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PubMed1975

Mitochondrial enzymatic adaptation of skeletal muscle to endurance training.

Some mitochondrial enzymatic activities (succinate dehydrogenase, NADH cytochrome reductase, cytochrome oxidase) were studied in the gastrocnemius and soleus muscle of the rat. The modifications of the enzyme activity, induced by endurance training, were found to be functions of 1) daily work load and 2) total training time. The treatment with an effective dose of vasodilating substances (papaverine, nicergoline, dipyridamole, and bamethan) showed that 1) nicergoline, bamethan, and dipyridamole were differently able to shorten the time of appearance of the increase in the enzymatic activities; 2) however, long-term treatments with these drugs did not prove able to modify the plateau level of the enzymatic activity increase, for a given amount of endurance training; 3) the pharmacodynamic effect on enzymatic activities was in no way related to the vasodilating effect of these drugs, since the effect was not observed with papaverine. The transition from a given level of endurance training to a lower one led to a proportional decrease of the mitochondrial enzymatic activities, thus pointing out the relation between amount of training and enzymatic activity. The drugs studied were unable to modify the decrease of enzymatic activity induced by lower work load.

Adaptation, Physiological↗

PubMed1977

Muscle adaptation to extreme endurance training in man.

To evaluate the effect of extreme endurance training on muscle fibre composition and activities of oxidative enzymes in different fibre types biopsies were taken from vastus lateralis, gastrocnemius and deltoideus of elite orienteers. Comparisons were made between the (trained) leg muscles and the (relatively untrained) arm muscles, and with leg muscles of 16--18 years old boys. The orienteers had the same percentage type I fibres and vastus lateralis and gastrocnemius as in deltoideus, but higher percentage type I fibres in vastus lateralis compared with the controls. The similarity between trained and untrained muscle in the orienteers suggests that training had not caused the high percentage type I fibres which rather might be the result of selection of individuals with the best prerequisites for high oxidative capacity. However, the distribution of type II subgroups in the leg muscles of the orienteers differed from both their own deltoideus and leg muscles of the controls, the relationship IIA/IIB being altered in favour of the more oxidative IIA. The leg muscles of the orienteers also showed an increased occurrence of the normally IIC fibre. These latter findings point at the possibility of a training induced alteration in the subgroup pattern. Unlike in the controls there was no significant difference in succinate dehydrogenase activity, measured in single fibres, between type I and II fibres in gastrocnemius of the orienteers. Thus, type II fibres have the ability metabolically to adapt to high oxidative demands. This might to some extent be mediated by a conversion from IIB to IIA form.

3-Hydroxyacyl CoA Dehydrogenases↗

PubMed2026

Muscle mechanical and architectural adaptations in response to different endurance training modalities in older adults.

INTRODUCTION: This study examined the effects of various cycling endurance training modalities, matched for total workload, on muscle mechanical and architectural characteristics in older adults. METHODS: Fifty healthy participants (25 females, 59-79 yrs) were randomly assigned to five age and sex matched groups: one control and four workload-matched training groups (moderate-intensity continuous, heavy-intensity continuous, high-intensity interval, and heavy-intensity continuous in eccentric cycling). Training consisted of three weekly sessions over 8 weeks, with evaluations conducted at the beginning and end of the intervention with maximal voluntary isometric contractions at five different knee angles (90, 75, 60, 45, 30°) and maximal concentric and eccentric isokinetic contractions at five different knee angular velocities (45, 90, 150, 210, 250°/s). Maximum voluntary isometric torque (Tmax) and optimal knee angle (KAopt) were obtained from the isometric contractions; eccentric torque (Tecc) and maximum concentric knee angular velocity (Vmax) were obtained from the isokinetic contractions. The muscle architecture of vastus lateralis (VL) at rest (muscle thickness, pennation angle, and fascicle length) was investigated as well. RESULTS: No statistical differences were detected between groups or time points in VL architecture, in KAopt and in Vmax. A main effect of time was observed for Tmax (p < 0.001, η2p = 0.458) and Tecc (p = 0.002, η2p = 0.191) in all the investigated training groups. The within-group comparisons indicate significant increases in Tmax in the training groups, but not in the control group. CONCLUSIONS: Commonly applied endurance exercises improve muscle mechanical capacity (Tmax and Tecc) in older adults, with no structural (architectural) muscle remodelling, when matched for workload.

