 for placebo and salbutamol, respectively, P < 0.05). The maximal power (28 ± 7 W/23 ± 7 W; P = 0.001) and total work (1702 ± 442 J/1381 ± 432 J; P = 0.003) performed during plantar flexions were significantly increased with salbutamol. Salbutamol induced significant improvement in calf muscle endurance with similar metabolic responses during exercise, except slight differences in pHi. Other mechanisms than changes in muscle metabolism may be responsible for the ergogenic effect of salbutamol administration.

Assessement of quadriceps strength, endurance and fatigue in FSHD and CMT: benefits and limits of femoral nerve magnetic stimulation.

OBJECTIVES: To (i) evaluate the feasibility and the reliability of a test assessing quadriceps strength, endurance and fatigue in patients with fascioscapulohumeral dystrophy (FSHD) and Charcot-Marie-Tooth disease (CMT), (ii) compare quadriceps function between patients and healthy controls. METHODS: Controls performed the test once and patients twice on two separate visits. It involved progressive sets of 10 isometric contractions each followed by neuromuscular assessments with FNMS. RESULTS: Volitional assessment of muscle strength, endurance and fatigue appeared to be reliable in FSHD and CMT patients. Supramaximal FNMS was achieved in ∼70% of FSHD patients and in no CMT patients. In FSHD patients, Femoral nerve magnetic stimulation (FNMS) provided reliable assessment of central (typical error as a coefficient of variation (CVTE)<8% for voluntary activation) and peripheral (CVTE<10% and intraclass coefficient correlation >0.85 for evoked responses) function. Patients and controls had similar reductions in evoked quadriceps responses, voluntary activation and similar endurance. CONCLUSIONS: This test provides reliable evaluation but FNMS exhibits limitations due to insufficient stimulation intensity particularly in neurogenic conditions. It showed similar central and peripheral quadriceps fatigability in patients and controls. SIGNIFICANCE: This test may be a valuable tool for patient follow-up although further development of magnetic stimulation devices is needed to extend its applicability.

Potential interests and limits of magnetic and electrical stimulation techniques to assess neuromuscular fatigue.

Neuromuscular function can change under different conditions such as ageing, training/detraining, long-term spaceflight, environmental conditions (e.g. hypoxia, hyperthermia), disease, therapy/retraining programs and also with the appearance of fatigue. Neuromuscular fatigue can be defined as any decrease in maximal voluntary strength or power. There is no standardized method to induce fatigue and various protocols involving different contraction patterns (such as sustained or intermittent submaximal isometric or dynamic contractions on isokinetic or custom chairs) have been used. Probably due to lack of motivation/cooperation, results of fatigue resistance protocols are more variable in patients than in healthy subjects. Magnetic and electrical stimulation techniques allow non-invasive assessment of central and peripheral origins of fatigue. They also allow investigation of different types of muscle fatigue when combining various types of stimulation with force/surface EMG measurements. Since maximal electrical stimuli may be uncomfortable or even sometimes painful, several alternative methods have been recently proposed: submaximal muscle stimulation, low/high-frequency paired pulses instead of tetanic stimuli and the use of magnetic stimulation at the peripheral level.

Time-dependent effect of acute hypoxia on corticospinal excitability in healthy humans.

