PubMed Health⌕ Search

Biomedical subjects

H Monod

Publications and source records attributed to H Monod.

At least 37 records · Page 2Linked to original sources
PubMed1996

Physiological effects of downhill skiing at moderate altitude in untrained middle-aged men.

To evaluate whether occasional strong physical activity at moderate altitude for several consecutive days is acceptable in untrained middle-aged people, 10 men (age range, 46-59 years) underwent physical examinations before (control day, D0), during (D1-D8), and after 1 wk of leisure alpine skiing. With respect to D0, the resting concentration of plasma noradrenaline (NOR) increased transiently (p < 0.01) on D2 and then increased to a maximal value from D6-D8 (p < 0.01). There was no significant change in the concentration of adrenaline. Although maximal voluntary contraction of knee extensors diminished on D3 (P < 0.05), that of the digit flexors did not change. Heart rate (HR) and blood pressure at rest in the evening were always higher than control values except on D4 (forced rest). After the stay, there was a reduction in sympathetic activity. This was reflected by a return of NOR to its control value, a decrease in resting HR (64.2 [11.4] beats per minute [bpm]: control: 71.1 [10.1] bpm, P < 0.02), a tendency for triglyceride and insulin resistance to decrease, and a significant increase in alipoprotein A1/alipoprotein A2 (P < 0.01). Our results show that despite signs of fatigue on D3, the effects of physical activity that is relatively intense (HR > 70% maximal HR) together with mild hypoxia are well tolerated by untrained middle-aged men and that the controlled practice of downhill skiing may be accepted into a program to lower cardiovascular risk factors.

Acclimatization↗
PubMed1996

Use of physiological criteria for improving physical work conditions.

Physical work is still present in many countries, specially in developing ones. The physiological analysis of the work load could be conducted through two different ways, referring to his energetic cost and/or to the mechanical power of the human motor. The purpose of ergonomics is to organize any physical professional task in order to maintain the workers as much as possible inside the limits of a fatiguing activity. The process of fatigue affects differently a "general activity" and a "local work." If a worker is engaged in a general hard activity, like carrying a load or pushing a trolley, an increase of oxygen consumption or/and an acceleration of the heart rate could be observed. This latter, allowing to estimate the oxygen cost of the work, is more affected if the work is performed in a hot environment. In order to establish the ratio between the data observed at the work place and the maximal working capacity of the organism, it is possible to experiment with the physiological effects of transitory increases of the work stress, by increasing the load or/and the frequency of the repetition of the "unit" of work done. When the task could be described in terms of local work, the correct methodology is based upon the general rules established respectively for the static and the dynamic work. In both the cases, it is possible to determine the critical rate of the muscular activity, the part of the muscular capacity engaged at the work place and the probable time for local exhaustion, in order to limit the duration of each period of work. It should be remembered that 50 years ago, Lucien Brouha proposed that heart rate determinations at work be used as a criteria for a better organization of human work by a non-sophisticated method.

Biomechanical Phenomena↗
PubMed1995

Maximal power and torque-velocity relationship on a cycle ergometer during the acceleration phase of a single all-out exercise.

Seven subjects pedalled on a Monark cycle ergometer as fast as possible for approximately 7 s against four different resistances which corresponded to braking torques (TB) equal to 19, 38, 57 and 76 N.m at the crank level. Exercise periods were separated by 5-min recovery periods. Pedal velocity was recorded every 50 ms by means of a disc with 360 slots fixed on the flywheel, passing in front of a photo-electric cell linked to a microcomputer which processed the data. Every 50 ms, the time necessary to perform half a pedal revolution (t1/2) was computed by adding the 50-ms periods necessary to reach 669 slots (the number of slots corresponding to half a pedal revolution). To measure t1/2 to an accuracy better than 50 ms, this time was computed by a linear interpolation of the time-slot number relationship. Power (P) was averaged during t1/2 by adding the power dissipated against braking torque and the power necessary to accelerate the flywheel. The torque-velocity (T-v) relationship was studied during the acceleration phase of a sprint against a single TB by computing every 50 ms the relationship between v and T (N.m), equal to the sum of TB and the torque necessary to accelerate the flywheel at the same time. The T-v relationships calculated from the acceleration phase of a single all-out exercise were linear and similar to the previously described relationships between peak velocity and braking force.(ABSTRACT TRUNCATED AT 250 WORDS)

Acceleration↗
PubMed1995

Effects of an endurance training programme on the passive and noradrenaline-activated compliances of rat aorta.