Humans↗

PubMed1977

Effects of an endurance training regimen on assessment of work capacity in prepubertal children.

The cardiovascular effects of a 12-week endurance training regimen were studied among normally active and healthy prepubertal children. Twenty-six 8- to 12-year-old children (20 boys and 6 girls) volunteered and 10 acted as control subjects. The training regimen consisted of distance running for progressively longer periods (from 10 to 35 min) 2 to 3 times per week, with 2 additional sessions per week devoted to running games. Those who were trained ran a cumulative average distance of 95.6 km (58.9 miles). Intensity of work was assessed from running pace and heart rate. The target workout intensity was 75% to 80% of aerobic capacity (Vo2 max). Growth and development accounted for increases in height, weight, body circumferences, and diameters, and fat-free body weight. Heart rate (HR) during submaximal workloads, both running and walking, decreased in the trained group (p less than 0.01) and (p less than 0.05). HRmax did not change, but Vo2 max increased significantly (average 7%) in the trained group but not in the controls. No significant change attributable to training was found for submaximal cardiac output, stroke volume, or arteriovenous oxygen difference. The Vo2 max value before conditioning was a relatively poor predictor of the magnitude of improvement in functional capacity, but those with higher initial Vo2 max logged more cumulative training mileage. It was concluded that prepubertal children respond to an endurance training regimen by improving their running capacity, which is, to a limited extent, associated with increased aerobic capacity.

Child↗

PubMed1979

Anaerobic threshold alterations caused by endurance training in middle-aged men.

Nine previously sedentary middle-aged males underwent cycle endurance training 45 min/day for 9 wk with an average attendance of 4.1 days/wk. Seven males served as controls. Before and after the training period, the subjects performed three cycle ergometer tests. Work rate was incremented by 15 W/min, to the limit of the subjects' tolerance, in the first two tests; the third test consisted of contant-load cycling at an O2 uptake (VO2) just below the pretraining anaerobic threshold (AT). After training, the AT increased significantly by 44%, expressed as absolute VO2, and by 15%, expressed relative to VO2 max. Significant increases were also noted in VO2max (25%), maximal minute ventilation (19%), and maximal work rate (28%). The test-retest correlation coefficients for the AT (%VO2max) were 0.91, pre- and posttraining. Training did not alter steady-state VO2 during the submaximal exercise test whereas significant decreases occurred in CO2 output, VE, respiratory quotient, and VE/VO2. No changes occurred in the control subjects during this period. These results demonstrate that the AT is profoundly influenced by endurance training in previously sedentary middle-aged males.

Adult↗

PubMed1979

Effects of endurance training on muscle fibre ATP-ase activity, capillary supply and mitochondrial content in man.

Seven young females were subjected to 24 weeks of intensive endurance training. Adaptive changes in myofibrillary ATP-ase activity, capillary supply and mitochondrial content were investigated with light- and electron microscopy in needle biopsies from the quadriceps femoris. 1. The average value for the maximal oxygen uptake increased from 45.7 to 57.2 (ml . kg-1 min-1) (25.2%, P less than 0.005). 2. The average number of capillaries per muscle fibre increased from 1.39 to 1.79 (28.8%, P less than 0.005). Since no significant change in fibre area was found, this suggests that a considerable number of new capillaries have been formed during the training period. 3. An increased capillary supply of all fibre types was found, being greatest for type I and smallest for type IIB. 4. The relative amount of type I fibres before and after the training period was 57.9 and 56.5% respectively (n.s.), for type IIA fibres 26.4 and 31.5% (P less than 0.005), for type IIB fibres 9.2 and 3.4% (P less than 0.005) and for type IIC fibres 0.4 and 2.2% (P less than 0.005). Thus, in the type II group, significant changes in subtypes take place during the endurance training. The data suggest that type IIAB may represent a transitional state between type IIA and IIB. 5. Correlation of capillary supply, myofibrillar ATP-ase activity and mitochondrial content (determined semiquantitatively of individual muscle fibres indicators that the capillary supply to a given fibre is more closely related to its mitochondrial content than to the fibre type as determined on the basis of myofibrillar ATP-ase activity.

