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41.
Maria-Izabel Almeida-Silveira Chantal Pérot Francis Goubel 《European journal of applied physiology》1996,72(3):261-266
The aim of this study was the analysis of neurophysiological, mechanical and histochemical parameters to demonstrate muscle adaptation with training. If the parameters studied were to show correlated changes, it would be possible to propose that the neural and the muscle components of motor units are both affected by the training programme used. The training consisted of repeated stretch-shortening cycles known to use extensively fast fibres. After the training period electromyographical reflex activities of the ankle plantar-flexors were recorded in awake rats and then mechanical and histochemical measurements were made on isolated soleus muscles of the control and trained rats. The reflexes studied were the H-response to electrical stimulation of the sciatic nerve and the T-response to an Achilles tendon tap. The H-response analysis indicated a decrease in reflex excitability of the trained muscles. The trained soleus muscle also presented a higher contractility as demonstrated by significantly smaller twitch contraction times and higher maximal velocities of shortening measured during tetanic contractions. The reflex and contractile muscle changes were accompanied by relative increases in the number of type II fibres. The T-response was not significantly modified by training despite the decrease in motoneuron excitability demonstrated by the decrease in H-response. This would suggest that the peripheral components of the reflex pathway such as tendon stiffness and/or spindle sensitivity might be modified by training. This would imply that both the motor and the sensory parts of a muscle are affected by training. 相似文献
42.
William D. McArdle Michael M. Toner John R. Magel Robert J. Spinal Kent B. Pandolf 《European journal of applied physiology》1992,65(3):265-270
Summary The influence of exercise intensity on thermoregulation was studied in 8 men and 8 women volunteers during three levels of arm-leg exercise (level I: 700 ml oxygen (O2) · min–1; level II: 1250 ml O2 · min–1; level III: 1700 ml O2 · min–1 for 1 h in water at 20 and 28°C (T
w). For the men inT
w 28°C the rectal temperature (T
re) fell 0.79°C (P<0.05) during immersion in both rest and level-I exercise. With level-II exercise a drop inT
re of 0.54° C (P < 0.05) was noted, while at level-III exerciseT
re did not change from the pre-immersion value. AtT
w of 20°C,T
re fell throughout immersion with no significant difference in finalT
re observed between rest and any exercise level. For the women at rest atT
w 28°C,T
re fell 0.80°C (P<0.05) below the pre-immersion value. With the two more intense levels of exercise,T
re did not decrease during immersion. InT
w 20°C, the women maintained higherT
re (P<0.05) during level-II and level-III exercise compared to rest and exercise at level I. TheT
re responses were related to changes in tissue insulation (I
t) between rest and exercise with the largest reductions inI
t noted between rest and level-I exercise acrossT
w and gender. For men and women of similar percentage body fat, decreases inT
re were greater for the women at rest and level-I exercise inT
w 20°C (P< 0.05). With more intense exercise, the women maintained a higherT
re than the men, especially in the colder water. These findings indicate that exercise is not always effective in offsetting the decrease inI
t and facilitated heat loss in cool or cold water compared to rest. The factors of exercise intensity,T
W, body fat, and gender influence the thermoregulatory responses. 相似文献
43.
44.
The rate of lactic acid removal in relation to different baselines of recovery exercise 总被引:3,自引:0,他引:3
Summary During strenuous exercise lactic acid (LA) appears in the blood as a result of anaerobic metabolism. The rate at which this LA was removed from the blood after exercise was seen to increase to a maximum with a certain level of post exercise activity. This maximum rate of removal of LA appears to be at approximately 40% of the individual's maximum oxygen uptake when the exercise is performed on a bicycle ergometer. 相似文献
45.
David H. VanDercar Arthur R. Laperriere Liang Yu Shyu Michael F. Ward Philip M. McCabe Arlette Perry Neil Schneiderman 《Psychophysiology》1988,25(6):703-711
A microcomputer automated system for measuring systolic time intervals is described. Electrocardiogram, phonocardiogram, and carotid pulse tracings were measured in 38 healthy male subjects during baseline conditions and during either exercise on a bicycle ergometer or a video-game task. These measurements were recorded on both a traditional 3-channel ECG recorder and the computerized system. Both methods of recording systolic time intervals were independently scored by two different experimenters. In this way, interrater reliability of hand-scoring, intermethod reliability between hand-scoring versus computer-scoring, and interrater reliability of computer-scoring could be assessed. The interrater reliabilities of hand-scored systolic time intervals were generally above .90, ranging from .73 for left ventricular ejection time to .99 for R-R intervals of the ECG, with a mean of .92. The intermethod reliability of the computer versus hand-scored systolic time intervals also proved to be generally above .90, ranging from .76 for S1-S2 components of the phonocardiogram to .99 for R-R, with a mean of .94. The interrater reliabilities of the computer-scored systolic time intervals were all above .90, ranging from .93 for S1-S2 to .99 for R-R, with a mean of .98. These data indicate that the computerized method of scoring systolic time intervals is at least as reliable as the more traditional scoring of paper tracing. 相似文献
46.
