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21.
Summary The effects of ageing and life-long endurance training on the collagen metabolism of skeletal muscle were evaluated in a longitudinal study. Wistar rats performed treadmill running 5 days a week for 2 years. The activities of collagen biosynthesis enzymes, prolyl-4-hydroxylase and galactosylhydroxylysyl glucosyltransferase, were highest in the muscles of the youngest animals, decreased up to the age of 2 months and from then on remained virtually unchanged. The enzyme activity in young animals was higher in the slow collagenous soleus muscle than in the rectus femoris muscle. The enzyme activity in the soleus muscle was higher for older trained rats than older untrained rats. The relative proportion of type I collagen increased and that of type III collagen decreased with age, suggesting a more marked contribution by type I collagen to the agerelated accumulation of total muscular collagen. The results show that collagen biosynthesis decreases with maturation and that life-long endurance training maintains a higher level of biosynthesis in slow muscles. 相似文献
22.
H. O. Tikkanen H. K. Näveri M. H. Härkönen 《European journal of applied physiology》1995,70(4):281-287
The effect of progressive, low-intensity endurance training on regulatory enzyme activities in slow-twitch (ST) and fast-twitch (FT) muscle fibres was studied in 32 rats. Of those rats 16 were trained on a treadmill at a running speed of 10m · min–1 5 days a week over an 8-week period. Running time was progressively increased from 15 min to 2 h · day–1. Of the rats 4 trained and 4 sedentary rats were also subjected to acute exhausting exercise. Enzyme activities of phosphofructokinase 1 (PFKI) from glycolysis, -ketoglutarate dehydrogenase (-KGDH) from the Krebs cycle and carnitine palmitoyltransferase (CPT I and II) from fatty acid metabolism in soleus, tibialis anterior and gastrocnemius muscles were measured in trained and sedentary rats. Enzyme activities of individual ST and FT fibres were measured from the freeze-dried gastrocnemius muscle of 8 trained and 8 sedentary rats. In the sedentary rats the activity of PFK1 in tibialis anterior and soleus muscles was 141% and 41% of the activity in gastrocnemius muscle, respectively. The activity of -KGDH in tibialis anterior and soleus muscles was 164% and 278% of the activity in gastrocnemius muscle, respectively. The activity of CPT I in tibialis anterior and gastrocnemius muscles were at the same level, but in soleus muscle the activity was 127% of that in mixed muscle. Endurance training increased enzyme activities of -KGDH and CPT I significantly (P < 0.05) in gastrocnemius muscle but not in soleus or tibialis anterior muscle. After training both -KGDH and CPT II activities were elevated significantly (P < 0.05) in the ST fibres of gastrocnemius muscle, whereas in FT fibres only -KGDH was increased. For PFK1 activity no significant change was observed in ST or FT fibres. After acute exercise, activities of mitochondrial enzymes -KGDH and CPT I tended to be elevated in all muscles. Thus, low-intensity endurance training induced significant peripheral changes in regulatory enzyme activities in oxidative and fatty acid metabolism in individual ST or FT muscle fibres. 相似文献
23.
Summary The purposes of this investigation were to determine the validity of critical power (CP) as a measure of the work rate that can be maintained for a very long time without fatigue and to determine whether this corresponded with the maximal lactate steady-state (lass,max). Eight highly trained endurance cyclists (maximal oxygen uptake 74.1 ml · kg–1 · min–1, SD 5.3) completed four cycle ergometer tests to exhaustion at predetermined work rates (360, 425, 480 and 520 W). From these four co-ordinates of work and time to fatigue the regression of work limit on time limit was calculated for each individual (CP). The cyclists were then asked to exercise at their CP for 30 min. If CP could not be maintained, the resistance was reduced minimally to allow the subject to complete the test and maintain a blood lactate plateau. Capillary blood was sampled at 0, 5, 10, 20 and 30 min into exercise for the analysis of lactate. Six of the eight cyclists were unable to maintain CP for 30 min without fatigue. In these subjects, the mean power attained was 6.4% below that estimated by CP. Mean blood lactates (n = 8) reached a steady-state (8.9 mmol · l–1, SD 1.6) during the last 20 min of exercise indicating that CP slightly overestimated lass, max. Individual blood lactates during the last 20 min of exercise were more closely related to the y-intercept of the CP curve (r=0.78, P<0.05) than either CP (0.34, NS) or mean power output (r=0.42, NS). The present investigation has shown that highly trained endurance cyclists can tolerate previously unreported levels of blood lactate during 30 min of exercise at or near their CP. Blood lactates during continuous exercise are higher than at the same work rate during an incremental test. The CP provides a simple and inexpensive means of assessing the exercise intensity which can be maintained continuously, while avoiding the methodological difficulties associated with ventilatory and lactate thresholds. 相似文献
24.
The effect of ageing in spinal cord injured humans on the blood pressure and heart rate responses during fatiguing isometric exercise 总被引:3,自引:0,他引:3
Groups of 50 healthy male controls and 50 subjects suffering from paraplegia (aged 20–65 years) were examined as to the inter-relationships
between age, paraplegia and the strength, endurance, blood pressure and heart rate responses to fatiguing isometric exercise.