Adenosine Triphosphatases↗

PubMed1978

Adaptation of the rat myocardium to endurance training.

The purpose of this study was to assess cardiac adaptation to endurance training in rats. After 11 wk of progressive treadmill exercise (1 h/day), gastrocnemius cytochrome c oxidase activity was 38% higher (P less than 0.01) in the trained (n = 20) as compared to control (n = 20) rats. Cardiac Mg2+-stimulated myofibril ATPase activity (0.308 +/- 0.012 vs. 0.324 +/- 0.006 micrometer.mg-1.min-1) did not change nor was there any change in myofibril protein concentration (60.0 +/- 1.12 vs. 59.9 +/- 0.85 mg.g-1). The isolated left ventricular papillary muscle showed no significant change in time-to-peak tension (TPT) or half-relaxation time. Tension output, however, was significantly increased with training, 2.2 +/- 0.3 vs. 1.5 +/- 0.1 g.mm-2 (P less than 0.025). Furthermore, when the papillary preparations were perfused with 0.5 mM lanthanum (La3+) to displace membrane-bound Ca2+, the time course for tension decay was significantly prolonged in the trained muscles (P less than 0.001). We conclude that endurance running of this type does not necessarily increase myofibril ATPase activity or the time course of the isometric twitch of rat papillary muscle. However, tension output per unit area does increase and this appears to be due to a greater amount of Ca2+ being made available to the contractile apparatus.

Adaptation, Physiological↗

PubMed1977

Effect of endurance training on the capacity of red and white skeletal muscle of mouse to oxidize carboxyl-14C-labelled palmitate.

Three groups of mice were trained for 1, 4 and 5 months according to different running programs on a motor driven treadmill and the fatty acid oxidation capacity (FAO) and the activities of some enzymes of energy metabolism (cytochrome c oxidase, malate dehydrogenase, triosephosphate dehydrogenase, and lactate dehydrogenase) were determined from m. quadriceps femoris (MQF). Endurance training increased the FAO [5-month training 4 days/week, 30 min/day 22% (p less than 0.05); 1-month training, 7 days/week, 150 min/day 37% (p less than 0.001); 4-month training, 5 days/week, 60 min/day 24% (p less than 0.05)]. The activities of cytochrome c oxidase and malate dehydrogenase increased approx. 30% (p less than 0.001) whereas triosephosphate dehydrogenase and lactate dehydrogenase activities were not prominently influenced by training. The predominantly red part of MQF of untrained animals oxidized palmitate four times faster than the predominantly white part. The activities of cytochrome c oxidase and malate dehydrogenase were two times higher showing pronounced FAO in the red part. Endurance training increased the FAO and activities of oxidative enzymes in the red and white parts and in the whole muscle relatively equally resulting in similar differences between the muscle types after training. The absolute increase in the FAO of the red muscle was, however, manyfold when compared in chemical units to the white muscle.

Animals↗

PubMed1977

Cross-sectional and longitudinal evaluations of an endurance training program.

A comparison of the cardiorespiratory responses obtained using both a longitudinal and cross-sectional evaluation of an endurance training program was made in two groups of 60 young male military personnel. Both groups were initially tested (T1) and then retested 6 months later (T2). At T1, Group I was a sample of personnel not participating in a training program while Group II had undergone a 5-month endurance program (2-4 mile run/day). At T2, Groups I and II had been participating in the program for 6 and 11 months, respectively. Testing consisted of sub-maximal and maximal determinations of VO2, VE and heart rate (HR) using an interrupted treadmill test. VO2 max was 11% greater in Group II compared to Group I at T1 and increased 10% in Group I at T2. Similar results were also seen for HR submax, HR max and VE max. These results show that similar values indicative of an improved level of cardiorespiratory fitness can be obtained using either a cross-sectional or longitudinal design when relatively homogeneous groups are studied.

