Physiological responses to hypoxic constant-load and high-intensity interval exercise sessions in healthy subjects.

PURPOSE: The aim of this study was to assess the acute cardiorespiratory as well as muscle and cerebral tissue oxygenation responses to submaximal constant-load (CL) and high-intensity interval (HII) cycling exercise performed in normoxia and in hypoxia at similar intensity, reproducing whole-body endurance exercise training sessions as performed in sedentary and clinical populations. METHODS: Healthy subjects performed two CL (30 min, 75% of maximal heart rate, n = 12) and two HII (15 times 1-min high-intensity exercise-1-min passive recovery, n = 12) cycling exercise sessions in normoxia and in hypoxia [mean arterial oxygen saturation 76 ± 1% (clamped) during CL and 77 ± 5% (inspiratory oxygen fraction 0.135) during HII]. Cardiorespiratory and near-infrared spectroscopy parameters as well as the rate of perceived exertion were continuously recorded. RESULTS: Power output was 21 ± 11% and 15% (according to protocol design) lower in hypoxia compared to normoxia during CL and HII exercise sessions, respectively. Heart rate did not differ between normoxic and hypoxic exercise sessions, while minute ventilation was higher in hypoxia during HII exercise only (+ 13 ± 29%, p < 0.05). Quadriceps tissue saturation index did not differ significantly between normoxia and hypoxia (CL 60 ± 8% versus 59 ± 5%; HII 59 ± 10% versus 56 ± 9%; p > 0.05), while prefrontal cortex deoxygenation was significantly greater in hypoxia during both CL (66 ± 4% versus 56 ± 6%) and HII (58 ± 5% versus 55 ± 5%; p < 0.05) sessions. The rate of perceived exertion did not differ between normoxic and hypoxic CL (2.4 ± 1.7 versus 2.9 ± 1.8) and HII (6.9 ± 1.4 versus 7.5 ± 0.8) sessions (p > 0.05). CONCLUSION: This study indicates that at identical heart rate, reducing arterial oxygen saturation near 75% does not accentuate muscle deoxygenation during both CL and HII exercise sessions compared to normoxia. Hence, within these conditions, larger muscle hypoxic stress should not be expected.

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.

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.

Is tryptophan metabolism involved in sleep apnea-related cardiovascular co-morbidities and cancer progression?

Obstructive sleep apnea (OSA) is a multi-component chronic disease affecting 6-17% of adults in the general population. The main hallmark of OSA, intermittent hypoxia (IH), is reported as the main trigger for cardiometabolic co-morbidities. Recent studies, both in rodent models exposed to IH and in humans, have suggested an enhanced incidence and accelerated progression of cancer. However, mechanisms underlying the relationships between OSA and cardiovascular disease on one hand, and cancer on the other hand, have not been entirely deciphered yet. Tryptophan (TRP) metabolism results in nicotinamid and serotonin production, but also in the production of numerous intermediates such as kynurenine, anthranilic and kynurenic acids, 3-hydroxykynurenine, 3-hydroxyanthranilic and quinolinic acids. Each of these metabolites has been linked to cardiovascular disease and cancer mainly in epidemiologic studies. We hypothesize that an alteration of TRP metabolism may play a role in OSA-related cardiovascular co-morbidities and might be one of the players in the relationship between cancer and intermittent hypoxia/OSA. If this is true, interventions aiming to modify TRP metabolism, may constitute a new therapeutic strategy against cardiovascular disease progression and cancer occurrence in OSA populations.

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.

Cardiac output response to dynamic exercise after atrial switch repair for transposition of the great arteries.

Results from this study showed that patients who underwent successful operation for transposition of the great arteries had no appropriate increase in stroke volume in response to exercise of a nature similar to common recreational activities. The impairment, most likely due to disturbances in both venous return and ventricular systolic function, is compensated for by an increase in peripheral oxygen extraction; however, this increase may not be adequate with maturation or during prolonged exercise when cardiovascular constraints are more important.

Early onset of pulmonary gas exchange disturbance during progressive exercise in healthy active men.

