Biomedical subjects

C Préfaut

Publications and source records attributed to C Préfaut.

At least 91 records · Page 5Linked to original sources

PubMed1995

[Right diaphragmatic kinetics measured by TM-mode ultrasonography with concomitant spirometry in normal subjects and asthmatic patients. Preliminary results].

The purpose of this study was to assess the diaphragmatic excursion using the TM-mode ultrasonography with concomitant pneumotachography in eight normal and five asthmatic subjects before and after salbutamol. We report the results in normal and asthmatic patients of this procedure. Particular findings were demonstrated in asthma. Different significant correlations were found between sonographic and respiratory measurements. In view of the safety of this direct and real-time diaphragmatic investigation, we conclude that this new method could offer an effective and reliable procedure in the evaluation of patients with diaphragmatic dysfunction. However, our study was limited by the small number of patients included and definite conclusions should await further investigations.

Adrenergic beta-Agonists↗

PubMed1995

Exercise intolerance in patients with chronic heart failure: role of pulmonary diffusing limitation.

In order to test the hypothesis of pulmonary diffusing capacity involvement in exercise limitation in subjects with chronic heart failure (CHF), lung transfer factor (TLCO), oxygen saturation (SaO2), cardiac output (CO) and gas exchange were studied over the course of an incremental exercise test in 10 patients and 10 controls. The TLCO and transfer coefficient for carbon monoxide (TLCO/VA) were measured at rest and during recovery by the single breath method. The SaO2 was followed non-invasively with a finger oximeter and CO was determined according to the carbon dioxide rebreathing method. Analysis of respiratory variables at maximal effort showed significantly lower values in patients with CHF as regards peak oxygen uptake (VO2), minute ventilation (VE), heart rate (HR), oxygen pulse (O2 pulse), and CO with higher ventilatory reserve (VR) than controls. At a comparable workload (30 W), patients with CHF demonstrated higher values for VE and lower values for CO than controls. The TLCO, expressed as percent of predicted values, was significantly lower in CHF patients than controls, respectively, at rest (90.5 +/- 3.75% vs 106.8 +/- 3.8%) and within 5 min after maximal exercise (87 +/- 4.4% vs 117.4 +/- 3.81%). The TLCO/VA showed comparable data between the two groups at rest (81.7 +/- 3.28 vs 90.3 +/- 2.86%). However, significantly lower values of TLCO/VA were obtained for CHF after maximal exercise in comparison to control subjects (77.5 +/- 3.85% vs 96.3 +/- 3.95%). These results confirm the alteration of the main variables in relation to cardiopulmonary exercise limitation in-tHF, and indicate a significant decrease in TLCO and TLCO/VA after maximal exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise↗

PubMed1995

Validation of a noninvasive tension-time index of inspiratory muscles.

The aim of this study was to validate a noninvasive tension-time index (TT) for all the inspiratory muscles estimated from the measurement of mouth occlusion pressure (P0.1), i.e., TT of inspiratory muscles (TTmus = PI/PImax x TI/TT, where PI is mean inspiratory pressure, PImax is maximal PI, TI is time of muscle contraction, and TT is total time of respiratory cycle) compared with TT of the diaphragm (TTdi = Pdi/Pdimax x TI/TT, where Pdi is mean transdiaphragmatic pressure and Pdimax is maximal Pdi). PI was estimated as PI = 5 P0.1 x TI. Eleven patients with chronic obstructive pulmonary disease and seven normal subjects were studied at rest in the sitting position. After 5 min of steady state, we measured breathing pattern, gastric and esophageal pressures, Pdi, mean inspiratory transpulmonary pressure swing, PImax, and Pdimax. By linear regression analysis, significant positive correlations were found between PI and mean inspiratory transpulmonary pressure swing, PI and Pdi, PImax and Pdimax, and PI/PImax and Pdi/Pdimax, with P < 0.001 for all subjects combined. These led to the highly significant correlation between TTmus and TTdi for all subjects combined (TTmus = 2.1 TTdi + 0.012; r = 0.97; P < 0.001) and for patients only (TTmus = 2.0 TTdi + 0.024; r = 0.97; P < 0.001). Therefore, patterns of breathing that lie near fatigue thresholds can be identified with TTmus or TTdi. In conclusion, noninvasive and clinically easily determined TTmus seems valid for situating patients of chronic obstructive pulmonary disease in reference to the inspiratory muscle fatigue.

