Using GPS, accelerometry and heart rate to predict outdoor graded walking energy expenditure.

OBJECTIVES: To determine the best method and combination of methods among global positioning system (GPS), accelerometry, and heart rate (HR) for estimating energy expenditure (EE) during level and graded outdoor walking. DESIGN: Thirty adults completed 6-min outdoor walks at speeds of 2.0, 3.5, and 5.0kmh-1 during three randomized outdoor walking sessions: one level walking session and two graded (uphill and downhill) walking sessions on a 3.4% and a 10.4% grade. EE was measured using a portable metabolic system (K4b2). Participants wore a GlobalSat® DG100 GPS receiver, an ActiGraph™ wGT3X+ accelerometer, and a Polar® HR monitor. Linear mixed models (LMMs) were tested for EE predictions based on GPS speed and grade, accelerometer counts or HR-related parameters (alone and combined). Root-mean-square error (RMSE) was used to determine the accuracy of the models. Published speed/grade-, count-, and HR-based equations were also cross-validated. RESULTS: According to the LMMs, GPS was as accurate as accelerometry (RMSE=0.89-0.90kcalmin-1) and more accurate than HR (RMSE=1.20kcalmin-1) for estimating EE during level walking; GPS was the most accurate method for estimating EE during both level and uphill (RMSE=1.34kcalmin-1)/downhill (RMSE=0.84kcalmin-1) walking; combining methods did not increase the accuracy reached using GPS (or accelerometry for level walking). The cross-validation results were in accordance with the LMMs, except for downhill walking. CONCLUSIONS: Our study provides useful information regarding the best method(s) for estimating EE with appropriate equations during level and graded outdoor walking.

Clinical Interest of Ambulatory Assessment of Physical Activity and Walking Capacity in Peripheral Artery Disease.

The purpose of the present review was to provide, for the first time, a comprehensive analysis and synthesis of the available studies that highlighted the clinical interest of the ambulatory assessment of either physical activity (PA) or walking capacity in patients with lower extremity peripheral artery disease (PAD). We identified 96 related articles published up to March 2015 through a computer-assisted search of the MEDLINE, EMBASE, and Web of Science databases. Ambulatory-measured PA or related energy expenditure (EE) in PAD patients was performed in 87 of the 96 included studies. The main clinical interests of these measurements were (a) the assessment of PA/EE pattern; (b) the characterization of walking pattern; and (c) the control of training load during home-based walking programs. Ambulatory-measured walking capacity was performed in the remaining studies, using either Global Positioning System receivers or the Peripheral Arterial Disease Holter Control device. Highlighted clinical interests were (a) the assessment of community-based walking capacity; (b) the use of new outcomes to characterize walking capacity, besides the conventional absolute claudication distance; and (c) the association with the patient's self-perception of walking capacity. This review also provides for the clinicians step-by-step recommendations to specifically assess PA or walking capacity in PAD patients.

Influence of playing style on the physiological responses of offensive players in table tennis.

AIM: The study aimed to analyse the influence of playing style on the physiological responses of offensive players and on match characteristics during table tennis matches. METHODS: Eight table tennis players were involved in the study. Among them, six players with an offensive playing style (Off) played respectively two matches: one against an offensive player (Off vs. Off matches) and the other one against a defensive opponent (Off vs. Def matches). Duration of rally (DR), real playing time (RPT), effective playing time (EPT), frequency of shots by minutes, and shots per rally were measured. Heart rate (HR) was monitored continuously while rating of perceived exertion (RPE) was obtained after each match. Blood lactate concentrations ([La]) were measured both at the end of each set and at the end of the match. RESULTS: DR (5.4±0.7 s vs. 3.2±0.4 s), RPT, EPT (31.8±5.0% vs. 20.3±1.7%), shots per rally (6.6±0.9 vs. 4.6±0.9), HRmean (146.0±5.9 bpm vs. 139.9±9.0 bpm), HRmean relative to the predicted maximal HR (HRmax-p) (74.8±4.0% vs. 71.7±4.3%) and RPE (7.0±1.1 vs. 5.5±1.5) were significantly higher (P<0.05) in Off vs. Def matches. No significant differences (P>0.05) for HRpeak, [La]mean and [La]peak were noticed between Off vs. Def matches and Off vs. Off matches. CONCLUSIONS: Table tennis playing style influences match characteristics and the offensive player's physiological responses.