Jean -Paul Richalet Claude Soulard Alain Nitenberg Bernard Teisseire Jean de Bovée Sadino Séroussi 《European journal of applied physiology》1981,47(1):27-39
Summary Conditions of oxygen extraction by the myocardium have been studied in 12 subjects (44±9 years old) with pure mitral stenosis without clinical, metabolic or electrical sign of coronary insufficiency.Oxygen-hemoglobin equilibrium curves (OHEC) have been determined on arterial, mixed venous and coronary sinus blood, at rest and during a moderate (60 W, 10 min) exercise performed on a bicycle ergometer in supine position. Physiological values, at rest and during exercise, of the following functional parameters of the OHEC were determined in the in-vivo conditions of pH and PCO2P50, nHill, DS max = maximal value of OHEC slope (DS=SO2/PO2), PDS max, SDS max. The concentration of plasma electrolytes capable to modify one of these parameters was controlled in each blood sample.In coronary sinus blood, P50 rises from 27.5±1.7 to 28.9±1.6 Torr during exercise (p<0.01). At rest, Hill's n in myocardial venous blood (2.67±0.09) is significantly higher than in arterial blood (2.61±0.08, p<0.01). A decrease in DS max (2.67±0.20 to 2.53±0.12%. Torr–1; p<0.01) and an increase in PDS max (20.9±1.9 to 22.6±2.1 Torr, p<0.01) are observed. At rest, the myocardial venous point (PcsO2, ScsO2) is not significantly distinct from the maximal slope point (PDS max, SDS max). After 1 min of exercise, a small gap appears which becomes significant at the end of the exercise (PDS max-PcsO2=0.2 Torr at rest, 2.7 Torr after exercise; SDS max-ScsO2=4.1% at rest, 7.9% after exercise). DS value at the myocardial venous point is only 2% at rest and 6% after exercise, lower than its maximal value.The gap between venous point and DS max point could constitute an error signal in the regulation loop of the coronary circulation. The existence of a physiological receptor, sensitive to instant variations in myocardial tissue PO2 and able to maintain venous point near DS max point could be considered. 相似文献
47.
High-fat diet-feeding increases body weight and adiposity in Syrian hamsters (Mesocricetus auratus), effects due in part to decreased energy expenditure. The effects of voluntary exercise- or cold exposure-induced increases in energy expenditure were examined in fat- or chow-fed, female Syrian hamsters. In Experiment 1, voluntary exercise (10 weeks) caused a moderate hyperphagia and actually increased body weight in both diet groups through increases in lean body mass. Carcass lipid was not affected by by exercise in chow-fed hamsters and only slightly reduced in fat-fed animals. In Experiment 2, chronic (8 weeks) cold exposure (5 degrees C) increased energy intake to the same extent in both dietary groups relative to the warm-exposed (23 degrees C) controls. High-fat diet-induced obesity was largely prevented by cold exposure. Cold exposure reduced lean body mass in chow-fed hamsters, but this carcass component was spared by fat-feeding. These results indicate that the increased metabolic demands of cold exposure were more effective in preventing this form of diet-induced obesity than those of voluntary exercise (80% and 17% reductions in carcass lipid, respectively). These results are discussed in terms of possible beneficial effects of eating a lipid-rich diet prior to winter. 相似文献
48.
W. Schuetz K. Traeger T. Anhaeupl S. Schanda C. Rager J. Vogt M. Georgieff 《European journal of applied physiology》1995,70(1):81-87
Adrenaline infusion of 0.1 g · kg–1 · min–1 in healthy volunteers results in an increase of hepatic glucose production, an increase of the absolute number of occupied -adrenoceptors and specific changes in metabolism. To compare these effects with the changes induced by an endogenous catecholamine release, we investigated healthy volunteers during cycle ergometry. After fasting at least 14 h seven healthy subjects exercised for 90 min at an intensity of 20% below their individual anaerobic threshold. The rate of glucose production as well as the turnover rates of alanine and leucine were calculated using stable isotope tracers. High and low affinity -adrenergic binding sites on lymphocytes were determined by an equilibrium binding assay with (–)125 Iodocyanopindolol. After 90 min of cycling the rate of appearance of glucose increased significantly from means of 2.0 (SD 0.2) to 2.65 (SD 0.50) mg · kg–1 · min–1 with unchanged blood concentrations of glucose and lactate. The flux of the amino acids alanine and leucine decreased significantly from means of 0.91 (SD 0.21) to 0.62 (SD 0.14) mg · kg–1 · min–1 and from 0.40 (SD 0.05) to 0.32(SD 0.04) mg · kg–1 · min–1, respectively. The mean free fatty acid concentration increased significantly from 0.65 (SD 0.33) to 1.27 (SD 0.45) mmol · l–1 during the endurance trial. The increase of glucose turnover and the decrease of amino acid flux point to a metabolic shift towards enhanced utilization of free fatty acids. Adrenaline and noradrenaline concentrations showed a moderate but significant increase from means of 0.61 (SD 0.20) to 0.99 (SD 0.36) nmol · l–1 and from 2.27 (SD 0.75) to 3.46 (SD 0.38) nmol · 1–1, respectively. The number of high affinity -adrenergic binding sites per cell (-adrenoceptors) nearly doubled from 770 (SD 130) to 1490 (SD 150) during 90 min of cycling. The observed endogenous plasma catecholamine concentrations were not sufficient to change significantly the relative receptor occupancy. This would seem to indicate that the aerobic exercise induced effects depended more on the absolute number of occupied -adrenoceptors than on their relative receptor occupancy. When compared to the results of the adrenaline infusion experiment the increases of the hepatic glucose production and the increase of -adrenoceptors were very similar in both groups despite ten times higher adrenaline plasma concentrations in the infusion group. This would seem to indicate that -adrenoceptors mediated effects do not correlate with catecholamine plasma concentrations. 相似文献
49.
