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Biomedical subjects

H Monod

Publications and source records attributed to H Monod.

At least 55 records · Page 3Linked to original sources
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

Comparison between a 30-s all-out test and a time-work test on a cycle ergometer.

The relationship between the amount of work (Wlim) performed at the end of constant-power exhausting exercise and exhaustion time (tlim) has been studied for supramaximal exercise [105%, 120%, 135% and 150% of the individual maximal aerobic power, (MAP)] performed on a Monark cycle ergometer in nine men. The Wlim--tlim relationship was described by a linear relationship (Wlim = a + b . tlim). Intercept a was roughly equivalent to the work produced during a 1-min exercise performed at MAP. Slope b was equal to 79% of MAP. Intercept a has been correlated with the total amount of work (AW) performed during a 30-s all-out test supposed to assess anaerobic capacity. Intercept a was significantly (p less than 0.05) correlated with AW. The anaerobic capacity was not depleted at the end of the all-out test, as the mechanical power at the 30th s of this test was approximately equal to twice MAP. However, AW was significantly higher than intercept a. It was likely that the value of intercept a was an underestimation of the maximal anaerobic capacity because of the inertia of the aerobic metabolism. Indeed, an exponential model of the Wlim--tlim relationship, which takes the interia of the aerobic metabolism into account, shows that a linear approximation of the Wlim--tlim relationship yields a systematic underestimation of the anaerobic capacity. Consequently, intercept a of the Wlim--tlim relationship is not a more accurate estimation of the anaerobic capacity than the AW performed during a 30-s all-out test.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Anaerobic threshold, muscle volume and hypoxia.

Ventilatory threshold, apparent mechanical efficiency, oxygen debt repayment, heart rate and perceptions of exertion at the ventilatory threshold have been examined in 8 men and 8 women during the performance of four types of exercise (2-leg, 1-leg, arm plus shoulder, and arm ergometry) under normoxic and hypoxic (12% oxygen) conditions. The ventilatory threshold (percentage of task-specific VO2peak at which a disproportionate increase of ventilation begins) was not significantly affected by the sex of the subject, by hypoxia, or by the volume of active muscle involved in the activity, but showed poor reproducibility in small muscle tasks. The apparent mechanical efficiency in 2-leg ergometry was increased from 25.7 to 28.1% under hypoxic conditions, presumably reflecting an increased contribution of anaerobic effort to sub-maximal work. However, oxygen debt repayment following exhausting exercise was much smaller for arm than for leg ergometry. The heart rate corresponding to the ventilatory threshold decreased as the volume of active muscle was reduced. General and respiratory perceptions of effort were rather light for self regulation of an exercise prescription to the ventilatory threshold, and particularly with tasks involving the arm muscles, prescription may best be regulated by the intensity of local muscular sensations.

Adult↗
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

Morphological and biochemical changes in old rat muscles: effect of increased use.

Male Wistar rats were strength and swim trained during a substantial period of old age to determine the influence of aging and activity on the histochemical and metabolic characteristics of a predominantly slow (soleus) and a predominantly fast (plantaris) skeletal muscle. Strength training counteracted the age-related atrophy of the fibers and the age-induced changes in fiber-type distribution of both muscles. Swim training, on the other hand, was without any effect on these parameters. The activity of both mitochondrial and cytoplasmic enzymes became lower with aging in the soleus muscle, whereas only the activity of the cytoplasmic enzymes became lower in the plantaris. Strength training reduced the aerobic capacity of both muscles, whereas swim training had the opposite effect. Aging induced a lower glycogen concentration of the lateral gastrocnemius muscle. This was avoided by swim training. The phosphocreatine and adenosine 5'-triphosphate concentrations were unchanged with aging but became higher with strength training. The activity pattern, therefore, seems to have a considerable influence on the age-related modification of the histochemical and metabolic characteristics of skeletal muscles of the rat. The effect, however, is related to the recruitment pattern of the fiber populations and the form of activity.

Adenosine Triphosphate↗
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↗
PubMed1988

Peak oxygen intake and hypoxia: influence of physical fitness.

Eight men and eight women each performed peak oxygen intake tests on a cycle ergometer breathing ambient air and a mixture of 12% oxygen in nitrogen (equivalent to an altitude of 4400 m) in the two experiments. Hypoxia induced an average 28% decrease of peak oxygen intake, with a somewhat smaller decrease of power output. There were also small decreases in peak heart rate, peak blood pressure, peak ventilation, and peak blood lactate concentration. The major part of the impairment in oxygen transport was due to a reduction of arterial oxygen saturation, with small contributions from the decrease in heart rate and the decrease of ventilation. Subjects in good physical condition suffered a larger decrement of oxygen transport than their more sedentary colleagues, probably due to an unfavorable ratio of peak diffusing capacity to peak cardiac output. However, in the short term, this handicap could be countered by hyperventilation, and such a tactic could probably improve athletic performance over moderate distances.

Adult↗
PubMed1988

Muscle mass as a factor limiting physical work.

Maximal exercise has been performed by eight men and eight women, using four types of ergometer (2-leg, 1-leg, arm + shoulder, and arm) while breathing room air and while breathing 12% O2. Results have been related to anthropometric estimates of muscle mass in the active limbs. Although significant sex differences of O2 transfer and power output are shown, the sex-specific aerobic performance was roughly proportional to active muscle volume (both when comparing individuals on a given type of ergometer and when comparing average scores of the several types of ergometer). However, the relationship was closer for steady power output than for peak O2 intake (where the scores for arm work were boosted by the use of accessory muscles and by hyperventilation). When breathing 12% O2, the 2-leg performance was substantially reduced (an average of 28.7% for O2 transport and 19.2% for power output). This effect dropped to 9.1% for O2 transport and 12% for power output in one-leg ergometry and was negligible for arm or arm plus shoulder work. It is argued that because of difficulty in perfusing small muscles, arm work is limited largely by the intrinsic power of the active muscles, that single-leg ergometry is limited rather equally by central circulatory and muscular factors, and that two-leg ergometry is almost entirely dependent on the central circulatory transport of O2.

Adult↗
PubMed1987

Force-velocity relationship and maximal power on a cycle ergometer. Correlation with the height of a vertical jump.

The force-velocity relationship on a Monark ergometer and the vertical jump height have been studied in 152 subjects practicing different athletic activities (sprint and endurance running, cycling on track and/or road, soccer, rugby, tennis and hockey) at an average or an elite level. There was an approximately linear relationship between braking force and peak velocity for velocities between 100 and 200 rev.min-1. The highest indices of force P0, velocity V0 and maximal anaerobic power (Wmax) were observed in the power athletes. There was a significant relationship between vertical jump height and Wmax related to body mass.

Adolescent↗
PubMed1986

Effect of arm position on cardiovascular responses during isometric handgrips.

Sixteen subjects (eight women and eight men, age 20-25 years) carried out in the seated position, isometric contractions sustained until exhaustion of the digital flexors. The subject's arm was placed in two positions, high and low. The muscle tensions used were 30, 40 and 50% of maximum voluntary contraction (MVC). Under these conditions, for a given relative force, the duration of contraction (limit-time) was not modified by the arm position. In the male subjects, increases in heart rate (HR) and systolic blood pressure (SBP) were slightly more pronounced in the low than the high position, but the differences were not significant. Limit times in the high position were similar to those in the low position, and, in the absence of an increase in HR and SBP, this seemed to be due to an increase in cardiac output consequent upon a transient improvement in venous return together with an increase in the coefficient of oxygen utilization.

Adult↗