Recovery (passive vs. active) during interval training and plasma catecholamine responses.

The effect of recovery mode (Active [AR] vs. Passive [PR]) on plasma catecholamine (Adrenaline [A] and Noradrenaline [NA]) responses to maximal exercise (Exemax) was studied during interval training (IT). 24 male subjects (21.1±1.1 years) were randomly assigned to a control group (CG, n=6), AR training group (ARG, n=9) or PR group (PRG, n=9). ARG and PRG participated in an IT program 3 times a week for 7 weeks. Before and after training, maximal oxygen uptake (VO2max) and maximal aerobic velocity (MAV) were measured. Plasma A and NA were determined at rest, at the end of Exemax and after 10 and 30 min of recovery. Training induced significant changes only in ARG: an increase of VO2max and MAV along with a significant increase of A and NA at the end of Exemax (2.82±0.15 vs. 1.03±0.15 nmol/l and 7.22±0.36 vs. 6.65±0.57 nmol/l, respectively p<0.05). The ratio A/NA measured at the end of Exemax also increased significantly after training (0.41±0.11 vs. 0.16±0.08, P>0.05). The present results show that IT with AR induces a significant increase of A and NA concentrations in response to maximal exercise. The study furthermore shows that IT program with AR may induce more stress than the same program with PR.

A new method to estimate energy expenditure from abdominal and rib cage distances.

The aim of this paper is to validate a new method of energy expenditure (EE) estimation stemming solely from the measurement of rib cage, abdominal and chest wall distances. We set out to prove that the variations of these distances, measured by two pairs of electromagnetic coils, lead to the estimation of the ventilation (VE) and the EE. Eleven subjects were recruited to take part in this study (27.6 ± 5.4 years; 73.7 ± 9.7 kg). Each subject participated in two tests. The objective of Test 1 was to determine the individual and group equations between the VE and EE during light to moderate activities while Test 2 compared the two pairs of electromagnetic coils with the indirect calorimetry so as to estimate EE in upright sitting and standing positions and during walking exercises. During Test 2, we compared EE measured by indirect calorimetry (EE(IC-Val-REF)) with EE estimated by the two pairs of electromagnetic coils through the application of: (1) the individual equation (EE(mag-Val-INDIV)) and (2) the group equation (EE(mag-val-GROUP)). The results show that there is no significant difference between EE(IC-Val-REF) and EE(mag-Val-INDIV) and between EE(IC-Val-REF) and EE(mag-val-GROUP) for each activity. Furthermore, the mean difference seems to show that the estimation of EE is better with the group equation. In conclusion, on the proven basis of this study we are able to validate this new method which permits the estimation of EE from abdominal and rib cage distances. This study also highlights the advantage of using a group equation to the estimate EE.

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

To validate a new device designed to measure ventilation (V(E)), 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. 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(E), V(T), T(I), and, T(E) measured by magnetometers (V(E)mag, V(T)mag, T(I)mag, and T(E)mag) with V(E), V(T), T(I), and T(E) measured by a spirometer V(E)spiro, V(T)spiro, T(I)spiro, and T(E)spiro, respectively). For pooled data V(E)mag, V(T)mag, T(I)mag, and T(E)mag were significantly correlated (p < 0.001) with V(E)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(E)mag, and V(E)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(E) with reasonable accuracy in sitting, standing, and exercise conditions.

[Maximal respiratory pressures in children: the methodological challenge]. / Pressions respiratoires maximales chez l'enfant: les exigences méthodologiques.