The effects of a 12-week endurance training programme (treadmill) upon the passive and the noradrenaline-activated properties of the aorta were studied in 15 trained and 24 sedentary rats. Aortic compliance was studied by measuring the length-tension curves of rings of the descending aorta without (passive properties) and with noradrenaline (noradrenaline activated) in a bubbling Krebs bath kept at a temperature of 37 degrees. The training effect on aortic volume compliance was studied by transforming the tension-length curves into a cross-sectional area-pressure curve according to Laplace's law. The noradrenaline responsiveness was studied by the dose-effect curve. The mechanical data were correlated with the results of a histomorphometric study which measured the aortic wall thickness and the percentages and amounts of elastic, connective and muscle components. Passive aortic compliance and volume compliance were higher in endurance-trained rats whose tunica media presented a lower percentage of collagen and a larger amount of elastic tissue. The dose-effect curve showed that the maximal aortic response to noradrenaline was stronger in trained rats but that the half maximal effective dose was not different. As a consequence, the length-tension curves of the noradrenaline fully activated aorta were similar in trained and sedentary rats except at the highest tensions where collagen is the main factor determining aortic stiffness. The increased noradrenaline response in trained rats was probably the result of the hypertrophy of the smooth muscle cells as maximal active strain (Newtons per square metre) was similar in trained and sedentary rats.

Animals↗
PubMed1994

Detecting a major gene in an F2 population.

The aim of this paper is to study the behavior of the likelihood ratio test for the detection of a major gene in an F2 population. The model is a mixture of three normal distributions where the proportions are known. The information matrix is not positive definite, and therefore classical results cannot be used. An example concerning beans is given.

Animals↗
PubMed1993

Changes in the heart rate and electromyogram beyond the limit time of an isotonic isometric contraction.

Nine men [24.6 (SEM 1.1) years] carried out isometric contractions (IC) of the right elbow flexors at 50% and 100% of the maximal voluntary contraction (MVC). At 50% MVC they had to maintain IC until the limit time (isotonic IC: IIC50) and beyond for as long as possible (anisotonic IC: AIC50). At 100% MVC, IC was anisotonic since the decrease in force was immediate (AIC100). Measurements of the force, the integrated electromyogram (iEMG) and the heart rate (fc) were made during the entire period of contraction. There was a linear relationship between the iEMG increase and the fc increase for IIC50 and AIC100. This relationship was not found for AIC50. The role played by the peripheral information would seem to have become more important in fc regulation when the isotonic IC preceding the anisotonic IC was sufficiently long (submaximal IIC). It would seem that the idea of muscle exhaustion at the limit time was only relative, and depended greatly on the subject's motivation and his capacity to endure a certain degree of pain.

Adult↗
PubMed1993

Cardiovascular responses to leisure alpine skiing in habitually sedentary middle-aged men.

In order to evaluate the cardiovascular responses to leisure alpine skiing of habitually sedentary and not particularly active adult men, a series of continuous recordings of heart rate (HR) was performed on 10 subjects aged 51.0 +/- 1.3 years (mean +/- S.E.) during a 6-day ski trip at an altitude of 1000-2485 m. From the very first day, the subjects spontaneously adopted a regimen of intense physical activity, since 17.9% of the HR values recorded on the ski runs were higher than 85% of the maximal theoretical HR [THRmax (beats min-1) = 220--age (years)], which represented 19.5% of the actual skiing time. On day 2, 10.7% of the HR values were higher than 85% THRmax, or 17.9% of actual skiing time. For the entire ski trip, the mean HR during skiing was approximately 126 beats min-1, which corresponds to 75% THRmax. At rest, HR in the morning did not change significantly from days 2 to 6 (from 80 +/- 4 to 75 +/- 4 beats min-1, P > 0.05), whereas HR in the evening correlated significantly with the duration of physical activity during the day (r = 0.487, P < 0.001). In all cases, HR at rest was significantly higher than before the trip, except in the evening of day 4, the day on which the subjects skied less because they were fatigued after skiing in the morning. Systolic blood pressure (SBP) at rest was always lower than the control established before the trip, whether taken in the morning or in the evening.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1993

