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  • 1
    Electronic Resource
    Electronic Resource
    Effects of protein supplementation during prolonged exercise at moderate altitude on performance and plasma amino acid pattern (1993)
    Springer
    European journal of applied physiology 66 (1993), S. 5-10 
    Details
    ISSN: 1439-6327
    Keywords: Repeated endurance exercise ; Moderate altitude ; Protein ; Free amino acids ; Protein supplementation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of two levels of protein intake on muscle performance and energy metabolism were studied in humans submitted to repeated daily sessions of prolonged exercise at moderate altitude. For this purpose, 29 healthy males, were exposed to seven successive stages of ski-mountaineering at altitudes between 2500 and 3 800 m, and to an isocaloric diet (4000 kcal·day−1, 16760 kJ·day−1) with either 1.5g·kg−1·day−1 (C group,n =14), or 2.5 g·kg−1·day−1 (PR group,n =15) protein intake. Measurements made after the ski-mountaineering programme did not show any change in body mass. The peak torque during maximal isometric voluntary contraction (MVC) of the quadriceps muscle was unaffected by the repeated exercises, whereas the endurance time at 50% MVC was decreased in PR subjects (−26.8%,P〈0.001). Increased levels of both free fatty acids (+147%,P〈0.001) and glycerol (+170%,P〈0.001) observed in C subjects would suggest that lipolysis was enhanced after the repeated exercise. The plasma amino acid pattern was altered after completion of the ski-mountaineering programme; the plasma concentration of the three branched-chain amino acids (BCAA) was significantly decreased in C subjects, whereas the higher level of protein intake (PR group) greatly minimized the exercise-induced decrease in serum BCAA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00863392
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of Growth hormone on rat skeletal muscle after hindlimb suspension (1994)
    Springer
    European journal of applied physiology 69 (1994), S. 337-343 
    Details
    ISSN: 1439-6327
    Keywords: Growth hormone ; Hindlimb suspension ; Muscle atrophy ; Pituitary-intact rats ; Soleus muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To examine the effects of growth hormone (GH) on the preferential atrophy of the soleus muscle (SOL) occurring after hindlimb suspension (HS), two groups of male rats received daily injections of 2 IU · kg −1 body mass of recombinant human growth hormone (rhGH). Rats were either suspended by the tail for 21 days (HS-GH, n = 5) or nonsuspended (CGH, n=5). The effects of rhGH treatment on SOL and extensor digitorum longus muscles (EDL) were compared in two groups of animals receiving daily injections of saline, either suspended by the tail (HS-SA, n = 5) or nonsuspended (C-SA, n = 5). The results showed that the SOL hypertrophy in response to rhGH administration was mostly observed in C rats (+33%, P〈0.01). This increase in muscle mass was correlated with a concomitant increase in the size of type I fibres (+21%, P〈0.05). Although SOL mass decreased during HS in rhGH treated animals (−44%, P〈0.001), the mean normalized mass of this muscle did not significantly differ between C-SA and HS-GH groups. A statistically significant increase in the absolute mass of EDL occurred with rhGH treatment in CGH (+12%, P〈0.05). The HS-induced decrease in the percentage distribution of type I fibres in SOL was unaffected by the rhGH treatment. In addition, a decrease in the citrate synthase activity in the whole SOL was observed in the two groups of tail-suspended rats (−31%, P〈0.05; −21%, P〈0.05 in SA and GH animals, respectively). The activity of 3-hydroxyacyl coenzyme A dehydrogenase was enhanced by the rhGH treatment (P〈0.05) with similar magnitude in both C (+25%) and HS rats (+24%). Therefore, GH prevented only slightly the atrophy of SOL, occurring after 21 days of HS. The effects of rhGH treatment appeared most effective in C rats, suggesting that HS impaired the growth-promoting effects of this hormone on skeletal muscle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392040
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  • 3
    Electronic Resource
    Electronic Resource
