Biomedical subjects

S Matecki

Publications and source records attributed to S Matecki.

12 recordsLinked to original sources

PubMed2005

Effect of inspiratory threshold loading on ventilatory kinetics during constant-load exercise.

Humoral factors play an important role in the control of exercise hyperpnea. The role of neuromechanical ventilatory factors, however, is still being investigated. We tested the hypothesis that the afferents of the thoracopulmonary system, and consequently of the neuromechanical ventilatory loop, have an influence on the kinetics of oxygen consumption (VO2), carbon dioxide output (VCO2), and ventilation (VE) during moderate intensity exercise. We did this by comparing the ventilatory time constants (tau) of exercise with and without an inspiratory load. Fourteen healthy, trained men (age 22.6 +/- 3.2 yr) performed a continuous incremental cycle exercise test to determine maximal oxygen uptake (VO2max = 55.2 +/- 5.8 ml x min(-1) x kg(-1)). On another day, after unloaded warm-up they performed randomized constant-load tests at 40% of their VO2max for 8 min, one with and the other without an inspiratory threshold load of 15 cmH2O. Ventilatory variables were obtained breath by breath. Phase 2 ventilatory kinetics (VO2, VCO2, and VE) could be described in all cases by a monoexponential function. The bootstrap method revealed small coefficients of variation for the model parameters, indicating an accurate determination for all parameters. Paired Student's t-tests showed that the addition of the inspiratory resistance significantly increased the tau during phase 2 of VO2 (43.1 +/- 8.6 vs. 60.9 +/- 14.1 s; P < 0.001), VCO2 (60.3 +/- 17.6 vs. 84.5 +/- 18.1 s; P < 0.001) and VE (59.4 +/- 16.1 vs. 85.9 +/- 17.1 s; P < 0.001). The average rise in tau was 41.3% for VO2, 40.1% for VCO2, and 44.6% for VE. The tau changes indicated that neuromechanical ventilatory factors play a role in the ventilatory response to moderate exercise.

Adult↗

PubMed2004

[Maximal respiratory pressures in children: the methodological challenge].

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.

Child↗

PubMed2003

Effect of food restriction on lactate sarcolemmal transport.

The objective of this study was to investigate the effects of 6 weeks of food restriction (FR) on sarcolemmal lactate transport in rats. The daily food consumption of rats was monitored for 10 days, after which they were assigned to either a control group (CTL, n = 7) that consumed food ad libitum or an FR group (n = 7) that received a daily ration equal to 60% of their predetermined baseline food intake. After the 6-week period, we observed in red gastrocnemius (RG) a fall of 48% in glycogen content (P <.01) and a reduction in glutathione peroxidase activity (P <.05), confirming that the FR program was well executed. FR resulted in a reduction in muscle lactate (P <.05) and liver glycogen contents (P <.01). Moreover, hyperlactatemia was noted in the FR group: 1.77 +/- 0.24 versus 2.67 +/- 0.29 mmol/L (P <.05). Lactate transport capacity was significantly increased (P <.05) in FR rats, although monocarboxylate transporter isoforms (MCT1 and MCT4) did not change significantly. We conclude that FR alters sarcolemmal lactate transport activity without affecting MCT1 and MCT4 expression.

Animals↗

PubMed2003

The effects of prior cycling and a successive run on respiratory muscle performance in triathletes.

The aim of the present study was to compare the effects of prior cycling and a successive run on respiratory muscle performance during a cycle-run succession as performed in the triathlon. We hypothesized that despite the moderate intensity of exercise and the absence of exhaustion, the crouched cycling position would induce a decrease in respiratory muscle performance that would be reversed by the successive vertical run position. Ten male triathletes (22.6 +/- 1.1 yr) performed a four-trial protocol: (1) an incremental cycle test to assess maximal oxygen uptake (VO2max), (2) 20 min of cycling (C), (3) 20 min of running (R), and (4) 20 min of cycling followed by 20 min of running (C-R). Trials 2, 3 and 4 were performed at the same metabolic intensity, i. e., 75 % of VO2max. Respiratory muscle force was assessed by measuring maximal expiratory (P(Emax)) and inspiratory (P(Imax)) pressures from the functional residual capacity (FRC) before and 10 min after C, R, and C-R. Respiratory muscle endurance was assessed one day before and 30 min after C, R, and C-R, by measuring the time limit (T(lim)), which corresponds to the length of time a respiratory load can be sustained before the process of fatigue develops sufficiently to cause task failure. The results showed a similar significant decrease in P(Imax) (132.4 +/- 4.9 versus 125.7 +/- 5.6 cm H2O, p < 0.05) and T(lim) (5.22 +/- 0.28 versus 3.68 +/- 0.32 min, p < 0.05) post-C and post-C-R (133.7 +/- 4.0 versus 126.9 +/- 5.2 cm H2O, and 5.29 +/- 0.18 versus 3.49 +/- 0.41 min, respectively, p < 0.05) compared with the pre-trial values. In contrast, P(Imax) and T(lim) were not significantly decreased post-R (131.8 +/- 6.1 cm H2O versus 129.6 +/- 6.4 cm H2O, and 4.90 +/- 0.69 versus 4.40 +/- 0.56 min, respectively, p > 0.05). We concluded that moderate intensity exercise not performed to exhaustion induced a decrease in respiratory muscle performance. Moreover, the respiratory muscle fatigue induced by prior cycling was maintained, and neither reversed nor worsened, by the successive run.