Cardiovascular changes during an isometric contraction combined to a cold pressor test.

Fifteen normotensive male subjects (age, 27.9 +/- 1.3 years) performed isometric contractions (handgrip) at 15, 30 and 50% maximal voluntary contraction respectively for 7, 3 and 1 min. The contractions were sustained with or without a cold pressor test of the same duration (immersion of one foot in water of 5.2 +/- 0.1 degrees C). At rest, under the influence of a cold pressor test for 3 min, the heart rate increased from 74.3 +/- 2.2 to 83.3 +/- 2.1 beats min-1 (P < 0.001) in less than 10 s, and returned to the control value in 3 min; on the contrary, at the end of 3 min of cold pressor test, the systolic blood pressure was still above the control value (135.5 +/- 4.2 and 121.0 +/- 3.2 mmHg, P < 0.001). During the contractions, there was no significant difference between heart rate and systolic blood pressure values obtained with or without cold pressor test. Similarly, there was no significant change in the concentrations of plasma catecholamines. This absence of cardiovascular effect of cold pressor test associated with isometric contraction (for three relative force levels) is probably due to the increasing importance of sympathetic cardiac activation produced by the contraction with respect to that produced by the cold pressor test, the absence of supplementary changes in total peripheral resistance and a partial reciprocal inhibition of pain produced by the simultaneous performance of these two tests.

Adult↗
PubMed1992

Effects of endurance training at high altitude on diaphragm muscle properties.

The biochemical, histochemical, and structural changes induced by endurance training and long-term exposure to high altitude were studied in the diaphragm muscle of rats exposed to simulated altitude (HA: n = 16; Pb = 62 kPa, 463 Torr; 4000 m) and compared to animals maintained at sea-level (SL: n = 16). Half of the animals in each group were trained (T) by swimming for 12 weeks, the other half were kept sedentary (S). Except for a small decrease in type I fibres in the HA-S group (-7%, P < 0.05), in favour of type IIab and type IIb fibres, neither high-altitude exposure nor endurance training had an overall affect on fibre type distribution. The mean fibre cross-sectional area was found to be unaffected by altitude and/or chronic exercise. Capillary density was shown to be increased by both high-altitude exposure (P < 0.02) and training (P < 0.001), whereas capillary growth, estimated by the capillary/fibre ratio, was unaffected in both cases. Following endurance training, a modest increase in citrate synthase was shown to occur to the same extent in the HA-T and SL-T groups (+15% and +16% respectively, NS). Hexokinase increased following training (P < 0.05) and high-altitude exposure (P < 0.001). In normoxic and hypoxic animals, endurance training enhanced the ratio of the heart-specific lactate dehydrogenase isozyme LDH1 to total LDH activity (+59%, P < 0.01; +92%, P < 0.05 respectively). It may be hypothesized that the increased glucose phosphorylation capacity observed in diaphragm muscle contributes to the reduction of glycogen utilization during exercise.

Altitude↗
PubMed1992

Respiratory, muscular, and overall perceptions of effort: the influence of hypoxia and muscle mass.

