19 research outputs found
Pygmy locomotion
No full textThe hypothesis that Pygmies may differ from Caucasians in some aspects of the mechanics of locomotion was tested. A total of 13 Pygmies and 7 Caucasians were asked to walk and run on a treadmill at 4-12 km.h-1. Simultaneous metabolic measurements and three-dimensional motion analysis were performed allowing the energy expenditure and the mechanical external and internal work to be calculated. In Pygmies the metabolic energy cost was higher during walking at all speeds (P < 0.05), but tended to be lower during running (NS). The stride frequency and the internal mechanical work were higher for Pygmies at all walking (P < 0.05) and running (NS) speeds although the external mechanical work was similar. The total mechanical work for Pygmies was higher during walking (P < 0.05), but not during running and the efficiency of locomotion was similar in all subjects and speeds. The higher cost of walking in Pygmies is consistent with the allometric prediction for smaller subjects. The major determinants of the higher cost of walking was the difference in stride frequency (+9.45, SD 0.44% for Pygmies), which affected the mechanical internal work. This explains the observed higher total mechanical work of walking in Pygmies, even when the external component was the same. Most of the differences between Pygmies and Caucasians, observed during walking, tended to disappear when the speed was normalized as the Froude number. However, this was not the case for running. Thus, whereas the tested hypothesis must be rejected for walking, the data from running, do indeed suggest that Pygmies may differ in some aspects of the mechanics of locomotion
Loss of muscle oxidative rapacity after an extreme endurance run: The Paris-Dakar foot-race
No full textWe measured changes in maximal oxygen uptake capacity (V̇O2max), ventilation, heart rate, plasma lactate and speed at the end of an incremental exercise test as a consequence of a relay foot race from Paris to Daltar in 6 subjects. Additionally, anthropometric measurements were taken and muscle biopsies from M. vastus lateralis were obtained before and after the race. The latter were analyzed with morphometric methods for fiber size, capillarity and muscle ultrastructural composition. Weight specific V̇O2max was significantly reduced from 62.4 to 60.5 ml/min . kg after the race while absolute V̇O2max and the other endurance related functional variables remained unchanged. Body fat, thigh cross-sectional area and thigh volume showed tendential reduction immediately after the race but regained pre-race values within a few days. Fiber size and capillarity were not affected by the race. Volume density of total mitochondria was significantly reduced from 6.98 to 4.89% of fiber volume. Both subsarcolemmal and interfibrillar mitochondria were significantly reduced by 59 and 21%, respectively. The volume density of satellite cell was increased about three-fold whereas the content of lipofuscin remained constant. It is concluded that extreme endurance events such as a multi-stage relay race may induce a considerable loss of oxidative capacity of skeletal muscle tissue
Loss of muscle oxidative capacity after an extreme endurance race : the Paris-Dakar foot race.
No full textWe measured changes in maximal oxygen uptake capacity (V̇O2max), ventilation, heart rate, plasma lactate and speed at the end of an incremental exercise test as a consequence of a relay foot race from Paris to Daltar in 6 subjects. Additionally, anthropometric measurements were taken and muscle biopsies from M. vastus lateralis were obtained before and after the race. The latter were analyzed with morphometric methods for fiber size, capillarity and muscle ultrastructural composition. Weight specific V̇O2max was significantly reduced from 62.4 to 60.5 ml/min . kg after the race while absolute V̇O2max and the other endurance related functional variables remained unchanged. Body fat, thigh cross-sectional area and thigh volume showed tendential reduction immediately after the race but regained pre-race values within a few days. Fiber size and capillarity were not affected by the race. Volume density of total mitochondria was significantly reduced from 6.98 to 4.89% of fiber volume. Both subsarcolemmal and interfibrillar mitochondria were significantly reduced by 59 and 21%, respectively. The volume density of satellite cell was increased about three-fold whereas the content of lipofuscin remained constant. It is concluded that extreme endurance events such as a multi-stage relay race may induce a considerable loss of oxidative capacity of skeletal muscle tissue
The energy cost of running increases with the distance covered
No full textThe net energy cost of running per unit of body mass and distance (C(r), ml O2.kg-1.km-1) was determined on ten amateur runners before and immediately after running 15, 32 or 42 km on an indoor track at a constant speed. The C(r) was determined on a treadmill at the same speed and each run was performed twice. The average value of C(r), as determined before the runs, amounted to 174.9 ml O2.kg-1.km-1, SD 13.7. After 15 km, C(r) was not significantly different, whereas it had increased significantly after 32 or 42 km, the increase ranging from 0.20 to 0.31 ml O2.kg-1.km-1 per km of distance (D). However, C(r) before the runs decreased, albeit at a progressively smaller rate, with the number of trials (N), indicating an habituation effect (H) to treadmill running. The effects of D alone were determined assuming that C(r) increased linearly with D, whereas H decreased exponentially with