Aged↗

PubMed1995

Computerized tomography and pulmonary diffusing capacity in highly trained athletes after performing a triathlon.

We investigated the computerized tomographies (CTs) of the thorax and the pulmonary diffusing capacity for CO (DLCO) in eight male athletes before and after a triathlon. DLCO and alveolar volume (VA) were simultaneously measured during 9 s of breath holding. The transfer coefficient (KCO = DLCO/VA) was then calculated. CT scanning was performed during breath holding with the subjects in the supine position. Scanner analysis was done by 1) counting the linear and polygonal opacities (index of interstitial fluid accumulation) and 2) calculating the physical mean lung density and the mean slice mass. Results showed a significant reduction in DLCO (44.9 +/- 2.3 vs. 42.9 +/- 1.7 ml.min-1.mmHg-1; P < 0.05) and KCO (6.0 +/- 0.3 vs. 5.6 +/- 0.3 ml.min-1.mmHg-1.l of VA-1; P < 0.05) after the triathlon and an increase in mean lung density (0.21 +/- 0.009 vs. 0.25 +/- 0.01 g/cm3; P < 0.0001). The number of polygonal and linear opacities increased after the race (P < 0.001). This study confirmed that DLCO and KCO decrease in elite athletes after a long-distance race and showed a concomitant increase in CT lung density and in the number of opacities.

Adult↗

PubMed1995

[Physical activity and cardiorespiratory equilibrium].

Nowadays it is believed that each patient can participate in a physical activity adapted to his or her pathology, based on a rationale. In cardiorespiratory patients, the crucial point is an excessive hyperventilation at submaximal exercise. The "dyspnea spiral" is a good model for understanding this particular response. The lung and cardiac function impairment induces dyspnea during moderate exercise. To avoid this dyspnea, the patient develops a sedentary lifestyle which induces deconditioning, i.e., regression of the aerobic pathway. For a given load, anaerobic glycolysis plays an increasingly important role. This leads to an increase in blood lactate concentration during exercise. The buffering of lactic acidosis by blood bicarbonate produces an additional amount of CO2, and results in a proportional increase in ventilation requirement, which increases dyspnea. The patient again decreases his physical activity, and the downward spiral continues. Thus in cardiorespiratory patients dyspnea has two origins. The primary disease is the heart or lung disease. The deconditioning is a true secondary disease. The aim of exercise training in cardiorespiratory patients is to treat secondary disease in order to relieve dyspnea, and increase exercise tolerance and therefore quality of life. Training sessions usually last 45 minutes, two or three times a week, at the intensity of anaerobic threshold, this latter being more precise and individualized than an arbitrary percentage of maximal heart rate. The results show a decrease in ventilation at submaximal level of exercise up to 20-30% with a systematic alleviation of dyspnea and an increase in exercise tolerance and in quality of life. Exercise training in considered to be the best treatment of dyspnea in cardiorespiratory patients.

Adaptation, Physiological↗

PubMed1994

Energy expenditure and cardiorespiratory responses at the transition between walking and running.

We investigated whether the spontaneous transition between walking and running during moving with increasing speed corresponds to the speed at which walking becomes less economical than running. Seven active male subjects [mean age, 23.7 (SEM 0.7) years, mean maximal oxygen uptake (VO2max), 57.5 (SEM 3.3) ml.kg-1.min-1, mean ventilatory threshold (VTh), 37.5 (SEM3) ml.kg-1.min-1] participated in this study. Each subject performed four exercise tests separated by 1-week intervals: test 1, VO2max and VTh were determined; test 2, the speed at which the transition between walking and running spontaneously occurs (ST) during increasing speed (increases of 0.5 km.h-1 every 4 min from 5 km.h-1) was determined; test 3, the subjects were constrained to walk for 4 min at ST, at ST +/- 0.5 km.h-1 and at ST +/- 1 km.h-1; and test 4, the subjects were constrained to run for 4 min at ST, at ST +/- 0.5 km.h-1 and at ST +/- 1 km.h-1. During exercise oxygen uptake (VO2), heart rate (HR), ventilation (VE), ventilatory equivalents for oxygen and carbon dioxide (VE/VO2, VE/VCO2), respiratory exchange ratio (R), stride length (SL), and stride frequency (SF) were measured.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

Effects of 2-chloropropionate on venous plasma lactate concentration and anaerobic power during periods of incremental intensive exercise in humans.