INTRODUCTION: Measurement of maximal respiratory pressures against an occlusion has been used for a long time to assess respiratory muscle strength in the follow up of children with respiratory disease. In the early stage of disease this is the main test for diagnosing respiratory muscle involvement and the degree of that involvement. STATE OF KNOWLEDGES: The interpretation of the results is difficult on account of variability of the measurements and of the reference values. The aim of this article is to present, in the form of a literature review, the normal values available and the different determining factors as well as the advantages and limitations of these measurements. PERSPECTIVES: The use by all the centres undertaking maximal respiratory pressure measurements in children of methodological techniques similar to those presented in this revue could be the starting point for obtaining an identical range of reference values for all. CONCLUSION: Age, sex and the level of physical aptitude seem to be the most important determinants of maximal respiratory pressures. However, other methodological factors such as co-operation, training of the child in the performance of the manoeuvres and the type of device and protocol used, will all influence the results. These factors must be taken into consideration in order to diminish, as much as possible, the variability of the maximal pressures obtained.

[Is it possible to propose the abolition of crutches according to the gait speed in patients with total knee arthroplasty?]. / Peut-on proposer la suppression des cannes anglaises en fonction de la vitesse de marche chez les patients porteurs d'une prothèse totale de genou ?

OBJECTIVE: To determine the stop of crutches to walk in patients with total knee arthroplasty from the test of maximal gait speed. METHOD: 46 patients (73.6 +/- 4.6 years) carried out the maximal gait speed test on a 10-meter track, with two crutches, at the 3rd week after a total knee arthroplasty surgery for gonarthrosis. Two groups were separated according to the need of crutches to walk. Various threshold values of maximal gait speed were then determined (ROC curve) to know if this parameter could define the stop of crutches to walk (Predictive value). RESULTS: Patients able to stop crutches (n = 27) walk faster, than the patients who still need crutches (n = 19), (0.86 +/- 0.17 m/s vs 0.65 +/- 0.14 m/s; p < 0.01). According to the ROC curve, two speeds were chosen: 1.11 m/s (9 s) and 0.55 m/s (18 s). A gait speed superior or equal to 1.11 m/s presents a positive predictive value of 86% to authorize to stop crutches. Below 0.55 m/s, the positive predictive value is 83% to keep crutches. Between these two speeds, the test of maximal gait speed does not help the clinician to decide to stop crutches. CONCLUSION: The test of maximal gait speed brings a help to decide to stop crutches only for speeds superior to 1.11 m/s.

[Ventilatory response to maximal exercise in healthy children]. / La réponse ventilatoire à l'exercice maximal chez l'enfant sain.

INTRODUCTION: The evaluation of the ventilatory response of children during exercise is essential to determine its role in impaired exercise tolerance. The aim of this review is to describe the variables and the values of maximal ventilatory parameters observed in healthy children in the published literature. STATE OF ART: The maximal ventilation (VEmax) and the tidal volume (VTmax) increase in a linear fashion with age and plateau in boys at 15 years, and in girls at 13 years. The main variables for the parameters connected to volume--VEmax and VTmax--are anthropometric characteristics, in particular, the lean body mass. Most studies show a value of 30 ml.kg(-1) for a VTmax on the total body mass in pre-puberty and a slight increase thereafter. The ventilatory reserves and the VTmax on vital capacity increase with age until respective values of 30% and 50% are reached at 17 years. The maximal parameters connected to time are independent of anthropometric characteristics. The TI/TTOT ratio (inspiratory time to total time of the respiratory cycle) is stable with a value of 0.5. The maximal respiratory frequency decreases slightly with age without differences between the genders. PERSPECTIVES AND CONCLUSION: Only studies of larger numbers of children, proposing relationships derived from allometric equations, will be able to provide real reference values.

Diaphragm kinetics during pneumatic belt respiratory assistance: a sonographic study in Duchenne muscular dystrophy.