increasing N, i.e. C(r) = C(r0) + aD + He(-bN). The C(r0), the "true" energy cost of running in nonfatigued subjects accustomed to treadmill running, was assumed to be equal to the average value of C(r) before the run for N equal to or greater than 7 (171.1 ml O2.kg-1.km-1, SD 12.7; n = 30). A multiple regression of C(r) on N and D in the form of the above equation showed firstly that C(r) increased with the D covered by 0.123%.km-1, SEM 0.006 (i.e. about 0.22 ml O2.kg-1.km-1 per km, P < 0.001); secondly, that in terms of energy consumption (obtained from oxygen consumption and the respiratory quotient), the increase of C(r) with D was smaller, amounting on average to 0.08%.km-1 (0.0029 J.kg-1.m-1, P < 0.001) and thirdly that the effects of H amounted to about 16% of C(r0) for the first trial and became negligible after three to four trials
Hemodynamic effects of resistive breathing
No full text To examine the acute hemodynamic effects induced by large swings in intrathoracic pressure such as may be generated by obstructive lung disease, airway obstruction was simulated by means of two different fixed external alinear resistances and the results were compared with those for unobstructed breathing (C). Eight normal subjects breathed through external resistances during inspiration (I), expiration (E), or both (IE) at rest (Re) and exercise (Ex). The resistances were chosen to induce similar mouth pressure (Pm) swings at Re and Ex. Pleural pressures (Ppl) were found to correlate closely with Pm. During IE resistive breathing mean swings in Pm were -31 and +19 cmH2O at Re and -38 and +22 cmH2O at Ex, with a corresponding decrease in minute ventilation (-30 and -18%) and an increase in end-tidal PCO2 (+5.6 and +4.2 Torr); these were associated with an increase in heart rate (delta HR = 4 and 6 beats/min) and systolic systemic arterial pressure (delta Psas = 10 and 14 Torr at Re and Ex, respectively). O2 consumption and cardiac output did not change. The myocardial O2 consumption, estimated from the product HR X (Psas--Ppl), increased by 17 and 20% at Re and Ex, respectively. Changes in mechanics, gas exchange, and hemodynamics were less pronounced during I or E resistive loading. It is concluded that breathing through a tight external resistance during IE at Re and Ex increases the metabolic load on the myocardium. </jats:p
Energetics of locomotion in African pygmies
No full textThe energy cost of walking (Cw) and running (Cr), and the maximal O2 consumption (VO2max) were determined in a field study on 17 Pygmies (age 24 years, SD 6; height 160 cm, SD 5; body mass 57.2 kg, SD 4.8) living in the region of Bipindi, Cameroon. The Cw varied from 112 ml.kg-1.km-1, SD 25 [velocity (v), 4 km.h-1] to 143 ml.kg-1.km-1, SD 16 (v, 7 km.h-1). Optimal walking v was 5 km.h-1. The Cr was 156 ml.kg-1.km-1, SD 14 (v, 10 km.h-1) and was constant in the 8-11 km.h-1 speed range. The VO2max was 33.7 ml.kg-1.min-1, i.e. lower than in other African populations of the same age. The Cr and Cw were lower than in taller Caucasian endurance runners. These findings, which challenge the theory of physical similarity as applied to animal locomotion, may depend either on the mechanics of locomotion which in Pygmies may be different from that observed in Caucasians, or on a greater mechanical efficiency in Pygmies than in Caucasians. The low Cr values observed enable Pygmies to reach higher running speeds than would be expected on the basis of their VO2max
Potentiel antimicrobien des extraits de feuilles d’Hyptis suaveolens poit
No full textL’activité antimicrobienne des extraits des feuilles d’Hyptis suaveolens a été évaluée sur quelques microorganismes afin de justifier l’usage traditionnel de la plante. Les extractions successives ont été réalisées sur 100 g de poudre de feuilles par un système de solvant à polarité croissante. Le meilleur rendement a été obtenu avec l’extraction aqueuse ; soit 4,43% d’extrait sec. Les tests antimicrobiens ont été réalisés par la méthode de dilution en milieu liquide couplée à l’étalement sur E. coli, S. aureus, Salmonella spp., et C. albicans. Parmi les extraits aqueux, éthanolique et chloroformique testés, l’extrait aqueux s’est révélé plus actifs sur E. coli, S. aureus, et C. albicans ; par contre, son action est nulle sur Salmonella spp.. La CMI de l’extrait chloroformique qui a inhibé totalement la croissance de C. albicans a été déterminée à 1,25 mgml-1. Ces résultats révèlent que les feuilles d’H. suaveolens renferment les composés actifs antimicrobiens qui peuvent être exploiter. Mots clés : Feuilles d’Hyptis suaveolens, extraits secs, activité antimicrobienne.POTENTIAL ANTIMICROBIAL OF THE EXTRACTS OF LEAVES OF HYPTIS SUAVEOLENS POIT.The antimicrobial activity of Hyptis suaveolens leaves extracts was evaluated on some microorganisms to justify the traditional use of the plant. Successive extractions were performed on 100 g leaves powder by a solvent system increasing polarity. The best performance was obtained with aqueous extraction : 4.43% dry extract. The antimicrobial tests were performed by the method of inhibition in liquid medium coupled to sprawl on E. coli, S. aureus, Salmonella spp. and C. albicans. Among the aqueous, ethanol and chloroform extracts tested, the aqueous extract was more active against E. coli, S. aureus, and C. albicans ; by cons, its is no effect against Salmonella spp.. The MIC of chloroform extract was determined to 1.25 mgml-1 on C. albicans. These results indicate that H. suaveolens leaves contain active antimicrobial compounds that can be exploit.Keywords: Hyptis suaveolens leaves, dry extracts, antimicrobial activit
