Ventilatory thresholds determined from HRV: comparison of 2 methods in obese adolescents.

The development of personalised training programmes is crucial in the management of obesity. We evaluated the ability of 2 heart rate variability analyses to determine ventilatory thresholds (VT) in obese adolescents. 20 adolescents (mean age 14.3±1.6 years and body mass index z-score 4.2±0.1) performed an incremental test to exhaustion before and after a 9-month multidisciplinary management programme. The first (VT1) and second (VT2) ventilatory thresholds were identified by the reference method (gas exchanges). We recorded RR intervals to estimate VT1 and VT2 from heart rate variability using time-domain analysis and time-varying spectral-domain analysis. The coefficient correlations between thresholds were higher with spectral-domain analysis compared to time-domain analysis: Heart rate at VT1: r=0.91 vs. =0.66 and VT2: r=0.91 vs. =0.66; power at VT1: r=0.91 vs. =0.74 and VT2: r=0.93 vs. =0.78; spectral-domain vs. time-domain analysis respectively). No systematic bias in heart rate at VT1 and VT2 with standard deviations <6 bpm were found, confirming that spectral-domain analysis could replace the reference method for the detection of ventilatory thresholds. Furthermore, this technique is sensitive to rehabilitation and re-training, which underlines its utility in clinical practice. This inexpensive and non-invasive tool is promising for prescribing physical activity programs in obese adolescents.

[Physical activities and health: results of a national survey of workers]. / Activités physiques et santé: résultats d'une enquête nationale chez les salariés.

Since 15 years, the ASMT (Association for the promotion of sports in enterprises) has been trying to demonstrate that physical activities is a health factor for workers and their enterprises. Few studies (1980-1990) in individual enterprises (Alsthom, IBM, Aérospatiale, Peugeot...), and a national one (1985, 1,600 sportsmen) have shown the relationship between exercise and a lower absenteeism. These results were confirmed by a randomized national controlled study in 1990-1991. With the assistance of 115 work-doctors, the ASMT included more than 22,000 workers: 38% of them had physical activities (ASMT 1: 1 hour a week, ASMT 2: 3 hours a week, ASMT 3: competitors), and 62% had none. Exercisers have less industrial injuries than sedentary people (3.78% vs 4.52%. p. < 0.001) and less absences for illness (26.4% vs 30.8%. p. < 0.001). The duration of their absences are shorter for industrial injuries (sedentary people: 27.9 days, ASMT 1: 27.1 days, ASMT 2: 25.5 days, ASMT 3: 24.6 days) and for illness (sedentary people: 23.6 days, ASMT 1: 19.1 days, ASMT 2: 17.4 days, ASMT 3: 15.3 days).

Physical training decreases total plasma homocysteine and cysteine in middle-aged subjects.

AIMS: The aim of this study was to evaluate whether endurance exercise in middle-aged men induces changes in plasma total homocysteine (tHcy) and total cysteine (tCys), and whether these changes depend on the diet especially on vitamin B(6), folic acid and vitamin B(12) intakes. METHODS: Twelve trained subjects (52.33 +/- 2.4 years) and twelve untrained subjects (56.23 +/- 0.9 years) volunteered for the present study. tHcy and tCys were measured with high-pressure liquid chromatography at rest in both groups and during an incremental exercise performed on a cycle ergometer until exhaustion in the trained subjects. RESULTS: At baseline homocysteinemia and cysteinemia were lower in trained subjects (7.48 +/- 0.4 and 183.45 +/- 13.6 micromol/l) compared with untrained subjects (9.79 +/- 0.4 micromol/l, p < 0.001; 229.01 +/-14.7 micromol/l, p < 0.05, respectively). Incremental exercise also induced a decrease in tHcy and tCys concentrations. Moreover, tHcy concentration was negatively related to the folic acid and B(12) intakes in untrained (r = -0.589, p < 0.05; r = -0.580, p < 0.05, respectively) as well as in trained groups (r = -0.709, p < 0.01; r = -0.731, p < 0.01, respectively) whereas no correlation between tCys and vitamin in the diet was observed. CONCLUSION: This study demonstrates that the combined effects of a chronic physical exercise and a high folate and vitamin B(12) intake could be responsible for the reduction of plasma tHcy and tCys concentrations that might be a key for the prevention of many diseases.

[Disturbance of sports performance after partial sleep deprivation]. / Perturbations de la performance sportive après privation partielle de sommeil.