We investigated the effects of a stimulation of pyruvate dehydrogenase (PDH) activity induced by 2-chloropropionate (2-CP) on venous plasma lactate concentration and peak anaerobic power (W an, peak) during periods (6 s) of incremental intense exercise, i.e. a force-velocity (F-v) test known to induce a marked accumulation of lactate in the blood. The F-v test was performed twice by six subjects according to a double-blind randomized crossover protocol: once with placebo and once with 2-CP (43 mg.kg-1 body mass). Blood samples were taken at ingestion of the drug, at 10, 20, and 40 min into the pretest period, at the end of each period of intense exercise, at the end of each 5-min recovery period, and after completion of the F-v test at 5, 10, 15, and 30 min. During the F-v test, venous plasma lactate concentrations with both placebo and 2-CP increased significantly when measured at the end of each period of intense exercise (F = 33.5, P < 0.001), and each 5-min recovery period (F = 24.6, P < 0.001). Venous plasma lactate concentrations were significantly lower with 2-CP at the end of each recovery period (P < 0.01), especially for high braking forces, i.e. 8 kg (P < 0.05), 9 kg (P < 0.02), and maximal braking force (P < 0.05). After completion of the F-v test, venous plasma lactate concentrations were also significantly lower with 2-CP (P < 0.001). The percentage of lactate decrease between 5- and 30-min recovery was significantly higher with 2-CP than with the placebo [59 (SEM 4)% vs 44.6 (SEM 5.5)%, P < 0.05]. Furthermore, W an, peak was significantly higher with 2-CP than with the placebo [1016 (SEM 60) W vs 957 (SEM 55) W, P < 0.05]. In conclusion, PDH activation by 2-CP attenuated the increase in venous plasma lactate concentration during the F-v test. Ingestion of 2-CP led to an increased W an, peak.

Adult↗

PubMed1994

Release of cytokines by blood monocytes during strenuous exercise.

During strenuous exercise in endurance athletes, monocytes are activated and there is an acute inflammation and hypoxemia possibly due to lesional pulmonary edema. IL-6 and TNF-alpha released by monocytes may be implicated in the acute phase of lesional pulmonary edema. A study was carried out to determine whether TNF-alpha and IL-6 are released during strenuous exercise, and, if adrenalin released during exercise alters their generation. Ten young and six master athletes underwent an incremental exercise test. Arterial blood was drawn at rest, at the end of the exercise, and 20 minutes afterwards. Monocytes were isolated and incubated for 18 hours in the presence or absence of adrenalin. Il-6 and TNF-alpha were measured in monocyte supernatants. The spontaneous release of IL-6 or TNF-alpha was increased in young athletes when compared to older subjects. The spontaneous release of TNF-alpha was increased, but not significantly, by exercise and there was no correlation between the release of IL-6 and TNF-alpha and lung function measured during hypoxemia. Adrenalin inhibited the release of IL-6 or TNF-alpha. Correlations were observed between the in vitro release of IL-6 or TNF-alpha and age, VO2max, maximal ventilation and maximal power output of the subjects.

Adult↗

PubMed1994

Exercise-induced hypoxemia in older athletes.

To determine whether exercise induces hypoxemia in highly trained older "master" athletes (MA), as it does in certain elite endurance-trained young athletes (YA), 10 MA (65.3 +/- 2.6 yr), 10 control subjects (CS; 68.3 +/- 2.2 yr), and 10 endurance-trained YA (23.3 +/- 1.1 yr) performed an incremental exercise test. During testing, blood samples for arterial blood gas analysis were drawn during the last 20 s of each load. Lung exchanges were measured using a breath-by-breath automated exercise device. Exercise-induced hypoxemia (EIH) appeared in all MA and 8 of 10 YA, whereas there were no changes in the blood gases of CS. In MA, arterial PO2 decreased significantly from 40% of maximal O2 uptake onward and was associated with a significant increase in the ideal alveolar-arterial O2 difference from 60% onward. The MA also showed a lower ventilation for a given absolute load compared with CS. In all subjects arterial PCO2 rose slightly but significantly during the work, but this increase was most marked in MA. The EIH differed between MA and YA in the following ways: 1) all MA showed a drop in arterial PO2 during exercise, 2) this drop appeared earlier and was significantly greater for a given load in MA, and 3) EIH appeared at a lower level of training regimen in MA. This hypoxemia was at first isolated, probably at least partially due to relative hypoventilation, and then was associated with a widened ideal alveolar-arterial O2 difference, which may have been due to an increase in extravascular lung water.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

Histamine and exercise-induced hypoxemia in highly trained athletes.