Contradictory results regarding the effect of hypoxia on cortex excitability have been reported in healthy subjects, possibly depending on hypoxia exposure duration. We evaluated the effects of 1- and 3-h hypoxia on motor corticospinal excitability, intracortical inhibition, and cortical voluntary activation (VA) using transcranial magnetic stimulation (TMS). TMS to the quadriceps cortex area and femoral nerve electrical stimulations were performed in 14 healthy subjects. Motor-evoked potentials (MEPs at 50-100% maximal voluntary contraction; MVC), recruitment curves (MEPs at 30-100% maximal stimulator power output at 50% MVC), cortical silent periods (CSP), and VA were measured in normoxia and after 1 (n = 12) or 3 (n = 10) h of hypoxia (Fi(O(2)) = 0.12). One-hour hypoxia did not modify any parameters of corticospinal excitability but reduced slightly VA, probably due to the repetition of contractions 1 h apart (96 ± 4% vs. 94 ± 4%; P = 0.03). Conversely, 3-h hypoxia significantly increased 1) MEPs of the quadriceps muscles at all force levels (+26 ± 14%, +24 ± 12%, and +27 ± 17% at 50, 75, and 100% MVC, respectively; P = 0.01) and stimulator power outputs (e.g., +21 ± 14% at 70% maximal power), and 2) CSP at all force levels (+20 ± 18%, +18 ± 19%, and +14 ± 22% at 50, 75, and 100% MVC, respectively; P = 0.02) and stimulator power outputs (e.g., +9 ± 8% at 70% maximal power), but did not modify VA (98 ± 1% vs. 97 ± 3%; P = 0.42). These data demonstrate a time-dependent hypoxia-induced increase in motor corticospinal excitability and intracortical inhibition, without changes in VA. The impact of these cortical changes on physical or psychomotor performances needs to be elucidated to better understand the cerebral effects of hypoxemia.

Can crossover and maximal fat oxidation rate points be used equally for ergocycling and walking/running on a track?

AIM: To verify whether exercise intensities at the crossover point (COP) and maximal lipid oxidation (Lipox(max)) can be used interchangeably regardless of exercise mode, this study compared COP, Lipox(max) and maximal fat oxidation rate (MFO) obtained during two modes of submaximal metabolic exercise tests: stationary cycling under laboratory conditions and walking/running on a track. METHODS: After preliminary indirect maximal progressive tests, 15 healthy subjects randomly performed submaximal exercise tests on a stationary cycle ergometer (E) and on a track (T), during which gas exchanges and substrate oxidation rates were measured. RESULTS: There were no significant mean differences in COP [heart rate (HR): 149±23 beats.min(-1) (T), 145±28 beats.min(-1) (E); VO(2): 2168±896 mL.min(-1) (T), 2052±714 mL.min(-1) (E)], Lipox(max) [HR: 127±27 beats.min(-1) (T), 126±23 beats.min(-1) (E); VO(2): 1638±839 mL.min(-1) (T), 1696±656 mL.min(-1) (E)] or MFO [498.3±192.0 mg.min(-1) (T), 477.7±221.5 mg.min(-1) (E)] between the two modes of exercise. However, Bland-Altman analysis showed a clear disagreement between the two exercise modes and, in particular, a large random error [bias±random error: for COP, -3.5±53.2 beats.min(-1) (HR), -116.8±1556.4 mL.min(-1) (VO(2)); for Lipox(max), -0.4±43.3 beats.min(-1) (HR), -5.7±1286.4 mL.min(-1) (VO(2)); and for MFO, -20.6±384.9 mg.min(-1)]. CONCLUSION: This study showed that, in young, healthy, reasonably fit subjects, exercise mode can affect intensities at the COP and the Lipox(max). These results, which now have to be confirmed in patients with metabolic defects, suggest the need to perform specific tests to make individualized adaptations to physical activity outside of clinical settings.

Central and peripheral fatigue kinetics during exhaustive constant-load cycling.

The kinetics of central and peripheral fatigue development during an intensive constant-load cycling exercise was evaluated to better understand the mechanisms of task failure. Thirteen males cycled to exhaustion at 80% of maximal power output in intermittent bouts of 6 min of exercise with 4-min break between bouts to assess quadriceps fatigue with maximal voluntary contractions and single (1 Hz), paired (10 and 100 Hz) potentiated and interpolated magnetic stimulations of the femoral nerve (TwQ). Surface electromyographic signals (EMG) of the quadriceps muscles were recorded during stimulations and cycling. Total cycling duration (TCD) was 27 min 38 s±7 min 48 s. The mechanical response evoked by magnetic stimulation decreased mostly during the first half of TCD (TwQ1 Hz reduction: -34.4±12.2% at 40% TCD and -44.8±9.2% at exhaustion; P<0.001), while a reduction in maximum voluntary activation was present toward the end of exercise only (-5.4±4.8% and -6.4±5.6% at 80% TCD and exhaustion, respectively; P<0.01). The increase in quadriceps EMG during cycling was significantly correlated to the TwQ reduction for the rectus femoris (r(2) =0.20 at 1 Hz, r(2) =0.47 at 100 Hz, all P≤0.001). We conclude that peripheral fatigue develops early during constant-load intense cycling and is compensated by additional motor drive, while central fatigue appears to be associated with task failure.