    Sodium citrate ingestion and muscle performance in acute hypobaric hypoxia (1995)
    Springer
    European journal of applied physiology 71 (1995), S. 362-368 
    Details
    ISSN: 1439-6327
    Keywords: Alkalising agent ; Muscle fatigue ; Melectric power spectrum ; Simulated high altitude
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Eight subjects were studied on four occasions following ingestion of a 300-ml solution containing either sodium citrate (C, 0.4g · kg−1 body mass) or placebo (P, sodium chloride 0.045 g · kg−1 body mass), at local barometric pressure (N, P B approximately 740 mmHg, 98.7 kPa) or hypobaric hypoxia (HH, P B = 463 mmHg, 61.7 kPa). At 2 h after ingestion of the solution, the subjects performed prolonged isometric knee-extension at 35% of the maximal voluntary contraction (MVC) measured either in N or HH. Results showed that ingestion of C led to an improvement in muscle endurance (P 〈 0.01). However, this increase in endurance time for knee extensor muscles was only significant in N ( +22%, P 〈 0.05, compared to + 15%, NS, at N and HH, respectively). Following ingestion of sodium citrate, pre-exercise bicarbonate concentrations and pH levels were significantly higher than those measured after P ingestion. A significant treatment effect was observed for blood lactate concentrations with values higher for C than for P after 4, 6 and 10 min of recovery (P 〈 0.05). Electromyographic signals (EMG) were obtained from the vastus lateralis muscle during the prolonged isometric contraction at 35% MVC. The mean power frequency (MPF) significantly decreased in time under both N-P and N-C conditions. In HH, no significant decrease in MPF was observed with time. The results suggest that C ingestion was an ergogenic aid enhancing endurance during a sustained isometric contraction. In addition, it is suggested that fatigue during prolonged isometric contraction in HH was not directly related to factors determining the EMG signs of fatigue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00240418
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of chronic low frequency stimulation on structural and metabolic properties of hindlimb suspended rat soleus muscle (1995)
    Springer
    European journal of applied physiology 70 (1995), S. 528-535 
    Details
    ISSN: 1439-6327
    Keywords: Hindlimb suspension ; Chronic low ; frequency stimulation ; Fibre type composition ; Immunohistochemistry ; Biochemical properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The use of chronic low frequency stimulations (CLFS, 10 Hz bipolar current 8 h · day−1) as a countermeasure against unweighting-induced muscle alterations was investigated in rat soleus muscle during 21 days of hindlimb suspension (HS). It was shown that CLFS was able to minimize the soleus muscle atrophy induced by suspension (−29% in stimulated muscles compared to −56% in the non-stimulated soleus muscle). In parallel, CLFS partly prevented the HS-induced decreases in the cross-sectional area of type I fibres and in the total and myofibril protein contents. Stimulation at low frequency reduced the increase in the fast-myosin expression recorded with unweighting. Moreover, the HS-induced increase in glycolytic capacity was counteracted to a considerable extent by CLFS. In conclusion, the results of this study showed that CLFS can only partly prevent the HS-induced modifications in the soleus muscle. However, the limited effectiveness of CLFS to prevent muscle atrophy emphasized the critical role of reduced load bearing in the induction of solens muscle atrophy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00634382
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  • 5
    Electronic Resource
    Electronic Resource
    Muscle damage induced by running training during recovery from hindlimb suspension: the effect of dantrolene sodium (1997)
    Springer
    European journal of applied physiology 76 (1997), S. 421-427 
    Details
    ISSN: 1439-6327