To determine whether exercise-induced hypoxemia in extreme athletes results from an increase in histamine level during maximal incremental exercise, seven young athletes [YA; age 22.2 +/- 1.23 (SE) yr] and seven master athletes (MA; age 66.2 +/- 2.94 yr), all of whom were known to develop exercise-induced hypoxemia, were compared with age-matched control groups (young controls and older controls, respectively). During maximal incremental exercise, blood samples for arterial blood gas analysis and for plasma and total histamine were drawn at rest and at 50, 75, and 100% of maximal O2 uptake. The percentage of histamine released (%H) was calculated from plasma and total histamine samples. In all athletes (MA and YA groups), exercise induced an increase in %H with a concomitant decrease in arterial PO2 (PaO2); in control groups there was no change in either histamine levels or PaO2. When the data for the YA and MA groups were combined, a correlation was observed between the increase in %H and the drop in PaO2. Nevertheless, further studies are required to establish whether histamine plays a causative role in hypoxemia or is a response to injury.

Adult↗

PubMed1994

[Value of individualized rehabilitation at the ventilatory threshold level in moderately severe chronic obstructive pulmonary disease].

In order to study the efficiency of individual training programs at the ventilatory threshold level, twenty COPD patients were randomized into two groups and studied over a two-month period. At the start, during, and at the end of the study all subjects performed incremental exercise tests. The trained group (59.60 SEM +/- 2.75 years) walked four times a week at the heart rate corresponding to the metabolic level of ventilatory threshold. The other group served as controls (58.2 +/- 1.80 years). A marked increase in the symptom-limited oxygen consumption (+/- 25%) (p < 0.01), the maximal ventilation (+20%) (p < 0.01), and the ventilatory threshold (+19%) (p < 0.05) was found in the trained group. No modification was recorded in the control group. The ventilatory pattern at submaximal intensities expressed in percentage of the initial oxygen consumption showed significant differences between groups, the trained-group ventilation decreased at 50% and 75% VO2 sl (p < 0.05). The breathing frequency also decreased at 50% and 75% VO2 sl (p > 0.05). Moreover, we observed an increase in the oxygen pulse at 50% VO2 sl (p < 0.05). In conclusion, this study demonstrates that individualized training at the ventilatory threshold level increases exercise tolerance and produces better ventilatory comfort in COPD patients.

Anaerobic Threshold↗

PubMed1993

Pulmonary gas exchange and breathing pattern during and after exercise in highly trained athletes.

Highly trained athletes (HT) have been found to show arterial hypoxaemia during strenuous exercise. A lack of compensatory hyperpnoea and/or a limitation of pulmonary diffusion by pulmonary interstitial oedema have been suggested as causes, but the exact role of each is not clear. It is known, however, that interstitial pulmonary oedema may result in rapid shallow breathing (RSB). The purpose of this study was therefore twofold: firstly, to determine the exact role of a lack of compensatory hyperpnoea versus a widened in ideal alveolar minus arterial oxygen partial pressure difference [PA(i)-aO2] in the decrease in partial pressure of oxygen in arterial blood (PaO2) and, secondly, to detect RSB during recovery in HT. Untrained subjects (UT) and HT performed exhausting incremental exercise. During rest, exercise testing, and recovery, breathing pattern, respiratory gas exchange, and arterial blood gases were measured. The PA(i)-aO2 and the difference in tidal volume (VT) between exercise and recovery for the same level of ventilation, normalized to vital capacity of the subject [delta VT(%VC)], were then calculated. A large positive delta VT(%VC) was considered to be the sign of RSB. HT showed a marked hypoxaemia (F = 11.6, P < 0.0001), higher partial pressure of carbon dioxide in arterial blood (F = 3.51, P < 0.05), and lower ideal partial pressure of oxygen in alveolar gas (P < 0.001). The relationship between PA(i)-aO2 and oxygen consumption was the same for the two groups. The widening PA(i)-aO2 persisted throughout recovery for both HT and UT. The RSB was observed in HT during recovery.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

Anaerobic and aerobic components during arm-crank exercise in sprint and middle-distance swimmers.