The changes in cardiac and ventilatory responses were measured in 7 endurance athletes during physical exercise on a bicycle ergometer, taking place after a control night and after a night with partial sleep deprivation in the middle of the night. The results show that, despite the maximal work load was not modified with control, heart rate, ventilation and VE/VO2 ratio (ERO2) were greater at the submaximal (75% of the VO2 max) and maximal work load and oxygen consumption decreased at maximal work, after the night of partial sleep deprivation as compared to the control. These findings suggest that acute sleep loss may contribute to alter the endurance performance by impairment of aerobic pathways.

[Pulmonary fibrosis due to bleomycin]. / Les fibroses pulmonaires à la bléomycine.

Being little myelotoxic, Bleomycin (BLM) is more and more used in association with other anti-neoplastic drugs; its pulmonary toxicity is not to be overlooked and here is a recall of the risks of pulmonary fibrosis during treatment by BLM. This review is based on a personal experience of 45 cases, of which 6 were cases of respiratory insufficiency. It derived also from a study of the literature which expressed the frequency of respiratory accidents in figures varying from 2 to 94% according to the criteria of tolerance used by the authors. BLM toxicity for the pulmonary tract being important some precautions should be taken in its use: specially supervising aged patients or those with a pastpathological respiratory story; it should particularly concern the functional side, using CO ductance to trace the first signs of toxicity A total dose of 450 mg should not be exceeded.

[Value of sophisticated explorative techniques of the pulmonary function in the preoperative evaluation of respiratory risk]. / Intérêt des techniques sophistiquées d'exploration fonctionnelle pulmonaire dans l'évaluation préopératoire du risque respiratoire.

In order to estimate the preoperative evaluation of the respiratory risk, a well adapted clinical examination associated with a routine pulmonary function test (VC, FEV1) can be sufficient. Although some patients with cardiopulmonary disorders or candidates to lung resection need more complex assessments: the flow-volume loop to detect small airways obstruction (MEF 50%, MEF 25%), measure of bronchial hyperreactivity to predict bronchospasm during anaesthesia, residual volume for the diagnosis of emphysema, diffusing capacity (DCO) to discover lung fibrosis: these parameters disruption always make the pronostic worse. It is also useful to couple together preoperative function test and pulmonary scintigraphy to predict post-operative values after lung resection. But, these criteria for operability are not always a good indicator of post-operative complications. So it is possible to use in addition the results of exercise testing to determine cardio-respiratory performances and maximal oxygen consumption (VO2MAX) which seem better correlated with mortality and post-operative lung surgical complications. Preliminary results of our study concerning thirty patients hospitalized in Besancon-St-Jacques Hospital, agree with the hypothesis that exercise testing is an important criterion in the pre-operative evaluation and to predict post-operative mortality and morbidity of patients candidates to thoracic surgery.

Hormonal responses to exercise after partial sleep deprivation and after a hypnotic drug-induced sleep.

The aim of this study was to determine the hormonal responses, which are dependent on the sleep wake cycle, to strenuous physical exercise. Exercise was performed after different nocturnal regimens: (i) a baseline night preceded by a habituation night; (ii) two nights of partial sleep deprivation caused by a delayed bedtime or by an early awakening; and (iii) two nights of sleep after administration of either a hypnotic compound (10 mg zolpidem) or a placebo. Eight well-trained male endurance athletes with a maximal oxygen uptake of 63.5 +/- 3.8 ml x kg(-1) x min(-1) (mean value +/- s(x)) were selected on the basis of their sleeping habits and their physical training. Polygraphic recordings of EEG showed that both nights with partial sleep loss led to a decrease (P< 0.01) in stage 2 and rapid eye movement sleep. A delayed bedtime also led to a decrease (P < 0.05) in stage 1 sleep. Zolpidem had no effect on the different stages of sleep. During the afternoon after an experimental night, exercise was performed on a cycle ergometer. After a 10-min warm-up, the participants performed 30 min steady-state cycling at 75% VO(2-max) followed by a progressively increased workload until exhaustion. The recovery period lasted 30 min. Plasma growth hormone, prolactin, cortisol, catecholamine and lactate concentrations were measured at rest, during exercise and after recovery. The concentration of plasma growth hormone and catecholamine were not affected by partial sleep deprivation, whereas that of plasma prolactin was higher (P < 0.05) during the trial after an early awakening. Plasma cortisol was lower (P < 0.05) during recovery after both sleep deprivation conditions. Blood lactate was higher (P < 0.05) during submaximal exercise performed after both a delayed bedtime and an early awakening. Zolpidem-induced sleep did not affect the hormonal and metabolic responses to subsequent exercise. Our results demonstrate only minor alterations in the hormonal responses to exercise after partial sleep deprivation.

Effects of sleep disturbances on subsequent physical performance.