Adaptation, Physiological↗

PubMed2003

[Ventilatory response to maximal exercise in healthy children].

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.

Child↗

PubMed2002

The effect of cycling followed by running on respiratory muscle performance in elite and competition triathletes.

This study investigated the possibility of there being differences in respiratory muscle strength and endurance in elite and competition triathletes who have similar maximal oxygen uptakes (VO(2max)) and ventilatory thresholds (Th(vent)). Five internationally-ranked elite, [mean (SD) age 23.8 (1.4) years] and six nationally- and regionally-ranked competition [age 21.1 (1.1) years] male triathletes performed two successive trials: first an incremental cycle test to assess VO(2max) and Th(vent) and second 20 min of cycling followed by 20 min of running (C-R) at intensities higher than 85% VO(2max). Cardioventilatory data were collected every minute during the two trials, using an automated breath-by-breath system. Maximal expiratory and inspiratory (P(Imax)) strength were assessed before and 10 min after C-R from the functional residual capacity. Respiratory muscle endurance was assessed 1 day before and 30 min after C-R by measuring the time limit (t(lim)). The results showed firstly that during C-R, the competition triathletes had significantly (P < 0.05) higher minute ventilation [mean (SEM) 107.4 (3.1) compared to 99.8 (3.7) l x min(-1)], breathing frequency [44.4 (2.0) compared to 40.2 (3.4) x min(-1)] and heart rate [166 (3) compared to 159 (4) beats x min(-1)] and secondly that after C-R, they had significantly lower P(Imax) [127.1 (4.2) compared to 130.7 (3.0) cmH(2)O] and t(lim) [2:35 (0:29) compared to 4:12 (0:20) min] than the elite triathletes. We conclude that, despite similar VO(2max) and Th(vent), the competition triathletes showed less extensive adaptive mechanisms, including those in the respiratory muscles, than did the elite triathletes. This led to higher ventilation, which appeared to be the cause of the faster development of fatigue in the inspiratory muscles in this group.

Adult↗

PubMed2001

A standardized method for the evaluation of respiratory muscle endurance in patients with Duchenne muscular dystrophy.

The aim of the study was to develop a standardized method using controlled breathing to quantify respiratory muscle endurance in children with Duchenne muscular dystrophy (DMD) and to test its reproducibility. In 10 DMD patients, all between 10 and 14 years (mean age, 11.5 +/- 1.5 years), except for two patients of 20 and 22 years, and 10 healthy children (mean age, 12 +/- 1 years), we measured the maximal time (Tlim) that a threshold load fixed at 35% of the individual maximal inspiratory pressure (Pimax) could be tolerated. We asked the children to maintain their rest breathing pattern until exhaustion using visual feedback and an auditory signal. The mean Tlim in the DMD children was 4.45 +/- 1.45 min and values were reproducible. All healthy children were able to obtain Tlim values greater than 30 min. The respiratory muscles of DMD children are more susceptible to fatigue than those of healthy subjects. This method should be satisfactory for estimating the effect of treatment and for the specific training of respiratory muscles in DMD patients without significant learning disability.

Adolescent↗

PubMed2001

The effect of exercise modality on respiratory muscle performance in triathletes.