The purpose of this investigation was to compare anaerobic and aerobic components measured during arm exercise in sprint and middle-distance swimmers and to investigate whether the peak anaerobic power:peak aerobic power ratio (W(an),peak:Waer,peak) was related to specialization for the event and to performance. The W(an0,peak, force at zero velocity (F0), and velocity at zero-force (v0), Waer,peak, peak oxygen uptake (VO2peak), and ventilatory threshold (Thv) were compared during arm exercise tests in sprint (group I, n = 8) and middle-distance (group II, n = 9) competitive male swimmers. Anaerobic indices were estimated by the force-velocity test, an anaerobic test using incremental braking forces; aerobic indices were measured during an incremental aerobic exercise test (30 W.min-1). The W(an),peak and Waer,peak were greater in group I [828 (SEM 70) W; 236 (SEM 12) W] than in group II [678 (SEM 28) W; 230 (SEM 5) W], but the differences were not significant. There were also no significant differences observed between the mean values of F0, v0, VO2peak, and Thv. The W(an0,peak:Waer,peak, however, was significantly higher in sprint swimmers (t = 3.08, P < 0.01). In seven of the swimmers, who had recently performed both the 100-m and 400-m front crawl, a relationship existed between their swim time and the W(an),peak:Waer,peak (100 m: r = -0.80, P < 0.05 and 400 m: r = +0.75, P < 0.05). In conclusion, during arm-crank exercise, we did not observe significant differences in anaerobic and aerobic components between sprint and middle-distance swimmers.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1993

Ventilatory response of prepubertal boys and adults to carbon dioxide at rest and during exercise.

The aim of this study was to determine whether the greater ventilation in children at rest and during exercise is related to a greater CO2 ventilatory response. The CO2 ventilatory response was measured in nine prepubertal boys [10.3 years (SD 0.1)] and in 10 adults [24.9 years (SD 0.8)] at rest and during moderate exercise (VCO2 = 20 ml.kg-1.min-1) using the CO2-rebreathing method. Three criteria were measured in all subjects to assess the ventilatory response to CO2: the CO2 sensitivity threshold (Th), which was defined as the value of end tidal PCO2 (PETCO2) where the ventilation increased above its steady-state level; the reactivity slope expressed per unit of body mass (SBM), which was the slope of the linear relation between minute ventilation (VE) and PETCO2 above Th; and the slope of the relationship between the quotient of tidal volume (VT) and inspiration time (tI) and PETCO2 (VT.tI-1.PETCO2(-1)) values above Th. The VE, VT, breathing frequency (fR), oxygen uptake (VO2), and CO2 production (VCO2) were also measured before the CO2-rebreathing test. The following results were obtained. First, children had greater ventilation per unit body weight than adults at rest (P < 0.001) and during exercise (P < 0.01). Second, at rest, only VT.tI-1.PETCO2(-1) was greater in children than in adults (P < 0.001). Third, during exercise, children had a higher SBM (P < 0.02) and VT.tI-1.PETCO2(-1) (P < 0.001) while Th was lower (P < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1993

Respiratory gas exchange indices used to detect the blood lactate accumulation threshold during an incremental exercise test in young athletes.

The time course of changes in blood lactate concentration and ventilatory gas exchange was studied during an incremental exercise test on a cycle ergometer to determine if the lactate accumulation threshold (LT2) could be accurately estimated by the use of respiratory indices (VT2) in young athletes. LT2 was defined as the starting point of accelerated lactate accumulation. VT2 was identified by the second exponential increase in VE and the ventilatory equivalent for O2 uptake with a concomitant nonlinear increase in the ventilatory equivalent for CO2 output. Twelve trained subjects, aged 18-22 years, participated in this study. The initial power setting was 30 W for 3 min with successive increases of 30 W every minute except at the end of the test when the increase was reduced. Ventilatory flow (VE), oxygen uptake (VO2), carbon dioxide output (VCO2), and ventilatory equivalents of O2 and CO2 were determined during the last 30 s of every minute. Venous blood samples were drawn at the end of each stage of effort and analysed enzymatically for lactate concentration. After each test, LT2 and VT2 were determined visually by two investigators from the graphic results using a double-blind procedure. The results [mean (SEM)] indicate no significant difference between LT2 and VT2 expressed as VO2 [43.98 (1.70) vs 44.93 (2.39) ml.min-1 x kg-1], lactataemia [4.01 (0.28) vs 4.44 (0.37) mM.l-1], or heart rate [171 (3.36) vs 173 (3.11) min-1]. In addition, strong correlations were noted between the two methods for VO2 (r = 0.90, P < 0.001), lactataemia (r = 0.75, P < 0.01), and heart rate (r = 0.96, P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1993

Cardiac role in exercise limitation in asthmatic subjects with special reference to disease severity.