Adolescent↗

PubMed1979

The significance of the aerobic-anaerobic transition for the determination of work load intensities during endurance training.

Anaerobic and aerobic-anaerobic threshold (4 mmol/l lactate), as well as maximal capacity, were determined in seven cross country skiers of national level. All of them ran in a treadmill exercise for at least 30 min at constant heart rates as well as at constant running speed, both as previously determined for the aerobic-anaerobic threshold. During the exercise performed with a constant speed, lactate concentration initially rose to values of nearly 4 mmol/l and then remained essentially constant during the rest of the exercise. Heart rate displayed a slight but permanent increase and was on the average above 170 beats/min. A new arrangement of concepts for the anaerobic and aerobic-anaerobic threshold (as derived from energy metabolism) is suggested, that will make possible the determination of optimal work load intensities during endurance training by regulating heart rate.

Adult↗

PubMed1979

Effect of endurance training on myocardial myosin adenosine triphosphatase activity of the dog.

Endurance exercise training has been found to enhance the functional capacity of the myocardium in several animal models. The sub-cellular phenomena accompanying the augmented function are yet to be explained. The present study sought to determine if the myosin ATPase activity of cardiac muscle increased as a result of endurance conditioning. Five beagles trained by running on a motor driven treadmill (T) and five control (NT) animals were studied. Follwoing 10 weeks of training the T group had a significantly (P less than .05) lower heart rate than the NT while performing the same submaximal exercise and the gastrocnemius cytochrome oxidase activity was significantly greater (P less than .005) in the T than in the NT. These two measurements established that the exercised animals were physically trained. Myosin was isolated from the left ventricular myocardium and activated in a medium containing K-EDTA. No significant (P less than .05) difference in maximum myosin ATPase activity was observed between the NT and T groups in cardiac muscle. It was concluded that cardiac muscle myosin ATPase activity was not affected by 10 weeks of endurance conditioning induced by treadmill running in dogs.

Adenosine Triphosphatases↗

PubMed2026

Endurance training attenuates acute exercise-induced monocyte transcriptomic responses in adolescents: sex-specific molecular adaptations.

Circulating monocytes contribute to atherogenesis and vascular dysfunction. Although clinical cardiovascular disease presents in adulthood, its biological origins often begin in youth and differ substantially between females and males. Twelve males and nine females (13-17 yr) completed an acute exercise protocol consisting of 10, 2-min cycling bouts at 70% of maximal work rate interspersed with 1-min rest intervals, performed before and after an 8-wk supervised endurance training intervention with brief supplementary strength work (60 min/session, 3 sessions/wk). Blood was collected before and immediately after each exercise challenge. Peripheral blood monocytes were isolated, and whole transcriptome RNA sequencing (RNA-seq) was performed. Before training, acute exercise induced a markedly greater monocyte transcriptomic response in females compared with males [5,135 vs. 567 differentially expressed transcripts, false discovery rate (FDR) < 0.1]. Pathway analyses identified vascular function-related pathways in males, whereas females showed enrichment of pathways related to adipose tissue cross talk and oxidative metabolism. Following training, the acute transcriptomic response was markedly attenuated in both sexes (165 transcripts in males and 94 in females, FDR < 0.1), representing an ∼98% reduction in females and a ∼70% reduction in males relative to pre-training responses. These findings reveal sex-specific monocyte responses to acute exercise in youth and suggest that endurance exercise alters immune transcriptional responsiveness in pathways relevant to vascular and cardiovascular health.NEW & NOTEWORTHY Acute exercise induced a markedly greater monocyte transcriptomic response in female adolescents than in males. Females showed activation of pathways related to adipose tissue signaling and oxidative metabolism, whereas males exhibited vascular-function pathways. Following exercise training, the monocyte transcriptomic response to acute exercise was substantially attenuated in both sexes. These findings identify sex-specific immune transcriptional responses to exercise during adolescence with potential implications for cardiovascular health.

