H. Monod

All out anaerobic capacity tests on cycle ergometers

SummaryWe have studied the effects of the braking force on the results of an anaerobic capacity test derived from the Wingate test (an all out 45 s exercise on a Monark 864 cycle ergometer against a given force at the fastest velocity from the beginning to the end of the test). Seven men and seven women participated in the study and performed a total of 63 all-out tests against different braking forces. The same subjects performed a force-velocity test on the same cycle ergometer. Since the relationship between force and velocity is approximately linear for peak velocities between 100 and 200 rev·min−1 (Pérès et al. 1981 a, b; Nadeau et al. 1983; Vandewalle et al. 1983) we characterized each subject by three parameters: P0 (the intercept of the force-velocity regression line with the force axis), V0 (the intercept of the regression line with the velocity axis) and Wmax (maximal power). The relationship between force and mean power was parabolic for the allout anaerobic capacity test. In the present study the optimal force (the force giving the maximal value of mean power during an all out test) was higher for the men (approximately 1 N·kg BW−1) than the force proposed by others (0.853 N·kg BW−1 for Dotan and Bar-Or 1983). However, because of the parabolic relationship between force and mean power, the mean power which corresponds to the optimal force was approximately the same in both studies. The optimal force of the women was equal to 0.9 N·kg BW−1 (0.844 N·kg BW−1 for Dotan and Bar-Or 1983). The optimal force was approximately equal to 47% of P0 for both men and women. In our study maximal anaerobic power and anaerobic capacity could be evaluated with the same force. There was no difference between the men and the women in the anaerobic capacity test when force, mean velocity and mean power were expressed as percentage of P0, V0 and Wmax.

Force-velocity relationship and maximal power on a cycle ergometer

SummaryThe 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 approximatly 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.

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

SummaryThe relationship between the amount of work (Wlim) performed at the end of constantpower 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. TheWlim -tlim realtionship was described by a linear relationship (Wlim =a+b·tlim). Intercepta was roughly equivalent to the work produced during a 1-min exercise performed at MAP. Slopeb was equal to 79% of MAP. Intercepta has been correlated with the total amount of work (AW) performed during a 30-s all-out test supposed to assess anaerobic capacity. Intercepta was significantly (p<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 intercepta. It was likely that the value of intercepta was an underestimation of the maximal anaerobic capacity because of the inertia of the aerobic metabolism. Indeed, an exponential model of theWlim-tlim relationship, which takes the inertia of the aerobic metabolism into account, shows that a linear approximation of theWlim-tlim relationship yields a systematic underestimation of the anaerobic capacity. Consequently, intercepta of theWlim-tlim relationship is not a more accurate estimation of the anaerobic capacity than the AW performed during a 30-s allout test. The inertia of the aerobic metabolism could also explain: (i) that slopeb of theWlim-tlim relationship was lower than MAP, and (ii) that a significant correlation between the anaerobic threshold and slopeb of theWlim-tlim relationship has been found previously.

Sex differences in the sympatho-adrenal response to isometric exercise.

SummaryThe effects on heart rate, blood pressure, and plasma catecholamines (epinephrine, norepinephrine, dopamine) of sustained isometric contraction (SIC) were studied in six women and nine men. Each subject held a tension equivalent to 30% of maximal handgrip strength until exhaustion. There were no significant differences between women and men in the duration of handgrip. Rise of heart rate and blood pressure were similar for women and men. Considering the absolute plasma levels of each catecholamine, no sex differences was observed at rest and at any time during SIC, except for epinephrine whose concentration was higher in men at first min of SIC. On the other hand, women and men exhibited different adrenergic patterns in response to SIC: in the first min of exercise the plasma level of the three catecholamines increased in men whereas for women plasma catecholamines levels were essentially unaffected. Thus, epinephrine seems to play a minor role in the regulation of heart rate and blood pressure during SIC for women. Another interesting result of our study is that SIC is able to induce an increase in dopamine plasma level for women as well as for men.

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<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<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.

Contractility of muscle during prolonged static and repetitive dynamic activity.

The contractility of a muscle is considered as the ability to give series of contractions with or without fatigue. In the first part, the work capacity is successively examined for the static and for the dynamic contractions, using the concepts of limit-time, limit-work and critical force or power. In the second part, an attempt is made to compare the two kinds of muscular contraction, using energetic and biomechanic criteria

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.

Enzymatic adaptations to treadmill training in skeletal muscle of young and old rats

SummaryThe activities of lactic dehydrogenase (LDH), hexokinase (HK), citrate synthetase (CS), and 3-hydroacyl CoA dehydrogenase (HAD), were measured in Soleus and extensor digitorum longus (EDL) muscles of four different age groups of male Wistar rats. Young rats (3 months) and old rats (24 months) were trained during 12 weeks by a 3 days a week running exercises session. Each training session was of 2 h. All the enzymatic activities increased between 3 and 6 months in both Soleus and EDL muscles. During aging (6–27 months) Soleus showed about the same percent decrease in enzymatic activities (30%) for the four enzymes studied. In contrast with Soleus, CS activity of EDL increased with age but HK, LDH, and HAD decreased. The training induced an improvement of all enzymatic activities, except for LDH, which decreased with training in same cases. In the old group the training effect was more important than in the young group. When the relative enzymatic activities were compared it was found that Soleus muscle keeps its energy supply enzyme pattern during aging, whereas EDL evolutes to a more oxidative metabolism. Moreover old skeletal muscle remains trainable and training induces an enzymatic adaptation which follows the same pattern in both muscles: an increase of HK, CS, and HAD activities and a decrease of LDH.

Effects of dynamic, static and combined work on heart rate and oxygen consumption

The effects upon heart rate and oxygen consumption of muscular exercises including simultaneous dynamic and static contractions were studied in three male subjects. Dynamic work consisted of walking at four speeds (0·56, 0·83, 1·11, 1·39 m s−) on a horizontal treadmill; static work consisted of pushing against, pulling and holding 6, 9, 12, 18 and 24 kg; combined work associated walking with each one of the forms of static work. Physiological load is expressed in terms of cardiac cost (ΔHR) and oxygen cost (Δ[Vdot]o2). The physiological cost of combined work increases with both the walking speed and the static load. For each parameter (HR and [Vdot]o2) the extra-cost of combined work has been determined by computing the difference between the cost of combined work and the sum of the costs observed during static and dynamic exercises separately performed. The paired t-test shows significant differences for all of the walking-pushing tests, but only for 8 pulling tests and 2 holding tests. Linear relationsh...

Physiological responses to load holding and load carriage

Abstract Seven young healthy male subjects held and carried loads of 15,20,25, 30 and 40 kg to exhaustion in a lotal of 280 tests. The mean maximum time for load holding was found to be hypcrbolically related to the mass of the load. The for load carrying was shorter than for load holding, and the hyperbolic relationships for both load holding and load carrying were of a form similar to those found for segmental isometric contractions. Heart rate increases (ΔHR) at exhaustion were linearly related to the load, and ΔHR was, for every load, greater when the load was carried rather than simply held. Electromyographic activity in the forearm flexor muscles increased when the load was carried and appeared in the form of marked fluctuations synchronous with the stepping frequency