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Biomedical subjects

H Monod

Publications and source records attributed to H Monod.

At least 19 recordsLinked to original sources
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↗
PubMed1989

Force-velocity relationship and maximal anaerobic power during cranking exercise in young swimmers.

To study the effect of growth upon maximal anaerobic power of the upper and lower limbs, the maximal power developed during a cranking force-velocity test was correlated with the height of a vertical jump in different age groups of young swimmers. The youngest swimmers were significantly less powerful than the oldest. Differences in body size partly accounted for the differences in maximal power during cranking exercise (Wmax = 0.31 + 0.048 age; r = 0.526; P less than 0.01; where Wmax was expressed in W.kg BM-1 and age in months; n = 103). The effect of growth upon vertical jump is similar to the effect upon maximal cranking power: the lowest values were similar to those which concerned Wmax.kg-1. There was a very significant correlation between Wmax in cranking (in W.kg-1) and the height of the vertical jump (VJ in cm) (Wmax = 1.15 + 0.145 VJ; r = 0.728; n = 103, P less than 0.01).

Adolescent↗
PubMed1989

Fatigue induced by static work.

Despite its low energy cost, isometric contraction can result in the onset of local muscle fatigue. The onset of fatigue occurs more rapidly when the relative force exerted is greater than 15-20% of the maximum voluntary contraction (MVC) of the muscle considered, and when the contraction time is increased. The maximum maintenance time (limit-time) and the corresponding relative force are linked by a hyperbolic relation. Ischaemia promotes accumulation of acid metabolites produced during contraction, and hinders their elimination, thus constituting the main causal factor in the onset of local muscle fatigue. The introduction of rest periods of sufficient duration to ensure restoration of normal blood flow through the muscle is an effective way of delaying, or even preventing, the onset of muscle fatigue. Other factors may also be taken into account, such as the position in which the static work is performed, and the nature and number of muscles used simultaneously, etc. Numerous laboratory and field studies have allowed the development of various models that take into account the conditions relating to isometric contractions during static work.

Fatigue↗
PubMed1989

Contractile properties of old rat muscles: effect of increased use.

To examine how different kinds of activity affect the composition and contractile properties of aging skeletal muscle, old male rats were strength and swim trained. The mass of weights lifted during the strength training increased by 85 +/- 9% (P less than 0.05), which was accompanied by an increase by 32 +/- 5% (P less than 0.05) of the estimated force developed. The wet muscle weight of the soleus and the plantaris decreased significantly with age. The phenomenon was counteracted but not neutralized by the strength training. Twitch and tetanic tension also decreased significantly with age in both the soleus and plantaris muscle. This was avoided by the strength training. This training also significantly decreased time to peak tension and half-relaxation time of both muscles. The swim training increased the heart-to-body weight ratio by 21 +/- 5% (P less than 0.05) and the endurance of the soleus muscle. Time to peak tension and triosephosphate dehydrogenase activity of the plantaris muscle were strongly correlated (P less than 0.001) with myosin adenosinetriphosphatase activity. The results show that the composition and contractile properties of old skeletal muscle are considerably affected by strength training repeated during a substantial period of old age, whereas swim training only affects the endurance of the skeletal muscle.

Aging↗
PubMed1989

Relationship between the 4 mmol running velocity, the time-distance relationship and the Léger-Boucher's test.

The relationship between distance and best time is roughly linear for distances between 1500 and 5000 m. The slope of this relationship has the dimension of a velocity (Vlim) which can be sustained during a long time. The individual time-distance relationships and the resulting Vlim have been studied in 32 subjects practicing different athletic activities by measuring exhaustion time for 2 to 4 constant-velocity running exercises performed to exhaustion. The velocity corresponding to 4 mmol.l-1 of blood lactate (V4 mmol) has been compared with Vlim. As maximal oxygen uptake is a major factor determining V4 mmol, Vlim and V4 mmol have also been correlated with the result of a field test which is assumed to measure maximal aerobic power (Léger-Boucher's test). This test consists in running until exhaustion at a velocity which increases every two minutes. The higher the velocity at exhaustion (Vléger) is, the higher the maximal oxygen uptake is assumed. Both Vlim and Vléger were very well correlated with V4 mmol (r greater than 0.90) and the average value of Vlim was almost equal to the average value of V4 mmol (13.89 vs 13.71 km.h-1). However, it was not possible to estimate V4 mmol accurately from the values of Vlim or Vléger because the standard errors of estimates were too large.

Exercise↗
PubMed1989

[Changes in blood pressure during static work. Practical implication].

while the cardiocirculatory response to dynamic exercises (e.g. running, cycling, swimming) is the object of the physician's full attention, the cardiovascular repercussions of static exercises, such as weight-lifting, sustained postures in gymnastics or immobilization in judo, are often ignored. Yet any sustained isometric contraction is associated from the art with an increase in blood pressure which may be major and involves about equally the systolic and diastolic pressures. As soon as the strength developed by the muscle exceeds 20 p. 100 of its maximum voluntary strength (MVS) the increase of blood pressure continues until the contraction comes to an end. Whatever the muscle used, the intensity of a cardiovascular response is independent of the muscular mass in action, but it mostly depends on the MVS percentage This rise in blood pressure is mainly due to an increase in heart and cardiac output. The reactions are such that relatively moderate and localized static effort may result in a rapid and important increase in myocardial work, and this may cause serious accidents in subject with a cardiovascular weakness, either isolated or associated with such risk factors as age or arterial hypertension. In consequence, adults who are insufficiently trained and present with one or several risk factors should avoid sports which required frequent respiratory arrests and/or sustained postures. If such sports are nevertheless chosen, it would seem that practising also a dynamic sport relying on aerobic metabolism might lin , at least in part, the effects of increased blood pressure due to static activities.

Adult↗
PubMed1979

Physiological effects of dynamic work on a bicycle ergometer combined with different types of static contraction.

The effects on heart rate, oxygen uptake, and pulmonary ventilation of muscular exercises, including both dynamic contractions, either simple or combined, were studied in 4 male subjects, aged 21 to 23 years. The dynamic work consisted in cycling on an ergometric bicycle at three power levels: 40, 80, and 100 W. The static work consisted in pushing against, pulling and holding with the arms a 6, 9, 12, or 18 kg load. The physiological effects are expressed as cardiac cost (delta HR), oxygen cost (delta VO2) and ventilation cost (delta V). The physiological cost of the combined work increases according to the cycling power and to the isometric load developed. A statistical analysis shows that the costs of combined work are not different from the sum of the costs of the static and dynamic contractions measured separately. Thus, the physiological responses to the combinations investigated are of an additive type.

Adult↗