Effects of training at mild exercise intensities on quadriceps muscle energy metabolism in patients with chronic obstructive pulmonary disease.

AIM: To study the effects of physical training at mild intensities on skeletal muscle energy metabolism in eight patients with chronic obstructive pulmonary disease (COPD) and eight paired healthy sedentary subjects. METHODS: Energy metabolism of patients and controls vastus lateralis muscle was studied before and after 3 months of cycling training at mild exercises intensities. RESULTS: The total amount of work accomplished was about 4059 ± 336 kJ in patients with COPD and 7531 ± 1693 kJ in control subjects. This work corresponds to a mechanical power set at 65.2 ± 7.5% of the maximum power for patients with COPD and 52 ± 3.3% of the maximum power in control group. Despite this low level of exercise intensities, we observed an improvement in mitochondrial oxidative phosphorylation through the creatine kinase system revealed by the increased apparent K(m) for ADP (from 105.5 ± 16.1 to 176.9 ± 26.5 µm, P < 0.05 in the COPD group and from 126.9 ± 16.8 to 177.7 ± 17.0, P > 0.05 in the control group). Meanwhile, maximal mechanical and metabolic power increased significantly from 83.1 ± 7.1 to 91.3 ± 7.4 Watts (P < 0.05) and from 16 ± 0.8 to 18.7 ± 0.98 mL O(2) kg(-1) min(-1) (P < 0.05) only in the COPD group. CONCLUSION: This study shows that physical training at mild intensity is able to induce comparable changes in skeletal muscles oxidative energy metabolism in patients with COPD and sedentary healthy subjects, but different changes of maximal mechanical and metabolic power.

Respiratory muscle endurance training in obese patients.

OBJECTIVE: Increased respiratory muscle work is associated with dyspnea and poor exercise tolerance in obese patients. We evaluated the effect of respiratory muscle endurance training (RMET) on respiratory muscle capacities, symptoms and exercise capacity in obese patients. DESIGN: A total of 20 obese patients hospitalized for 26 ± 6 days to follow a low-calorie diet and a physical activity program were included in this case-control study. Of them, 10 patients performed RMET (30-min isocapnic hyperpnea at 60-80% maximum voluntary ventilation, 3-4 times per week during the whole hospitalization period: RMET group), while the other 10 patients performed no respiratory training (control (CON) group). RMET and CON groups were matched for body mass index (BMI) (45 ± 7 kg m(-2)) and age (42 ± 12 years). Lung function, respiratory muscle strength and endurance, 6-min walking distance, dyspnea (Medical Research Council scale) and quality of life (short-form health survey 36 questionnaire) were assessed before and after intervention. RESULTS: Similar BMI reduction was observed after hospitalization in the RMET and CON groups (-2 ± 1 kg m(-2), P < 0.001). No significant change in lung function and respiratory muscle strength was observed except for vital capacity, which increased in the RMET group (+0.20 ± 0.26 l, P = 0.039). Respiratory muscle endurance increased in the RMET group only (+52 ± 27%, P < 0.001). Compared with the CON group, the RMET group had greater improvement in 6MWT (+54 ± 35 versus +1 ± 7 m, P = 0.007), dyspnea score (-2 ± 1 versus -1 ± 1 points, P = 0.047) and quality of life (total score: +251 ± 132 versus +84 ± 152 points, P = 0.018) after hospitalization. A significant correlation between the increase in respiratory muscle endurance and improvement in 6MWT distance was observed (r (2) = 0.36, P = 0.005). CONCLUSIONS: The present study indicates that RMET is feasible in obese patients and can induce significant improvement in dyspnea and exercise capacity. RMET may be a promising tool to improve functional capacity and adherence to physical activities in this population, but further studies are needed to confirm these results.