Contractions were maintained in both groups under voluntary effort and through a contraction induced by electrical stimulation
in the paraplegic group. All contractions were maintained to fatigue at a tension of 40% of the maximal muscle strength in
either the handgrip or quadriceps muscles. Muscle strength of the handgrip was higher in the paraplegic subjects than in the
controls, averaging 589 N and 463 N, respectively for the two groups. In contrast, quadriceps leg extension strength averaged
696 N in the controls and 190 N in the paraplegic groups; for both groups, ageing was associated with a reduction in muscle
strength. While leg endurance was less in the paraplegic group than the control group, handgrip endurance was similar in the
two groups, endurance increasing with ageing in both the controls and paraplegics. Both systolic and diastolic blood pressures
increased at rest in paraplegic and control subjects with age. The magnitude of the pressor response to exercise also increased
with age. This was true during both voluntary exercise and exercise induced through electrical stimulation in the paraplegic
groups. The heart rate response (change in heart rate during exercise) to a fatiguing isometric handgrip contraction decreased
by about 50% between the ages of 20 and 60 years in both the controls and paraplegics for isometric handgrip exercise. In
contrast, heart rate changed little with age during contractions of the quadriceps muscle in paraplegics which were induced
by electrical stimulation.
Electronic Publication 相似文献
25.
Effects of endurance training on myosin heavy-chain isoforms and enzyme activity in the rat diaphragm 总被引:2,自引:0,他引:2
Takao Sugiura Akio Morimoto Naotoshi Murakami 《Pflügers Archiv : European journal of physiology》1992,421(1):77-81
We investigated the effects of endurance training (20 m/min, 60 min/day, 5 days/week) on myosin heavy-chain (MHC) isoforms and succinic dehydrogenase (SDH) activity in rat crural and costal diaphragms, and plantaris muscles. Although the 4-week endurance training produced significant (P<0.05) increases, both in SDH activity and the percentage of isoform HCIIa in the plantaris of the trained rat compared with the sedentary control rat, these alterations did not occur in either the crural or costal diaphragms. After 10 weeks of endurance training, trained animals had significantly (P<0.05) higher SDH activity in the costal diaphragm and the plantaris. Moreover, a significant (P<0.05) decrease occurred in the percentage of HCIIb in the costal diaphragm, and a significant (P<0.01) decrease in the percentage of HCIIb concomitant with a significant (P<0.05) increase of HCIIa resulted in the plantaris. However, the crural diaphragm did not show any significant changes after 10 weeks of endurance training. These results indicate that endurance training induces an alteration in the expression of an MHC phenotype, in addition to causing an increase in oxidative enzyme activity. However, the alterations in response to endurance training are apparently not uniform, varying between regions and/or kinds of muscles. 相似文献
26.
Human leukocyte response to an endurance race 总被引:3,自引:0,他引:3
A. Vishnu Moorthy Stephen W. Zimmerman M.D. 《European journal of applied physiology》1978,38(4):271-276
Summary The response of circulating leukocytes (WBC's) with regard to changes in number, proportion of neutrophils versus lymphocytes and changes in lymphocyte function as well as proportions of T and B cells was studied in eleven men who ran a 20-mile race. A marked leukocytosis was noted 10–15 min after the race with the predominant increase being polymorphonuclear leukocytes (P<0.001). A significant rise in mean serum cortisol levels was also noted (P<0.001) which correlated with both the increase in total WBC's (P< 0.001) and granulocytes (P<0.001), but not lymphocytes. The increase in serum cortisol was inversely correlated with miles of prior training (P<0.001). An increase in lymphocytes from 1767±112/mm3 to 2431±202/mm3 was less than that previously described in short-term exercise. As with short-term exercise the most significant increase in lymphocytes was in B lymphocytes bearing surface immunoglobulin (P<0.0025). However, in contrast to short-term exercise lymphocytes maintained good in vitro response to the mitogen phytohemagglutinin.This study demonstrates that endurance racing produces a more marked granulocytosis and less lymphocytosis than short bouts of exercise. It is suggested that the degree of leukocytosis is stress dependent in that it was positively correlated with serum cortisol and inversely correlated with prior training.Supported in part by a joint fellowship from the National and Wisconsin Kidney Foundations 相似文献
27.
The world of triathlon has expanded to include all ages and both sexes. One of the largest growing age groups is the master female athlete. It is important for the physical therapist to understand the special needs of this population in order to adequately care for master female athletes so they can participate at a high level and injury-free. Biology of aging, injury prevention and a suggested training program are presented in this Masterclass article. 相似文献
28.
F. Dall'Acqua G. Cristina-Souza A.C. Santos-Mariano R. Bertuzzi C. Rodacki A.E. Lima-Silva 《Brazilian journal of medical and biological research》2021,54(4)
The main movements of artistic swimming demand various physical capacities such as flexibility, strength, power, and muscular endurance. The use of ergogenic resources to potentialize performance in this sport, however, is underexplored and deserves investigation. In the present study, we tested whether caffeine ingestion would improve the execution of movements that are essential in a typical figure competition or routines in artistic swimming (i.e., amplitude in the Ariana, height in the Boost and Barracuda, and time maintained in the Stationary Scull techniques). Sixteen experienced female athlete artistic swimmers (17.4±3.2 years of age, 5.6±2.8 years of artistic swimming practice) performed several movements of artistic swimming after having ingested a capsule containing caffeine (5 mg/kg body mass) or cellulose (placebo). Compared to the placebo, caffeine improved latero-lateral amplitude during the Ariana (P=0.035), the height of the Boost and Barracuda (P=0.028 and 0.009), and maintained duration in Stationary Sculling (P=0.012). Bayes factor analysis, however, indicated substantial evidence of a positive effect of caffeine only on the Barracuda and Stationary Scull techniques. These findings indicated that caffeine improved performance during specific artistic swimming movements. Coaches and athletes should consider caffeine ingestion in their supplementation plans. 相似文献
29.
30.
V.K. Malhotra Navreet Singh R.S. Bishnoi D.S. Chadha P. Bhardwaj H. Madan R. Dutta A.K. Ghosh S. Sengupta P. Perumal 《Medical Journal Armed Forces India》2015,71(4):324-329