PURPOSE: The aim of this study was to examine the effects of the cycle-run and run-cycle successions of the triathlon and duathlon, respectively, on respiratory muscle strength and endurance. METHODS: Respiratory muscle strength was assessed by measuring maximal inspiratory (P(Imax)) and expiratory (P(Emax)) pressures. Respiratory muscle endurance was assessed by measuring the time limit (T(lim)). Twelve triathletes participated in a three-trial protocol. The first trial consisted of an incremental cycle test to assess the maximal oxygen uptake (.VO(2max)) of triathletes. Trial 2 consisted of 20 min of cycling followed by 20 min of running (C-R), and trial 3 consisted of 20 min of running followed by 20 min of cycling (R-C). Trials 2 and 3 were performed at the same metabolic intensity (%.VO(2max)). P(Imax) and P(Emax) were measured before and 10 min after C-R and R-C, and 1 min after the post-C-R and post-R-C T(lim) measurements (P(Imax) 1'). T(lim) was measured 1 d before and 30 min after C-R and R-C. RESULTS: The results showed a significant decrease in P(Imax) after C-R (126.7 +/- 4.3 cmH(2)O, P < 0.05) and R-C (123.7 +/- 4.9 cmH(2)O, P < 0.05) compared with the baseline values (130 +/- 3.8 and 129.6 +/- 4.3 cmH(2)O, respectively). P(Imax) 1' showed a significantly greater decrease after R-C versus C-R (111.2 +/- 5.5 cmH(2)O vs 121.2 +/- 3.9 cmH(2O), respectively, P < 0.001). Tlim after C-R (3.3 +/- 0.3 min) and R-C (2.1 +/- 0.3 min) decreased significantly compared with baseline values (4.19 +/- 0.3 min and 4.02 +/- 0.3 min, respectively). However, the Tlim decrease after R-C was significantly greater than after C-R (P < 0.001). CONCLUSION: We concluded that respiratory muscle strength and endurance were less decreased after the cycle-run succession and that cycling induced a greater decrease in respiratory muscle endurance than running.

Adult↗

PubMed2001

[Indications and application of exercise tests in children].

Exercise tests are routinely used in children to assess cardio-respiratory and muscular adaptations to exercise. However these tests are of relatively recent use, and there is a lack of standardization and of relevant data in large groups in this population. The aim of this paper was to specify the common medical indications of exercise tests in children, to propose standardized protocols of these tests in some of the most common pathological situations as: exercise-induced asthma, chronic respiratory diseases (bronchopulmonary dysplasia, cystic fibrosis), muscular diseases. These tests can provide clinically relevant parameters only when they are used in strict conditions of standardization.

Child↗

PubMed2001

[Maximal oxygen uptake in healthy children: factors of variation and available standards].

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.

Body Height↗

PubMed2000

Noninvasive assessment of inspiratory muscle function during exercise.

The use of esophageal and gastric balloons limits measurement of the tension-time index of inspiratory muscles (TTI) during exercise. The aim of this study was to assess whether a noninvasive tension-time index, TT(0.1), given by P(0.1)/PI(max) x TI/Ttot (where P(0.1) is mouth occlusion pressure, PI(max) is maximal inspiratory pressure, and TI/Ttot is duty cycle) could reliably assess TTI during exercise. In seven healthy young men and nine patients with COPD we measured TT(0.1) and TTI (i.e., Pes/Pes(max) x TI/Ttot where Pes is mean esophageal pressure and Pes(max) is maximal static Pes) at rest and during an incremental exercise test. A significant linear correlation (p < 0.02) was found between TT(0.1) and TTI in all normal subjects and patients with COPD. An equation for estimating TTI from TT(0.1) was established for each group. In the normal subjects there was good agreement between estimated and observed data. In five additional normal males studied prospectively, the agreement was also satisfactory and reproducible. In the COPD patients the agreement was poor. In conclusion, in young healthy subjects the changes in TT(0.1) during exercise reflect the changes in TTI, allowing satisfactory estimation of TTI from noninvasive measurements of TT(0.1).

Adult↗

PubMed1999

Effects of erythropoietin administration in training athletes and possible indirect detection in doping control.

PURPOSE: This study investigated the effects of repeated subcutaneous injection of rHuEpo (50 IU x kg(-1)) in athletes and proposes a method based on the measurement in blood samples of the sTfR/serum protein ratio to determine if the observed values of this marker are related to rHuEpo abuse. METHODS: Serum erythropoietin concentrations, and hematological and biochemical parameters were evaluated, during treatment and for 25 d posttreatment in nine training athletes. Moreover, the effect of rHuEpo administrations on the maximum oxygen uptake (VO2max) and ventilatory threshold (VT) of these athletes was also studied. Threshold values for sTfr and the sTfr/serum protein ratio were determined from 233 subjects (185 athletes, 15 athletes training at moderately high altitude, and 33 subjects living at >3000 m). RESULTS: Significant changes in reticulocytes, hemoglobin (Hb) concentration, hematocrit (Hct), sTfr, and sTfr/serum proteins were observed during and after rHuEpo treatment. The maximal heart rate of 177 beats x min(-1) at the beginning of the study was significantly higher than the value of 168 beats x min(-1) after 26 d of rHuEpo administration. Compared with the values measured at baseline, the VT measured after rHuEpo administration occurred at a statistically significant high level of oxygen uptake. CONCLUSIONS: When oxygen uptake measured at the VT was expressed as a percentage of V02 max, the values obtained were also significantly higher. The increased values of Tfr and sTfr/serum proteins, respectively, above 10 microg x mL(-1) and 153, indicated the probable intake of rHuEpo.

Adult↗