The purpose of the study was to compare the cardiovascular, respiratory and metabolic responses to exercise of highly endurance trained subjects after 3 different nights i.e. a baseline night, a partial sleep deprivation of 3 h in the middle of the night and a 0.25-mg triazolam-induced sleep. Sleep-waking chronobiology and endurance performance capacity were taken into account in the choice of the subjects. Seven subjects exercised on a cycle ergometer for a 10-min warm-up, then for 20 min at a steady exercise intensity (equal to the intensity corresponding to 75% of the predetermined maximal oxygen consumption) followed by an increased intensity until exhaustion. The night with 3 h sleep loss was accompanied by a greater number of periods of wakefulness (P less than 0.01) and fewer periods of stage 2 sleep (P less than 0.05) compared with the results recorded during the baseline night. Triazolam-induced sleep led to an increase in stage 2 sleep (P less than 0.05), a decrease in wakefulness (P less than 0.05) and in stage 3 sleep (P less than 0.05). After partial sleep deprivation, there were statistically significant increases in heart rate (P less than 0.05) and ventilation (P less than 0.05) at submaximal exercise compared with results obtained after the baseline night. Both variables were also significantly enhanced at maximal exercise, while the peak oxygen consumption (VO2) dropped (P less than 0.05) even though the maximal sustained exercise intensity was not different.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of a selective sleep deprivation on subsequent anaerobic performance.

The aim of the study was to investigate the effects of a partial sleep deprivation on a subsequent supramaximal exercise evaluated from the 30 second Wingate test, and on the following recovery. To take into account the active muscle mass, the Wingate test was performed against a constant braking force related to the data of a force-velocity test conducted on a Monark cycle ergometer (Model 814 E with weights) one week before the experimental test. Eight highly trained athletes were enrolled for this study. The changes in ventilatory and metabolic responses were analyzed during and upon completion of physical 30 second exercise, taking place after two nights, in other words, after a reference night and after a night with reduced sleep. Partial sleep deprivation was obtained by delaying bedtime until 3 a.m. The 30 second Wingate test was performed between 9 a.m. and noon the following days, using a Monark ergometer (Model 814 F). The analyses of change scores disclosed that there were no main significant effects for measures of ventilation, lactates and pH(v) levels under the two experimental conditions. The peak power, the mean power output and the peak velocity recorded after partial sleep deprivation were not modified in comparison with the values obtained after the reference night. These findings suggest that acute sleep loss did not contribute to alterations in supramaximal exercise.

[Tolerance to exertion after sleep reduction and after taking a hypnotic: zolpidem]. / Tolérance à l'effort après réduction de sommeil et après prise d'un hypnotique: le zolpidem.

The aim of the present study was to investigate the effects of a delayed bedtime (3 a.m.), an advanced rising (3 a.m.), a sleep under placebo and under a hypnotic compound, i.e. 10 mg of zolpidem (Stilnox) on sleep structure and on the adaptations to a subsequent exercise in 8 male athletes. The chronology of these nights was randomized and each treatment administered in a double blind fashion. During each experimental night, subjects were monitored with conventional EEG/EOG/EMG polygraphic recordings. The next day, athletic performance was tested using a bicycle ergometer. A codified exercise was performed and consisted to a 10 min warm up followed by a 30 min steady state cycling corresponding to 75% of predetermined VO2 max. Then the work load increased progressively by steps of 10 W every minute until exhaustion. The recovery lasted 30 min. Heart rate, ventilation, VO2, ERO2 were monitored during all exercise and recovery. Plasma lactates and catecholamines were also measured at the same time. The data concerning sleep recordings showed that both nights with partial sleep deprivation resulted in a drop of time spent in slow wave sleep II (decrease of 55%) and in rapid eye movement sleep (decrease of 45%) while the amount of slow wave sleep III and IV were identical to that observed after the reference night. The sleep onset latency and the amount of sleep in stage I was reduced only after the delayed bedtime. Sleep data under zolpidem did not show any significantly difference in the amount of different sleep stages.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamic responses to 30-min cycling exercise at 70% VO2 max both in ambiant air and during chest-immersion.

The aim of this study was to examine the influence of water immersion to the chest on cardio-vascular adaptation to exercise. Upright or sitting immersion causes an increase in central blood volume, but it remains controversial whether central blood volume remains elevated during dynamic exercise in water and facilitates cardiac adaptation, depending particularly on the intensity of exercise which can be matched for O2 consumption (metabolic range) or for mechanical intensity (work load). We have compared hemodynamic variables measured during two cycling exercises at the same mechanical intensity, performed both in ambiant air and during immersion up to the chest.

Influence of exercise duration on serum insulin-like growth factor and its binding proteins in athletes.