The principal aim of this study was to demonstrate the usefulness of M-mode sonography as a noninvasive technique to evaluate diaphragm excursion. The secondary aim was to assess the efficacy of pneumatic abdomino-diaphragmatic belt ventilation in patients with Duchenne muscular dystrophy. Using M-mode sonography, we measured the amplitude of diaphragm excursion in seven patients with Duchenne muscular dystrophy in various positions (0 degrees, 45 degrees, 75 degrees ) with and without pneumatic abdomino-diaphragmatic belt respiratory assistance. The belt significantly increased mean amplitude of diaphragm excursion by 62% at 45 degrees and by 55% at 75 degrees, and increased mean tidal volume by 43.5% at 45 degrees and by 49% at 75 degrees. Two patients were unable to tolerate the horizontal position (0 degrees ) During quiet breathing without the belt, amplitude of diaphragm excursion and tidal volume were positively correlated at 45 degrees (r=0.81; P=0.027) and 75 degrees (r=0.75; P=0.05). There was a significant intra-individual correlation between these two parameters during belt use but no inter-individual correlation. Without the belt, thoracic posture had no significant effect on amplitude of diaphragm excursion, either in quiet or deep breathing. After overnight respiratory assistance, arterial oxygen pressure and arterial oxygen saturation increased significantly, and arterial carbon dioxide pressure decreased from 52+/-6.4 to 46.4+/-4 mmHg. The pneumatic abdomino-diaphragmatic belt significantly improved gas exchanges and ventilation by increasing diaphragm excursion, as was clearly shown by noninvasive M-mode sonography. Indeed, M-mode sonography may be helpful in pneumatic abdomino-diaphragmatic belt pressure adjustment.

Physiological profile of handball players.

BACKGROUND: The purpose of this study was to determine the physiological profile of handball players compared to sprinters, endurance trained and untrained subjects. METHODS: Forty-six subjects aged between 19 and 28 years took part in this study: 10 were national handball players (NHB); 7 were international handball players (IHB), 11 were sprint trained subjects (ST); 8 were endurance trained subjects (ET); and 10 were untrained subjects (UT). They performed an incremental treadmill test to determine the maximal oxygen uptake (VO2max), and a Wingate anaerobic test (WanT) to determine maximal power (Wmax). Plasma lactate (La) concentration was measured 5 minutes after the end of the Wingate-test. RESULTS: The VO2max of NHB was similar to that of the IHB and ST athletes but higher than that of the untrained and lower than the endurance trained athletes. Values for Wmax were similar in the IHB and NHB groups and very close to the sprinters. When normalized for body mass or to lean body mass, Wmax was greater in handball players when compared to untrained or endurance trained subjects. Lactate values were in the same range in the NHB, IHB and ST groups and were statistically higher in the NHB and IHB groups than in the UT or ET groups. CONCLUSIONS: The results suggest that the anaerobic metabolism seems to be important for the handball players similarly to sprinters. Since handball is known as a sport with typically short exercise periods of high intensity alternating with rests, anaerobic metabolism appears then to be higbly relevant to performance.

Diaphragm movement before and after cholecystectomy: a sonographic study.