Humans↗

PubMed1979

Capillary supply and mitochondrial content of different skeletal muscle fiber types in untrained and endurance-trained men. A histochemical and ultrastructural study.

The number of capillaries per fiber, per mm2, around each fiber type and relative to fiber area was determined in six untrained subjects (UT) and six elite cross-country skiers (ET). Average values for maximal oxygen uptake were 49.8 ml . kg-1 . min-1 (UT) and 77.9 ml . kg-1 . min-1 (ET). Type I fibers constituted 39.2% (UT) and 68.6% (ET), type II A fibers 39.6% (UT) and 19.2% (ET), while 12.8% (UT) and 6.6% (ET) of the fibers were type II B. The mean fiber area for the type II A fibers was significantly greater (p less than 0.01) than the areas for type I and II B in the untrained group. The average numbers of capillaries around each fiber type (CA) were 4.76-4.84-2.94 (UT) and 7.79-6.63-4.5 (ET) for type I, II A, and II B, respectively. There was a significant difference (p less than 0.01) in the CA values relative to fiber area for all fiber types in both groups, being highest for type I and lowest for type II B. The CA increased linearly with increasing size of the fibers for all fiber types in both groups. The mitochondrial content was determined semiquantitatively for each fiber type. The differences in capillary supply between the fiber types are accompanied by similar differences in mitochondrial content. The results indicate that endurance training increases the capillary supply of all fiber types in the human quadriceps muscle. The fact that light microscopical studies have given lower capillarization values than those obtained with the electron microscope is discussed.

Adult↗

PubMed1979

Reduced aldosterone and sodium excretion in endurance-trained athletes before and during immersion.

Aldosterone excretion (AE) and plasma renin activity (PRA) were measured in eight untrained (UT) and eight endurance-trained (TR) male subjects before and during 4 h head-out immersion to study the mechanism of reduced renal sodium excretion in athletes. AE was significantly lower before immersion, and decreased less during immersion, in TR than in UT. Fractional sodium excretion, too, was lower and increased less during immersion in TR than in UT. PRA decreased in the water bath in all subjects (p less than 0.001) with no significant difference between the groups. During immersion, plasma sodium concentration oscillated whereas potassium concentration showed a temporary rise in TR (p less than 0.001). The attenuated response of AE in TR may be due partly to this increase of plasma potassium concentration. The generally reduced aldosterone release in TR might be caused by a training induced adaptation of the adrenals to corticotropin. The lowered renal sodium excretion of TR in spite of the decreased AE suggests an intensified aldosterone effect in these subjects, diminishing the salt loss during exercise.

Adult↗

PubMed1975

Influences of exercise and endurance training on the oxygen dissociation curve of blood under in vivo and in vitro conditions.

In experiments with graded exercise of 15 men (6 untrained, 3 semitrained, 6 endurance-trained) the trained subjects showed a massive shift to the right of the in vivo O2 dissociation curve (ODC) of femoral venous blood. At a saturation of 20 to 25% (18 mkp/sec) Po2 was about 9 mm Hg higher for the trained than for the untrained group. The following factors play a role: 1. The 2,3-diphosphoglycerate [2,3-DPG] concentration was increased by 15 to 20% in the trained group which explains about 2 mm Hg of the diffenence in Po2-2. Exercise acidosis in the femoral venous blood depends to a large extent on CO2 in the trained, but on lactic acid in the untrained group. At low saturations the CO2-Bohr effect increases sharply thus having a greater importance in the trained subjects. This factor can explain about 2 mm Hg of the difference. However, influence of chloride and 2,3-DPG on the Bohr effect must be taken into consideration. 3. Since the large ODC-shift to the right of the trained group was not reproducible under in vitro conditions, it is suggested that a rapidly decaying unknown substance accounts for the remaining difference in Po2.

Acid-Base Equilibrium↗

PubMed1979

Exhaustive exercise, endurance training, and acid hydrolase activity in skeletal muscle.