Some recent studies of competitive athletes have shown exercise-induced hypoxemia to begin in submaximal exercise. We examined the role of ventilatory factors in the submaximal exercise gas exchange disturbance (GED) of healthy men involved in regular work-related exercise but not in competitive activities. From the 38 national mountain rescue workers evaluated (36 +/- 1 yr), 14 were classified as GED and were compared with 14 subjects matched for age, height, weight, and maximal oxygen uptake (VO2 max; 3.61 +/- 0.12 l/min) and showing a normal response (N). Mean arterial PO2 was already lower than N (P = 0.05) at 40% VO2 max and continued to fall until VO2 max (GED: 80.2 +/- 1.6 vs. N: 91.7 +/- 1.3 Torr). A parallel upward shift in the alveolar-arterial oxygen difference vs. %VO2 max relationship was observed in GED compared with N from the onset throughout the incremental protocol. At submaximal intensities, ideal alveolar PO2, tidal volume, respiratory frequency, and dead space-to-tidal volume ratio were identical between groups. As per the higher arterial PCO2 of GED at VO2 max, subjects with an exaggerated submaximal alveolar-arterial oxygen difference also showed a relative maximal hypoventilation. Results thus suggest the existence of a common denominator that contributes to the GED of submaximal exercise and affects the maximal ventilatory response.

Hormonal responses to exercise during moderate cold exposure in young vs. middle-age subjects.

The influence of moderate cold exposure on the hormonal responses of atrial natriuretic factor (ANF), arginine vasopressin (AVP), catecholamines, and plasma renin activity (PRA) after exhaustive exercise was studied in 9 young and 10 middle-aged subjects. Exercise tests were randomly performed in temperate (30 degrees C) and cold (10 degrees C) environments. Heart rate, oxygen consumption, and peripheral arterial blood pressure were measured at regular intervals. Blood samples were collected before and immediately after exercise at 30 or 10 degrees C. Plasma sodium and potassium concentrations as well as hemoglobin and hematocrit were measured, and the change in plasma volume was calculated. At rest and during exercise, oxygen consumption was similar during exposure to both temperate and cold temperatures. During submaximal exercise intensities, the rise in heart rate was blunted while the increase in systolic blood pressure was significantly greater at 10 than at 30 degrees C. The increases in plasma sodium and potassium concentrations after exhaustion were similar between environments, as was the decrease in plasma volume. In both groups, all plasma hormones were significantly elevated postexercise, with the AVP response similar at 10 and 30 degrees C. However, the norepinephrine and ANF responses were significantly greater while the PRA response was significantly reduced at 10 degrees C. In the middle-aged subjects the epinephrine response to exercise was higher at 10 than at 30 degrees C. The greater ANF and reduced PRA responses to exercise in the cold may have resulted from central hemodynamic changes caused by cold-induced cutaneous vasoconstriction.(ABSTRACT TRUNCATED AT 250 WORDS)

Nitric oxide response in exhaled air during an incremental exhaustive exercise.

This study examines the response of the exhaled nitric oxide (NO) concentration (CNO) and the exhaled NO output (VNO) during incremental exercise and during recovery in six sedentary women, seven sedentary men, and eight trained men. The protocol consisted of increasing the exercise intensity by 30 W every 3 min until exhaustion, followed by 5 min of recovery. Minute ventilation (VE), oxygen consumption (VO2), carbon dioxide production, heart rate, CNO, and VNO were measured continuously. The CNO in exhaled air decreased significantly provided that the exercise intensity exceeded 65% of the peak VO2. It reached similar values, at exhaustion, in all three groups. The VNO increased proportionally with exercise intensity up to exhaustion and decreased rapidly during recovery. At exhaustion, the mean values were significantly higher for trained men than for sedentary men and sedentary women. During exercise, VNO correlates well with VO2, carbon dioxide production, VE, and heart rate. For the same submaximal intensity, and thus a given VO2 and probably a similar cardiac output, VNO appeared to be similar in all three groups, even if the VE was different. These results suggest that, during exercise, VNO is mainly related to the magnitude of aerobic metabolism and that this relationship is not affected by gender differences or by noticeable differences in the level of physical training.

Commercialization of veterinary viral vaccines.

If vaccines are to reliably prevent disease, they must be developed, produced and quality-controlled according to very strict regulations and procedures. Veterinary viral vaccine registrations are governed by different rules in different countries, but these rules all emphasize that the quality of the raw materials--the cells, eggs, animals or plants that are used in production--need to be carefully controlled. The veterinary vaccine business is also very cost-conscious. Emphasis over the last 5-10 years has therefore been to develop culture systems that minimize labor and sterility problems and thus provide for reliable and cost-effective production. Implementing these often more complex systems in a production environment takes considerable effort, first in scale-up trials and further down the line in convincing production personnel to change their familiar system for something new and possibly untried. To complete scale-up trials successfully, it is absolutely necessary to understand the biochemistry of the cells and the influence of the virus on the cells under scale-up and later production conditions. Once a viral product can be produced on a large scale, it is imperative that the quality of the end-product is controlled in an intelligent way. One needs to know whether the end-product performs in the animal as was intended during its conception in the research and development department. The development of the appropriate tests to demonstrate this plays an important role in the successful development of a vaccine.