[Physical activity and exercise training for patients with cystic fibrosis]. / Activité physique et réentraînement à l'effort du patient atteint de mucoviscidose.

In France patients with cystic fibrosis benefit from a multidisciplinary follow-up in Cystic Fibrosis Centres. In this follow-up, despite the numerous therapeutic benefits of exercise in this disease, little emphasis is placed on the promotion of physical activity. The aim of this article is to improve this aspect of management, giving advice from a working group of experts, based on the medical literature and clinical experience. These proposals include quantification of physical activity, evaluation of exercise, training and rehabilitation programs and finally, modification of behaviour to include physical activity in the overall cystic fibrosis treatment strategy. It is intended to set up multicentre studies to evaluate the impact of these proposals.

Respiratory muscle training in athletes with spinal cord injury.

The effect of respiratory muscle endurance training (RMET) on RM function, dyspnoea and exercise performance was evaluated in SCI athletes. Nine endurance athletes (7 paraplegics T4-L1, 2 post-polio syndromes) were evaluated on three occasions (T1-T3), with a 1-month interval between evaluations. Participants performed between T1 and T2 their standard individual exercise training program (control), and between T2 and T3 the same program with 5 additional RMET sessions per week. Each evaluation included: lung function tests, RM strength and endurance tests, a maximal incremental arm cranking test and a field test (simulated competition). Ventilation and dyspnoea were evaluated during each exercise test. Lung function variables and maximal inspiratory strength were not modified (p>0.05) while maximal expiratory strength (+23+/-36 cm H2O; p<0.01) and respiratory endurance (+3 min 33 s+/-2 min 42 s, p<0.01) increased from T2 to T3. During the arm cranking test, exercise duration and maximal power output were slightly increased at T3 compared to T2 (+46+/-39 s, p=0.09 and +8+/-8 W, p=0.08) while ventilation and dyspnoea remained similar. During the field test, exercise time (-10+/-33 s, p=0.37) and ventilation were unchanged but dyspnoea was reduced (-2+/-2 pts, p=0.02) between T2 and T3. We concluded that RMET can improve RM function, reduce the perception of dyspnoea but modifies only slightly exercise performance in SCI athletes.

Methodological aspects of crossover and maximum fat-oxidation rate point determination.

AIM: Indirect calorimetry during exercise provides two metabolic indices of substrate oxidation balance: the crossover point (COP) and maximum fat oxidation rate (LIPOXmax). We aimed to study the effects of the analytical device, protocol type and ventilatory response on variability of these indices, and the relationship with lactate and ventilation thresholds. METHODS: After maximum exercise testing, 14 relatively fit subjects (aged 32+/-10 years; nine men, five women) performed three submaximum graded tests: one was based on a theoretical maximum power (tMAP) reference; and two were based on the true maximum aerobic power (MAP). Gas exchange was measured concomitantly using a Douglas bag (D) and an ergospirometer (E). RESULTS: All metabolic indices were interpretable only when obtained by the D reference method and MAP protocol. Bland and Altman analysis showed overestimation of both indices with E versus D. Despite no mean differences between COP and LIPOXmax whether tMAP or MAP was used, the individual data clearly showed disagreement between the two protocols. Ventilation explained 10-16% of the metabolic index variations. COP was correlated with ventilation (r=0.96, P<0.01) and the rate of increase in blood lactate (r=0.79, P<0.01), and LIPOXmax correlated with the ventilation threshold (r=0.95, P<0.01). CONCLUSION: This study shows that, in fit healthy subjects, the analytical device, reference used to build the protocol and ventilation responses affect metabolic indices. In this population, and particularly to obtain interpretable metabolic indices, we recommend a protocol based on the true MAP or one adapted to include the transition from fat to carbohydrate. The correlation between metabolic indices and lactate/ventilation thresholds suggests that shorter, classical maximum progressive exercise testing may be an alternative means of estimating these indices in relatively fit subjects. However, this needs to be confirmed in patients who have metabolic defects.