The activity of eight acid hydrolases and two energy metabolism enzymes were assayed from homogenates of predominantly red (proximal heads of m. vastus lateralis, m. vastus medialis, and m. vastus intermedius) and predominantly white (distal head of m. vastus lateralis) skeletal muscle of mice belonging to one of the following groups: 1) sedentary controls, never trained or exhausted; 2) exhausted controls, exhausted once by running on a treadmill 5, 10, or 20 days before killing; 3) trained mice, exercising until killed; 4) exhausted trained mice, exercising until exhausted 5, 10 or 20 days before killing, not exercising during that period; and 5) detrained mice, terminating training 5, 10, or 20 days before killing. In untrained but not in trained animals, exhaustive exercise caused, 5 days afterward, fiber necrosis and a marked increase in the activities of beta-glucuronidase, beta-N-acetylglucosaminidase, arylsulphatase, ribonuclease, deoxyribonuclease, cathepsin D, and cathepsin C, especially in red muscle fibers. Training increased the activities of citrate synthase, beta-glucuronidase, and cathepsin D in both muscle types and those of beta-N-acetylglucosaminidase, arylsulphatase, and cathepsin C in red muscle. Effects of detraining were minor. Exhaustive exercise causes lethal and evidently also sublethal fiber injuries manifesting themselves as an activation of the lysosomal system of muscle fibers 5 days later. Training affects cellular homeostasis by causing an apparent resistance to the damaging effects of exhaustive exercise. Moderately increased hydrolase activities may reflect increased turnover in endurance-trained muscles.

4-Nitrophenylphosphatase↗

PubMed1978

Capillary supply of skeletal muscle fibers in untrained and endurance-trained women.

Muscle fiber diameters and number of capillaries per fiber, per mm2 and around each fiber were determined in needle biopsies from the lateral part of the quadriceps muscles of 11 young women. Six subjects were untrained (UT) and five were endurance-trained athletes (ET). Average values for maximal oxygen uptake were 43.9 (UT) and 62.1 ml/kg X min (ET). Mean fiber diameter was somewhat smaller in the UT than in the ET group (39.1 and 42.7 micrometer), but the difference was not statistically significant. Fibers with the highest content of mitochondria were on the average 9 micrometer thicker than those with the lowest content. The capillary per fiber ratios were 1.11 +/- 0.07 (mean +/- S.E.) and 1.69 +/- 0.13 in the UT and ET groups, respectively. The number of capillaries around each fiber was 3.04 +/- 0.17 (UT) and 4.42 +/- 0.31 (ET). After correction for shrinkage the number of capillaries per mm2 was 301 (UT) and 404 (ET). The capillary per fiber ratio increased with increasing fiber diameter and with the content content of mitochondria.

Adult↗

PubMed1979

Endurance training and cardiovascular function in 9-and 10-year-old boys.

Thirty-two boys, 9 and 10 years old, were randomly divided into experimental and control groups in order to investigate cardiovascular responses to interval cycle training. The experimental group exercised on a cycle ergometer 5 days a week during their physical education periods. There were 4 work bouts of 4 minutes each, separated by 3-minute recovery intervals each day for 8 weeks. Loads were prescribed so that heart rates ranged from 170 to 195 for each bout (80--90% estimated maximum). The control group took part in a traditional sports-oriented physical education period during this time. Pretest steady-state values at HR130 were determined for oxygen consumption, heart rate, and cardiac output, after which the load was progressively increased to determine physical work capacity at heart rate 170. The tests were repeated after the 8-week training period, at work loads identical to pretest values. Analysis of covariance revealed that significant improvements in the experimental group occurred in stroke volume and oxygen pulse. The 6.5% increase in stroke volume was countered by a 6.8% decrease in heart rate, resulting in no differences in cardiac output. Increases in physical work capacity occurred in each group, but only that of the experimental group was significant. No differences were detected for either group in steady state oxygen consumption or calculated arteriovenous oxygen difference. It was concluded that children of this age level adapt readily to cardiovascular stress. It was suggested that if improvement in cardiovascular fitness is considered to be a valid goal of physical education, then the traditional sports and games should be supplemented by training procedures designed specifically for endurance.

Cardiac Output↗