    Keywords: Key words Unloading ; Degeneration ; Muscle regeneration ; Myosin heavy chain ; Calcium antagonist ; Running recovery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We examined the extent of morphological alterations and the myosin heavy chain (MHC) distribution in the rat soleus muscle after a 4-week period of spontaneous recovery or retraining after hindlimb suspension (HS). Moreover, we tested the hypothesis that dantrolene sodium, which affects the flux of calcium over the sarcoplasmic reticulum membrane, was able to attenuate muscle damage. Three groups of rats were submitted to 3 weeks of HS, followed by either 4 weeks of unrestricted cage activity (HC, n = 7), or running training for the same period and were compared to age-matched animals (C, n = 8). Trained rats were treated with either placebo or dantrolene sodium (HTP, HTD, n = 8 each, respectively). Four weeks after HS recovery, the percentage of myofibres with internal nuclei (%in) was determined by histological staining with hematoxylin and eosin. %in was affected by the individual rat (P 〈 0.001), and was higher in the mid-belly region of the muscle (P 〈 0.05). Muscle damage, as estimated by %in, was more extensive in trained rats (i.e. HTP and HTD) than in HC animals (23% and 12%, respectively). Moreover, dantrolene sodium tended to exert a protective effect on training-induced muscle injury. A 12% increase in type I MHC was observed in both HTP and HTD rats, in comparison with group C animals (P 〈 0.001). The relative proportion of type-I MHC was inversely correlated with %in (r = −0.65, P 〈 0.001). Running recovery led to an increased citrate synthase activity in comparison with that of C or HC rats. In conclusion, the present findings demonstrate that running recovery from HS increases the incidence of muscle damage, and that dantrolene sodium administration has only limited protective effects against exercise-induced muscle injury.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050271
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  • 6
    Electronic Resource
    Electronic Resource
    Increase in energy cost of running at the end of a triathlon (1996)
    Springer
    European journal of applied physiology 73 (1996), S. 440-445 
    Details
    ISSN: 1439-6327
    Keywords: Triathlon ; Oxygen uptake ; ventilation ; Biochemical variables ; Plasma volume
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The purpose of the present study was to verify the increase in energy cost of running at the end of a triathlon. A group 11 trained male subjects performed a triathlon (15-km swimming, 40-km cycling, 10-km running). At least 1 week later the subjects ran 10-km as a control at the same pace as the triathlon. Oxygen uptake ( $$\dot V$$ O2), ventilation ( $$\dot V$$ E) and heart rate (HR) were measured during both 10-km runs with a portable telemetry system. Blood samples were taken prior to the start of the triathlon and control run, after swimming, cycling, triathlon run and control run. Compared to the control values the results demonstrated that triathlon running elicited a significantly higher (P 〈 0.005) mean $$\dot V$$ O2 [51.2 (SEM 0.4) vs 47.8 (SEM 0.4) ml·min−1·kg−] $$\dot V$$ E [86 (SEM 4.2) vs 74 (SEM 5.3) l·min−1], and HR [162 (SEM 2) vs 156 (SEM 1.9) beats·min−1)]. The triathlon run induced a greater loss in body mass than the control run [2 (SEM 0.2) vs 0.6 (SEM 0.2) kg], and a greater decrease in plasma volume [14.4% (SEM 1.5) vs 6.7% (SEM 0.9)]. The lactate concentrations observed at the end of both 10-km runs did not differ [2.9 (SEM 0.2) vs 2.5 (SEM 0.2) m·mol·l−1]. Plasma free fatty acids concentrations were higher (P 〈 0.01) after the triathlon than after the control run [1.53 (SEM 0.2) to 0.51 (SEM 0.07) mmol·l−1]. Plasma creatine kinase concentrations rose under both conditions from 58 (SEM 12) to 112 (SEM 14) UI·l−1 after the triathlon, and from 61 (SEM 7) to 80 (SEM 6) UI·l−1 after the control run. This outdoor study of running economy at the end of an Olympic distance triathlon demonstrated a decrease in running efficiency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00334421
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of hindlimb suspension and androgen treatment on testosterone receptors in rat skeletal muscles (1999)
    Springer
    European journal of applied physiology 79 (1999), S. 443-448 
    Details
    ISSN: 1439-6327