Overall, respiratory and peripheral muscular perceptions of exercise have been examined in 16 subjects (eight men and eight women), each performing four types of exercise (two-leg, one-leg, arm + shoulder, and arm ergometry) under both normoxic and hypoxic (12% oxygen) conditions. Subjects could distinguish ratings for the three types of sensation. Both overall and peripheral muscular perceptions associated with a given oxygen intake or power output increased more than respiratory perceptions as the volume of active muscle was decreased. Hypoxia tended to increase both overall and respiratory perceptions for a given absolute oxygen consumption. Cross-modal comparisons suggested an average overall RPE of close to 13 units at 70% of a task and environment-specific peak oxygen intake, irrespective of exercise conditions, but the SD of individual responses varied by at least +/- 2 units about this average. Peripheral muscular sensations dominated small muscle tasks, but the peripheral muscular RPE became relatively consistent when related to external work rate per liter of active muscle. Respiratory perceptions provided some guide to the intensity of physical activity with a given mode of exercise and fixed environmental conditions. However, if respiratory RPE is used to "fine-tune" cross-modal exercise prescriptions, account must be taken of the distorting influence of active muscle volume and of hypoxia.

Adult↗
PubMed1991

Effects of chronic hypoxia and endurance training on muscle capillarity in rats.

Skeletal muscle capillarity expressed as capillary density (CD), and number of capillaries per fibre (C/F), as well as the mean fibre cross-sectional area (FCSA), were determined in the extensor digitorum longus (EDL), plantaris (PLA) and soleus (SOL) muscles of four groups of eight rodents trained on a swimming exercise programme (T) or maintained sedentary (S), at sea level (SL) or at simulated altitude (HA), barometric pressure 61.7 kPa (463 torr) for 12 weeks. It was shown that both HA exposure and endurance training decreased body and skeletal muscles weights (P less than 0.001). However, neither HA exposure nor endurance training induce any variation in relative importance in the skeletal muscle mass. Altitude exposure and endurance training had increasing effects on CD in all muscles studied (P less than 0.001). This study confirms the fact that altitude exposure has no direct effect on capillary development. On the other hand, the capillary supply of the several slow- and fast-twitch skeletal muscles studied is increased by endurance training. This real enhancement in capillary network is ascertained by an increase in the C/F ratio (+7%, +26%, +16%, in PLA, EDL, and SOL muscles, respectively at sea level, and +19.5%, +30%, and +14% respectively at HA). These results indicate that the effects of chronic exercise on skeletal muscle capillarity estimated by the C/F ratio, are greater in an hypobaric environment than in a SL environment.

Altitude↗
PubMed1991

Cardiovascular response to static handgrip in trained and untrained men.

The influence of aerobic capacity on the cardiovascular response to handgrip exercise, in relation to the muscle mass involved in the effort, was tested in 8 trained men (T) and 17 untrained men (U). The subjects performed handgrip exercises with the right-hand (RH), left-hand (LH) and both hands simultaneously (RLH) at an intensity of 25% of maximal voluntary contraction force. Maximal aerobic capacity was 4.3 l.min-1 in T and 3.21 l.min-1 in U (P less than 0.01). The endurance time for handgrip was longer in T than in U by 29% (P less than 0.05) for RH, 38% (P less than 0.001) for LH and 24% (P less than 0.001) for RLH. Heart rate (fc) was significantly lower in T than in U before handgrip exercise, and showed smaller increases (P less than 0.01) at the point of exhaustion: 89 vs 106 beats.min-1 for RH, 93 vs 100 beats.min-1 for LH and 92 vs 108 beats.min-1 for RLH. Stroke volume (SV) at rest was greater in T than in U and decreased significantly (P less than 0.05) during handgrip exercise in both groups of subjects. At the point of exhaustion SV was still greater in T than in U: 75 vs 57 ml for RH, 76 vs 54 ml for LH and 76 vs 56 ml for RLH. During the last seconds of handgrip exercise, the left ventricular ejection time was longer in T than in U. Increases in cardiac output (Qc) and systolic blood pressure did not differ substantially between T and U, nor between the handgrip exercise tests.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Skeletal muscle changes after endurance training at high altitude.