UNLABELLED: Respiratory disorders after abdominal surgery are commonly explained by changes in diaphragmatic movement that are difficult to demonstrate and quantify. Our aim was thus to quantify these changes using a noninvasive method. We used M-mode sonography for the prospective study to measure diaphragmatic amplitude in 14 patients before and after cholecystectomy. During quiet breathing, the diaphragm inspiratory amplitude (DIA) was significantly decreased after surgery from 1.4 +/- 0.2 cm to 1 +/- 0.1 cm and from 1.6 +/- 0.3 cm to 1.2 +/- 0.3 cm in the Laparoscopic and Open Cholecystectomy groups, respectively. The total time cycle of diaphragmatic motion decreased significantly in the two groups. The DIA also decreased significantly during deep breathing after cholecystectomy from 6.0 +/- 0.8 cm to 3.0 +/- 1.8 cm and from 6.1 +/- 1.3 cm to 3.1 +/- 1.6 cm in the Laparoscopic and Open Cholecystectomy groups, respectively. The six patients who underwent spirometric examination showed, during quiet breathing, a significant decrease in DIA without change in tidal volume, i.e., 0.51 +/- 0.08 L to 0.45 +/- 0.08 L. We found a significant decrease in DIA after cholecystectomy and a significant interindividual correlation between DIA during deep inspiration and inspiratory capacity. Using M-mode sonography techniques, we were able to demonstrate changes in diaphragmatic mobility after laparoscopic or open cholecystectomy. IMPLICATIONS: Cholecystectomy at times results in impaired respiratory and diaphragmatic functions. The techniques currently used to study these repercussions are both laborious and invasive. Our sonographic technique is completely noninvasive and can be used to study diaphragm morphology and movement in real time.

[Maximal oxygen uptake in healthy children: factors of variation and available standards]. / La consommation maximale d'oxygène chez l'enfant sain: facteurs de variation et normes disponibles.

Aerobic physical fitness, in children, is assessed by measurement of the maximal oxygen consumption during exercise testing. Representative norms of the studied population are required for interpretation. The aim of this article is to specify and review the available VO2max norms and factors of variation, including: sex, anthropometric characteristics (height, lean body mass and weight) and physical activity level. Ideally, VO2max norms should include lean body mass and physical activity with an allometric equation. Since such norms do not exist today, interpretation remains difficult. In France, the must satisfactory norms for non trained children include body mass without an allometric equation (boys: 47 +/- 2 ml.mn.-1 kg-1, girls: 40 +/- 3 ml.mn.-1 kg-1 with a post puberty decrease). Further studies on VO2max norms that include lean body mass and a physical activity questionnaire are required to improve exercise test interpretation in children.

Effect of ageing on the ventilatory response and lactate kinetics during incremental exercise in man.

We investigated the effects of age on breathing pattern, mouth occlusion pressure, the ratio of mouth occlusion pressure to mean inspiratory flow, and venous blood lactate kinetics during incremental exercise. Mouth occlusion pressure was used as an index of inspiratory neuromuscular activity, and its ratio to mean inspiratory flow was used as an index of the "effective impedance" of the respiratory system. Nine elderly male subjects [mean (SD) age: 68.1 (4.8) years] and nine young male subjects [mean (SD) age: 23.4 (1.3) years] performed an incremental exercise test on a bicycle ergometer. After a warm-up at 30 W, the power was increased by 30 W every 1.5 min until exhaustion. Our results showed that at maximal exercise, power output, breathing pattern, and respiratory exchange values, with the exception of tidal volume and the "effective impedance" of the respiratory system, were significantly higher in the young subjects. The power output and oxygen consumption values at the anaerobic threshold were also significantly higher in the young men. At the same power output, the elderly subjects showed significantly higher values for minute ventilation, respiratory equivalents for oxygen uptake and carbon dioxide output (CO(2)), mean inspiratory flow, occlusion pressure and lactate concentration than the young subjects. At the same CO(2) below the anaerobic threshold (0.5, 0.75, 1.00 and 1.25 l x min(-1)), minute ventilation and lactate concentration were also significantly higher in the elderly subjects. We observed a significantly higher minute ventilation at CO(2) values of 0.5, 0.75, 1.00 (P < 0.001) and 1.25 l x min(-1) (P < 0.05) in the elderly men, and a significantly higher lactate concentration at CO(2) values of 1.00 (P < 0.05) and 1.25 l x min(-1) (P < 0.01). In conclusion, the ventilatory response in elderly subjects is elevated in comparison with that in young subjects, both below and above the anaerobic threshold. This study demonstrates for the first time that this ventilatory increase, both below and above the threshold, is partly due to an increased lactate concentration.