The changes in circulating concentrations of insulin-like growth factors during exercise have to date remained incomplete in their documentation. Therefore, we examined in 25 healthy athletes the effects of three different durations of three types of exercise -- incremental ergometer cycling exercise (ICE), long-distance Nordic ski race (NSR) and a treadmill-simulated soccer game (TSG) lasting 20 min, 3 h, and 2 x 45 min separated by a 15-min half-time rest respectively, on plasma concentrations of growth hormone ([GH]), insulin-like growth factor-1 ([IGF-I]) and its binding proteins 1 and 3 ([IGFBP-1], [IGFBP-3]). Compared to baseline, serum [GH] increased by 15.2-fold after ICE (P < 0.001), 2.9-fold after NSR (P < 0.01) and 4.6-fold after TSG. Serum [IGF-I] rose by 11.9% after ICE (P < 0.001), while it decreased by -14.6% after NSR (P < 0.001) and was unchanged after TSG. Serum [IGFBP-1] was slightly increased (1.7-fold) after ICE (P < 0.01), but increased markedly (11.8-fold) after NSR (P < 0.001) and by 6.3-fold after the second session of TSG (P < 0.01) (it remained unchanged at the end of the first period of TSG, i.e. after 45-min exercise). The [IGFBP-3] increased by 14.7% after ICE (P < 0.001) and by 6% after TSG (P < 0.05) while it did not change after NSR. From our results it would appear that [IGFBP-1] increase to bind free IGF and hinder their insulin-like action during long-term exercise (lasting beyond 45 min). It is suggested that IGFBP-1 might thus contribute both to preventing hypoglycaemic action of IGF and to facilitating glucose uptake by muscle cells when muscle glycogen stores become deplete.

Influence of immersion on respiratory requirements during 30-min cycling exercise.

Immersion is considered to facilitate exercise-based rehabilitation. However, the drag effect of moving limbs in water, likely to increase the respiratory requirements at exercise, is not mentioned in many reports. The energetic and ventilatory requirements of 30 min steady state cycling exercise performed by healthy male subjects in air and during immersion up to the xiphoid in 33 degrees C water were compared. In the first experimental series nine subjects exercised at the same 60% maximal oxygen consumption (V'O2,max) in air and water. In the two ambient conditions, ventilatory variables had similar values, but the ergometric setting had to be reduced during water immersion so that the workload rated only 69+/-20 W (mean+/-SD) in water versus 121+/-32 W (p<0.001) in air. In the second experimental series, the same ergometric work load (122 W) was achieved by nine subjects with an average V'O2 of 2,210+/-300 mL x min(-1) in air versus 2,868+/-268 mL x min(-1) in water (p<0.001). Resting water immersion caused a marked trend for decreasing vital capacity (p=0.06), but no modification of other ventilatory variables. During exercise at similar V'O2, the average values of minute ventilation (V'E), tidal volume (VT), respiratory frequency (fR), tidal inspiratory time (VT/tI) were not different between water and air. However, at similar ergometric workload, V'E, VT, fR, VT/tI and plasma lactate levels were significantly higher in water than in air. Such consequences of the drag effect of water upon limb movements have not been reported in previous studies relying on shorter exercise bouts. Thus, maintaining steady exercise levels in water either led to a decrease in the workload or required a 25% higher oxygen consumption than in air. These findings may be relevant to the prescription of water immersion rehabilitation programmes.

Met-enkephalin, beta-endorphin and cortisol responses to sub-maximal exercise after sleep disturbances.

The present study compared the effects of partial sleep deprivation and the effects of an intake of a hypnotic compound (zolpidem) prior to bedtime, on sleep and on hormonal and metabolic adaptations to subsequent exercise. Sleep deprivation consisted of a delayed bedtime and an early getting-up time. Eight young subjects, who slept well and were highly trained athletes, were enrolled in this study. Sleep was recorded polygraphically and the following afternoon exercise was performed on a cycle ergometer for 30 min at 75% of maximal oxygen consumption (VO2max) after a 10-min warm up. Met-enkephalin, beta-endorphin, cortisol, and lactate concentrations were measured at rest and during exercise. The data obtained after experimental sleep, with and without medication were compared with those obtained in the reference condition with normal sleep. Both types of sleep reduction decreased the total sleep time, stage 2 sleep, and rapid eye movement sleep, whereas zolpidem administration did not modify either the duration of sleep or the sleep stages. After the reference night, plasma met-enkephalin did not show any significant change at the end of the submaximal exercise, whereas beta-endorphin, cortisol, and lactic acid concentrations increased significantly in all subjects. The changes in concentration in beta-endorphin were significantly related to the changes in cortisol (r = 0.78; P less than 0.01) and to the changes in plasma lactic acid (r = 0.58; P less than 0.05). Cortisol concentrations were also related to lactic acid values (r = 0.94; P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)