The effects of endurance training on the skeletal muscle of rats have been studied at sea level and simulated high altitude (4,000 m). Male Wistar rats were randomly assigned to one of four groups: exercise at sea level, exercise at simulated high altitude, sedentary at sea level, and sedentary at high altitude (n = 8 in each group). Training consisted of swimming for 1 h/day in water at 36 degrees C for 14 wk. Training and exposure to a high-altitude environment produced a decrease in body weight (P less than 0.001). There was a significant linear correlation between muscle mass and body weight in the animals of all groups (r = 0.89, P less than 0.001). High-altitude training enhanced the percentage of type IIa fibers in the extensor digitorum longus muscle (EDL, P less than 0.05) and deep portions of the plantaris muscle (dPLA, P less than 0.01). High-altitude training also increased the percentage of type IIab fibers in fast-twitch muscles. These muscles showed marked metabolic adaptations: training increased the activity levels of enzymes involved in the citric acid cycle (citrate synthase, CS) and the beta-oxidation of fatty acids (3 hydroxyacyl CoA dehydrogenase, HAD). This increase occurred mainly at high altitude (36 and 31% for HAD in EDL and PLA muscles; 24 and 31% for CS in EDL and PLA muscles). Training increased the activity of enzymes involved in glucose phosphorylation (hexokinase). High-altitude training decreased lactate dehydrogenase activity. Endurance training performed at high altitude and sea level increased the isozyme 1-to-total lactate dehydrogenase activity ratio to the same extent.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1991

Enzymatic adaptations to treadmill training under the influence of naftidrofuryl acid in diaphragm and limb muscles of old rats.

The effects of training and naftidrofuryl treatment were observed in 21-month-old Long-Evans rats. Rats were injected intraperitoneally twice daily for 8 weeks with 7 mg.kg-1 of naftidrofuryl acid (SN, TN), or with 7 mg.kg-1 fumaric acid (SC and TC) or used as solvent. Training groups (TC, TN) started a progressive 8-week training programme of treadmill exercise. The activities of lactate dehydrogenase (LDH), hexokinase (HK), citrate synthase (CS) and 3-hydroxyacyl-Co-A-dehydrogenase (HAD), were measured in Soleus (SOL), Extensor Digitorum Longus (EDL) and Diaphragm (DIA) muscles. The mean VO2max value was 65 ml.min-1.kg-1 for 21-month-old rats. The training protocol induced increases in the mean VO2max values in the TC and TN groups, 71.8 and 74.4 ml.min-1.kg-1. In sedentary groups (SN), naftidrofuryl increased enzymatic activities (HK, CS, HAD) in the three muscles examined. When the animals underwent 8 weeks of physical training, the enzymatic activities (HK, CS, HAD) increased in SOL, EDL and DIA. When training was combined with naftidrofuryl treatment the increases in enzymatic activities were greater than those induced by training alone. However, the total changes did not differ for the sum of the changes produced by each condition alone.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1991

Lactate steady state velocity and distance-exhaustion time relationship in running.

The relationship between distance and exhaustion time is linear for running exercise at constant velocity lasting 5 to 45 minutes. The slope of this relationship has the dimension of a velocity (VCRIT) which can be sustained during a long time. The individual VCRIT have been studied in 8 runners by measuring exhaustion time for 4 to 5 constant-velocity running exercises performed to exhaustion. The velocity correspond to a lactate steady state (VCHASSAIN) has been estimated according to a two-step protocol proposed by Chassain for exercises on a cycle ergometer. The running velocity corresponding to maximal aerobic metabolism (VLEGER) was estimated by means of the track test proposed by Léger and Boucher. VCRIT was very well correlated (r greater than 0.97) and almost equal to VCHASSAIN. VLEGER was also very well correlated with VCHASSAIN and VCRIT.

Exercise↗
PubMed1990

[The physical fitness visit: a serious medical procedure for the surveillance of sportsmen].

Assessment of physical capability is especially important in sports medicine. It allows the choice of the appropriate sport, and the biomedical follow-up of the health of the sportsman engaged in a monitored training. The so called aptitude examination is a responsible action which requires time, an accurate clinical sense and involves the responsibility both of the general practitioner and of the sport medicine specialist. During the medical follow up, with the help of specialized functional tests, the physician may detect a state of overtraining and start a dissuasive action against doping habits.

Exercise↗