We wanted to assess limitations in cardiorespiratory fitness of asthmatic subjects, acclimatized to 1,300 m altitude and in a clinically stable state. We therefore studied 16 young asthmatic and 8 normal young subjects during an incremental bicycle exercise test. The asthmatics were divided into two groups, according to the Aas classification: a moderate asthma group (degree 2 and 3, no pulmonary impairment during symptom-free intervals), and a severe asthma group (degree 4 and 5, with persistent airway obstruction). The results showed that cardiorespiratory fitness is limited in severe asthmatic subjects acclimatized to an altitude of 1,300 m, due to decreased cardiac output and stroke volume. At submaximal exercise, the lower stroke volume is compensated by an increased arteriovenous oxygen content difference, but this compensation no longer exists at maximal exercise, which explains the lower maximal oxygen uptake in the severe asthma group. The hypothesis that the high tidal volume in the severe asthma group could lead to a decrease in left ventricular performance is considered. In conclusion, with respect to cardiorespiratory response to exercise, asthmatics should not be considered as a homogeneous group. Furthermore, relationship between ventilatory requirement and its consequences upon cardiac stroke volume provides a strong argument for the physical rehabilitation of asthmatics. Indeed, aerobic training can decrease the ventilation level for a given workload, and thus reduce inappropriate adaptations to exercise.

Adolescent↗

PubMed1992

The effect of shuttle test protocol and the resulting lactacidaemia on maximal velocity and maximal oxygen uptake during the shuttle exercise test.

The purpose of this study was to investigate the influence of the shuttle test protocol (20-MST) and the resulting lactacidaemia on maximal velocity (Vmax) and maximal oxygen uptake (VO2max). Firstly, three randomly assigned tests to exhaustion were performed by 12 subjects: the treadmill test, the 20-MST, and a continuous running track test using the same prerecorded 1-min protocol as in the 20-MST (T1). One week later, subjects performed another track test, which was conducted up to the same level of effort as attained during the 20-MST (T2). For each test, Vmax, VO2max, lactate concentration at rest and during recovery, maximal heart rate, and distance covered were determined. The results indicated that the 20-MST underestimated Vmax; only T1 satisfactorily assessed Vmax (F = 15.49, P < 0.001). At the same level of effort, the peak blood lactate concentration (t = 2.7, P < 0.02) and VO2max (t = 11.35, P < 0.001) values were higher for the shuttle than for the continuous protocol. It was concluded that Vmax was limited by the running backwards and forwards in the protocol of the shuttle test. The higher values of peak blood lactate concentration and its earlier appearance obtained for the shuttle may have been one of the limiting factors of Vmax. However, the higher values of VO2max obtained for the 20-MST were most likely due to a combination of the relative hyperlactacidaemia and the biomechanical complexities required for this type of protocol.

Adolescent↗

PubMed1992

Benefits of caffeine ingestion on sprint performance in trained and untrained swimmers.

The influence of specific training on benefits from caffeine (Caf) ingestion was examined during a sprint test in a group of highly trained swimmers (T) and compared with the response of a group of untrained occasional swimmers (UT). Seven T and seven UT subjects swam freestyle two randomly assigned 2 x 100 m distances, at maximal speed and separated by 20 min of passive recovery, once after Caf (250 mg) and once after placebo (Pla) ingestion. Anaerobic capacity was assessed by the mean velocity (meters per second) during each 100 m and blood was sampled from the fingertip just before and 1, 3, 5, 7, and 9 min after each 100 m for resting and maximal blood lactate concentration ([la-]b,max) determination. The [la-]bmax was significantly enhanced by Caf in both T and UT subjects (P less than 0.01). However, only T subjects exhibited significant improvement in their swimming velocity (P less than 0.01) after Caf or any significant impairment during the second 100 m. In light of these results, it appears that specific training is necessary to benefit from the metabolic adaptations induced by Caf during supramaximal exercise requiring a high anaerobic capacity.

Adolescent↗