Ventilation response to CO2 and exercise-induced hypoxaemia in master athletes.

Exercise-induced hypoxaemia (EIH) in master athletes may be related to a diminished exercise hyperpnoea. The aim of this study was to determine whether EIH is associated with a change in the sensitivity of the ventilation response to activation of the central chemoreceptors. The ventilation response to CO2 was measured in nine elderly untrained men (UT) [mean age 66.3 (SEM 3.1) years] and nine master athletes (MA) [mean age 62.7 (SEM 0.8) years] at rest, during moderate exercise (40% maximal oxygen uptake, VO2max), and during strenuous exercise (70% VO2max) using the rebreathing method. Our results showed that the ventilation response to CO2 did not differ with endurance training and/or exercise, that the threshold of the CO2 response (Th) increased with exercise (P < 0.001), that the increase in Th in MA was higher than in UT between rest and moderate exercise [deltaTh(0-40): 8.55 (SEM 1.8) vs 3.06 (SEM 1.72) mmHg, P < 0.05], and that deltaTh(0-40) and Th during moderate exercise were negatively correlated with arterial O2 saturation during maximal exercise (r=0.50, P

Effect of step duration during incremental exercise on breathing pattern and mouth occlusion pressure.

We compared the effects of two step durations on breathing pattern, mouth occlusion pressure and "effective" impedance of the respiratory system during incremental exercise. Nine normal subjects (mean age: 27.8+/-1.21 years) performed two incremental exercise tests in randomized order: one test with step increments every 1 min 30s and the other, every 4 min. After a warm-up at 25 W for the 1 min 30 s test, the power was increased by 50 W from 50 W to exhaustion. During the last minute at each power, we measured ventilation (VE), tidal volume (VT), breathing frequency (fR), inspiratory and expiratory time (TI and TE), total time of the respiratory cycle (TTOT), TI/TTOT, mean inspiratory flow (VT/TI), mouth occlusion pressure (P0.1), "effective" impedance of the respiratory system (P0.1/(VT/ TI)) and venous blood lactate concentration ([La]). Our result showed that at maximal exercise the power was significantly higher (p < 0.01) and [La] lower (p < 0.01) in the 1 min 30 s test. At 100, 150 and 200 W, the 4 min test showed significantly higher oxygen uptake (VO2), carbon dioxide output (VCO2), VE, P0.1, fR, VT/TI and HR (p <0.001) and significantly lower TI, TE and TTOT (p<0.01). [La] was significantly higher at 150 W (p<0.05) and 200 W (p<0.001). At the same VCO2, P0.1 was not significantly different between the two tests, whereas VE showed a tendency to be higher (p = 0.08) and P0.1/(VT/TI) was significantly lower during the 4 min test. In conclusion, this study allowed us to quantify the difference in inspiratory neuromuscular output and ventilatory response between 1 min 30s and 4 min tests and showed that different step durations alter the relationship between inspiratory neuromuscular output and mean inspiratory flow.

Changes in maximal exercise ventilation and breathing pattern in boys during growth: a mixed cross-sectional longitudinal study.