Circulating leucocyte subpopulations in sedentary subjects following graded maximal exercise with hypoxia 总被引:4,自引:0,他引:4
Holger Gabriel Thomas Kullmer Lothar Schwarz Axel Urhausen Benno Weiler Petra Born Wilfried Kindermann 《European journal of applied physiology》1993,67(4):348-353
Summary Ten healthy sedentary subjects [age, 27.5 (SD 3.5) years; height, 180 (SD 5) cm; mass, 69.3 (SD 6.3) kg] performed two periods of maximal incremental graded cycle ergometer exercise in a supine position. Randomly ordered and using an open spirometric system, one exercise was carried out during normoxia [maximal oxygen consumption (
O2max)=38.6 (SD 3.5) ml·min–1·kg–1; maximal blood lactate concentration, 9.86 (SD 1.85) mmol·l–1; test duration, 22.6 (SD 2.7) min], the other during hypoxia [
O2max=33.2 (SD 3.2) ml·min–1· kg–1; maximal blood lactate concentration, 10.38 (SD 2.02) mmol·l–1; test duration, 19.7 (SD 2.8) min]. At rest, immediately (0 p) and 60 min (60 p) after exercise, counts of leucocyte subpopulations (flow cytometry), cortisol and catecholamine concentrations were determined. At 0 p in contrast to normoxia, during hypoxia there was no significant increase of granulocytes. There were no significant differences between normoxia and hypoxia in the increases from rest to 0 p in counts of monocytes, total lymphocytes and lymphocyte subpopulations [clusters of differentiation (CD), CD3+, CD4+CD45RO–, CD4+CD45RO+, CD8+CD45RO–, CD8+CD45RO+, CD3+HLA-DR+, CD3–CD16/CD56+, CD3+CD16/CD56+, CD 19+] as well as adrenaline, noradrenaline and cortisol concentrations. The counts of CD3 –CD16/CD56+-and CD8 +CD45RO+-cells increased most. At 60 p, CD3–CD16/CD56+ and CD3+CD16/CD56+-cell counts were below pre-exercise levels and under hypoxia slightly but significantly lower than under normoxia. We concluded that the exercise-induced mobilization and redistribution of most leucocyte and lymphocyte subpopulations were unimpaired under acute hypoxia at sea level. Reduced increases of granulocyte counts during the study and reduced cell numbers of natural killer cells and cytotoxic, not major histocompatibility complex-restricted T-cells, only indicated marginal effects on the immune system. 相似文献
50.
Increased nasal air flow during exercise was examined as a possible heat loss avenue contributing to selective brain cooling in hyperthermic humans. On 2 separate days, eight subjects [mean (SE) age, 26.4 (1.2) years] exercised on a cycle ergometer in a warm room [28 (0.2)°C; 28 (5)% relative humidity] to induce a moderate level of hyperthermia. In one session the nostrils were physically dilatated [average dilatation 1.55 (0.17) times] and in the other they were not (control). Both sessions started with a 5-min resting period; then subjects pedaled at 60 W for 5 min, 100 W for 15 min, and 150 W for 20 min. During dilatation both tympanic temperature (T
ty) and forehead skin blood flow, estimated by laser doppler velocimetry, were significantly lower than during the control exercise of 150 W. Rates of increase of (T
ty) during the 100-W exercise were the same in both conditions; however, during the 150-W exercise with dilatated nostrils (T
ty) increased at a rate significantly lower than during control [1.1 (0.3)°C·h–1 vs 1.5 (0.4)°C·h–1]. The change in the rate of increase of T
ty between conditions was significantly correlated to the degree of nostril dilatation (r = –0.77, P = 0.02), suggesting that the lower (T
ty) observed was due to nostril dilatation. Facial skin temperature was not significantly different between sessions. The results suggest that the nasal cavity may act as a heat exchanger in selective brain cooling of exercising humans. 相似文献