[Cardiorespiratory and metabolic changes during prolonged exercise at 50% of the maximal load. Application to rehabilitation of severe cardiac insufficiencies]. / Modifications cardiorespiratoires et métaboliques au cours d'un effort prolongé à 50% de la charge maximale. Application à la rééducation des insuffisants cardiaques sévères.

The object of physical training in patients with chronic cardiac failure and severe left ventricular dysfunction is to improve skeletal muscle adaptation without impairing myocardial function. It is acknowledged that aerobic exercise limits increased ventricular strain. Therefore, the authors decided to determine whether exercise at 50% maximal power load constituted aerobic training. Eight patients with chronic cardiac failure (age 57 +/- 10 years; resting radionuclide ejection fraction: 25 +/- 5%) performed a rectangular submaximal exercise for 20 minutes at 50% of maximal aerobic load (MAL) as determined by a prior triangular exercise test at 10 W/mn (MAL = 92 +/- 26 Watts-Peak VO2 = 14.8 +/- 2.4 ml/Kg/mn). Gaseous exchanges (VO2, VCO2) minute volume (MV) and serum lactates were measured at rest and every 5 minutes during exercise. MV, VO2 and VCO2 increased significantly (p < 0.005) with a change of less than 5% between the 20th and 10th minute. Respiratory quotient was unchanged until the end of exercise and serum lactate levels stabilised between the 10th (3.4 +/- 0.66 mmol/l) and the 20th minute of exercise (3.5 +/- 0.47 mmol/l). No significant relationship was observed between ventilation and serum lactate or between respiratory quotient and serum lactate. These results confirm that exercise at 50% of maximal load is aerobic training even in patients with severe left ventricular dysfunction. This parameter would appear to be more useful than using the heart rate which is often abnormal in chronic cardiac failure (abnormal chronotropic response, atrial or ventricular arrhythmias).

[Cardiac output evaluation during exercise in children treated with atrial surgery for transposition of great vessels]. / Evaluation du débit cardiaque à l'exercice chez des enfants traités par chirurgie atriale d'une transposition des gros vaisseaux.

The long-term physiopathological consequences of atrial surgery (Senning or Mustard procedures) for transposition of the great vessels with respect to exercise capacity are not well known. We measured the cardiac index by the technique of CO2 rebreathing at two submaximal levels of exercise corresponding to a stable oxygen consumption of 20 (E20) and 30 (E30) ml/min/kg in 7 patients successfully operated for transposition of the great vessels and in 7 control children paired for age, gender and body surface area. Despite an identical chronotropic response to exercise in the two groups, the increase in cardiac index was not as great in the children operated for transposition (from 6.86 +/- 0.51 to 7.71 +/- 0.78 l/min/m2) as in the control population (from 7.71 +/- 0.78 to 10.2 +/- 0.51 l/min/m2; p < 0.02). The stroke volume index was therefore significantly lower in the transposition group at both levels of exercise (52 +/- 3.2 vs 63 +/- 4.1 ml/m2; p < 0.04 at E20; and 46.4 +/- 4.3 vs 66 +/- 5.1 ml/m2 at E30). The main cause of this reduction of the stroke volume index is probably a lack of adaptation of right ventricular systolic function on exercise but it is not possible to exclude diastolic dysfunction due to reduce compliance secondary to the intraatrial patch. The conditions of preload are in fact instrumental in increasing stroke volume index at submaximal exercise levels.

[Diagnostic use of oxygen consumption and gas exchange in exercise testing]. / Usage diagnostique de la consommation d'oxygène et des échanges gazeux au cours de l'épreuve d'exercice.

The interpretation of cardio-pulmonary exercise testing is usually performed on successive decisional organigrams which are based on the normality of two initial main branchpoints i.e., Vo2max and ventilatory threshold (VThr). This didactic approach leads however to a simplistic approach of exercise pathophysiology because the answer to the two original branchpoints (Vo2max and VThr) is mainly binary whereas the physiological meaning of these two parameters is multifactorial. Thus, we propose a methodic analytical approach which allows to integrate step by step the various informations concerning aerobic capacity, ventilatory and cardiocirculatory responses, and acidobasic status. After a purely descriptive analysis of data , a first synthesis describes the physiopathological behaviour during exercise and states the specificity of these informations excluding usual confounding factors. The comparison between the functional data and the clinical informations allows to propose some physiopathological hypothesis by confronting several complementary approaches: physiological, physiopathological and clinical ones. This method seems to be more adapted to the clinical diagnostic use of such a physiological investigation because it is sensitive, reproducible but not specific.