The aim of this mixed cross-sectional longitudinal study covering a total age range of 11-17 years, i.e. the entire pubertal growth period, was (1) to specify the changes in maximal breathing pattern during incremental exercise; (2) to determine what parts of the changes are due to anthropometric characteristics, physical fitness and inspiratory or expiratory muscle strength; and (3) to determine if the role of these variables is identical before, during and after pubertal growth spurt. This study was conducted in 44 untrained schoolboys separated into three groups, with an initial age of 11.2 +/- 0.2 years for group A, 12.9 +/- 0.25 years for group B, and 14.9 +/- 0.26 years for group C. These children were subsequently followed for 3 years, during the same time period each year. The maximal inspiratory and expiratory pressures (PI max and PE max) were used as an index of the respiratory muscle strength. During an incremental exercise test, maximal ventilation (VE max), tidal volume (VT max), breathing frequency (fmax), inspiratory and expiratory times (tI max and tE max) and mean inspiratory flow (VT/tI max) were measured at maximal oxygen uptake (VO2max). Our study showed that there was a marked increase with age in VE max, VT max, and VT/tI max, and no significant changes in fmax, tI max and tE max. PI max and PE max showed a general trend towards an increase between 11 and 17 years. The study of the linear correlations between maximal breathing pattern and the anthropometric characteristics, physical fitness and inspiratory or expiratory muscle strength showed that, in the three groups of children, (1) lean body mass was the major determinant of VE max, VT max and VT/tI max and the relationships were significantly different before, during and after the pubertal growth spurt; (2) physical fitness was the main determinant of tI max, tE max and fmax before and after the pubertal growth spurt; and (3) maximal respiratory strength did not play a significant role. In conclusion, this mixed cross-sectional longitudinal study showed, at maximal exercise, a significant increase in VE max during growth due only to a significant increase in VT max and VT/tI max, and that the relationships of anthropometric characteristics and physical fitness with maximal breathing pattern change during growth.

Differences in mouth occlusion pressure and breathing pattern between arm and leg incremental exercise.

The aim of the study was to compare breathing pattern, mouth occlusion pressure, mean inspiratory flow and the ratio of mouth occlusion pressure to mean inspiratory flow at the same power output and carbon dioxide output during arm and leg incremental exercise. Mouth occlusion pressure was used as an index of inspiratory neuromuscular activity and its ratio to mean inspiratory flow as an index of the 'effective' impedance of the respiratory system. Eight normal subjects performed two incremental exercise tests, one with arms, the other with legs, on different weeks and in randomized order, and on two identical cycle ergometers. The power output was increased by steps of 25 W for arms and 50 W for legs every 4 min until exhaustion. At the same power output, oxygen consumption, carbon dioxide output, ventilation, mean inspiratory flow, mouth occlusion pressure, 'effective' impedance (P < 0.001) and respiratory frequency (P < 0.01) were higher during arm exercise than during leg exercise, whereas inspiratory time (P < 0.05) and expiratory time (P < 0.01) were lower. At the same carbon dioxide output, mouth occlusion pressure, ventilation, 'effective' impedance (P < 0.001) and respiratory frequency (P < 0.01) were higher and expiratory time (P < 0.05) was lower during arm exercise. In conclusion, the higher inspiratory neuromuscular activity and impedance of the respiratory system during arm exercise and the differences observed in ventilation and breathing pattern at equal carbon dioxide output seem related to the differences in exercising muscle afferents and the presence of an increased load due to contraction of rib cage muscles to stabilize posture.

[Evolution of breathing pattern and ventilation at maximal exercise during growth. Definition of reference values]. / Evolution du régime ventilatoire et de la ventilation à l'exercice maximal en période de croissance. Définition de valeurs de références.

The aim of the study was to define the changes of parameters of breathing pattern and ventilation (VE) as a function of age during maximal exercise in children. A multi-longitudinal survey was conducted in forty four untrained schoolboys, divided in three groups with initial age of 11.2 years for group I, 12.9 years for group II, and 14.9 for group III. These children were subsequently followed three years ago at the same period. The range age was thus 11.2 to 16.9 years. This study showed that, during growth, ventilation (VE max), tidal volume (VT max) and mean inspiratory flow (VT/TI max) increased significantly with age, that inspiratory frequency (f max) decreased, that inspiratory, expiratory and total time of the respiratory cycle (TI max, TE max, TTOT max) increased slightly and that the inspiration fraction (TI/TTOT max) was identical at 11 and 17 years. Furthermore we observed that the peak height velocity and peak tidal volume velocity took place at the same age, i.e., 14 years and that those of weight and VT/TI at the same age of 15 years. In conclusion, this study allowed us to define reference values for breathing pattern at maximal exercise in sedentary boys and to specify the relation between growth and parameters of breathing pattern in these children.