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.

Maximal and submaximal treadmill tests in a young adult with fragile-X syndrome.

Fragile X syndrome is associated with expansion of a CGG triplet repeat in the FMR1 gene, which abolishes production of the FMRP protein. This abnormality is expressed as a number of neuro-endocrine disorders (the adrenal axis, macroorchidism) and the emergence of significant behavioural stress. Here, we report on the hormonal status of a young adult with fragile X syndrome, with a focus on catecholamine and cortisol changes during a submaximal treadmill test. The patient showed abnormally high epinephrine and norepinephrine concentrations. During a submaximal incremental test, cortisol levels were higher than the laboratory reference range. Although the submaximal incremental test has a significant "stressful" effect, this young adult was able to complete the entire protocol without any maladaptive behaviour or withdrawal.

Are hormonal responses to exercise in young men with Down's syndrome related to reduced endurance performance?

The aim of the present study was to analyse whether hormonal responses could explain an exercise limitation in Down's syndrome (DS). Fourteen young men with DS (mean age 22.5 +/- 0.7 years) and 15 controls (CONT, mean age 22.5 +/- 0.3 years) participated in the study. During a treadmill submaximal incremental test, blood samples were collected for determination of hormonal and metabolic variables. Compared to CONT, DS individuals showed lower VO(2max) (P < 0.05), and lower duration of submaximal incremental exercise (P < 0.001). At rest, DS individuals showed greater catecholamines, insulin and leptin values (P < 0.05), but lower testosteronemia and cortisolemia (P < 0.05), compared to CONT. During submaximal incremental tests, catecholamines and cortisol were not increased, whereas the insulin concentration of DS individuals was significantly higher (P < 0.01) compared to CONT. Glycaemia increased significantly at the end of submaximal incremental test for CONT but not for DS individuals (P < 0.01). Maximal fat oxidation was lower (P < 0.01), whereas non-esterified fatty acids concentrations rose significantly during submaximal exercise in DS individuals. These results indicate an altered hormonal response to exercise in DS individuals. This endocrine profile at rest and during exercise may limit endurance performance in DS individuals.

Laboratory running test vs. field roller skiing test in cross-country skiers: a longitudinal study.

Laboratory treadmill running tests are commonly used to assess the effect of training programs and to prescribe training intensity for cross-country skiers. The present study compared the physiological parameters during a treadmill running (R) test and a field roller skiing (RS) test both at the beginning (Beg) and at the end (End) of a 6-month specific training program in seven competitive cross-country skiers. Oxygen uptake (VO2) and blood lactate concentration ([La]) were assessed for exercise intensity corresponding to 70%, 80%, 90% of maximal heart rate (HRmax) and to HRmax.VO2 was lower for the RS test compared to the R test at any HR levels at Beg only (p<0.05). Maximal VO2 increased from Beg to End for the RS test only (+23.7+/-10.4; p<0.05). [La] was lower for the R test compared to the RS test during both testing periods at 90% HRmax (p<0.05), and no significant modification in [La] from Beg to End at any HR levels was observed (p>0.05). The [La]/V.O2 curve shifted toward the right from Beg to End to a greater extent for the RS test compared to the R test. The present study emphasised the importance of exercise specificity in order to assess the effect of specific training program in competitive cross-country skiers.

Exhaled nitric oxide in single and repetitive prolonged exercise.

This study was performed to determine the influence of single and repetitive exercise on nitric oxide (NO) concentration in the lung. Exhaled NO concentration (FE(NO)) was measured during a constant-flow exhalation manoeuvre (170 ml x s(-1), against a 10 cmH2O resistance) in healthy individuals (a) during and after a 100-min square-wave exercise of between 25 and 60% of maximal power output (n = 18) and (b) before and after five successive prolonged exercises (90-120 min, 75-85% of maximal heart rate) separated by 48 or 24 h (n = 8). The FE(NO0.170) was decreased during and after the 100-min exercise test (mean +/- s(x): 58.5 +/- 3.7% and 76.7 +/- 5.2% of resting value at 90 min of exercise and 15 min post-exercise, respectively; P < 0.05). The five successive exercise sessions induced a similar post-exercise FE(NO0.170) decrement (73.1 +/- 2.9% of resting value 15 min post-exercise), while basal FE(NO0.170) values were not different between the five sessions (P > 0.05). These results suggest that prolonged exercise induces a reduction in NO concentration within the lung that lasts for several minutes after the end of exercise. However, repetitive exercises (at least every 24 h) allow complete NO recovery from one session to another. The implication of such a decrease in NO availability within the lung remains to be clarified.