    Keywords: Key words Testosterone ; Hindlimb suspension ; Testosterone receptor ; Skeletal muscles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study tested the specific and combined effects of testosterone treatment and hindlimb suspension (HS) on the properties of steroid receptors in skeletal muscle. Male rats were either administered weekly high doses of testosterone heptylate (10 mg · kg−1) or olive oil placebo, and were either tail-suspended or acted as controls. After 3 weeks of treatment, three muscles were excised from each animal, soleus (SOL), extensor digitorum longus (EDL), and plantaris. The results showed that the testosterone treatment was unable to minimise the HS-induced atrophy of skeletal muscle. As expected, HS altered the fibre-type composition of SOL muscles (−33% of type I, +188% and +161% of type IIa and intermediate fibres respectively, P 〈 0.01). No overall effect of treatment was detected on the fibre-type composition of either slow or fast-twitch muscles. Binding capacity determined by a radiocompetition technique was increased by HS, especially in SOL and EDL muscles (P 〈 0.01), while HS or steroid treatment decreased the affinity of the steroid receptors. The combination of HS and testosterone administration resulted in a decrease in binding capacity and affinity of steroid receptors in skeletal muscles. Steroid receptors in fast-twitch muscles exhibited a higher affinity than those in slow-twitch muscles, and it is suggested that it is likely that testosterone treatment is more effective in fast-twitch than in slow-twitch muscles. It was concluded that the lack of preventive effect of testosterone treatment on HS-induced SOL muscle atrophy could be explained by both a decrease in steroid sensitivity and the removal of mechanical factors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050535
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  • 8
    Electronic Resource
    Electronic Resource
    Quantitative assessment of degenerative changes in soleus muscle after hindlimb suspension and recovery (1997)
    Springer
    European journal of applied physiology 75 (1997), S. 380-387 
    Details
    ISSN: 1439-6327
    Keywords: Key words Unloading  ;  Degeneration  ;  Muscle regeneration  ;  Muscle fibre necrosis  ;  Myosin heavy chain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of this study was to quantify the degenerative and regenerative changes in rat soleus muscle resulting from 3-week hindlimb suspension at 45° tilt (HS group, n = 8) and 4-week normal cage recovery (HS-R group, n = 7). Degenerative changes were quantified by microscope examination of muscle cross sections, and the myosin heavy chain (MHC) composition of soleus muscles was studied by sodium dodecyl sulphate polyacrylamide gel electrophoresis. At the end of 3-week hindlimb suspension, histological signs of muscle degenerative changes were detected in soleus muscles. There was a significant variability in the percentage of fibres referred to as degenerating (%dg) in individual animals in the HS group [%dg = 8.41 (SEM 0.5)%, range 4.66%–14.08%]. Moreover, %dg varied significantly along the length of the soleus muscle. The percentage of fibres with internal nuclei was less than %dg in HS-soleus muscles [4.12 (SEM 0.3)%, range 1.24%–8.86%]. In 4-week recovery rats, the greater part of the fibres that were not referred to as normal, retained central nuclei [15.8 (SEM 2.2)%, range 6.2%–21.1%]. A significant increase in the slow isoform of MHC was recorded in the HS-R rats, compared to muscles from age-matched rats (P 〈 0.01). These results would suggest that a cycle of myofibre degeneration-regeneration occurred during HS and passive recovery, and that the increased accumulation of slow MHC observed in soleus muscles after recovery from HS could be related to the prevalence of newly formed fibres.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050176
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  • 9
    Electronic Resource
    Electronic Resource
    Physical performance and metabolic changes induced by combined prolonged exercise and different energy intakes in humans (1994)
    Springer
    European journal of applied physiology 68 (1994), S. 525-530 
    Details
    ISSN: 1439-6327
    Keywords: Diet ; Prolonged exercise ; Physical performance ; Metabolism ; Undereating
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The purpose of this study was to evaluate the effects on physical performance of three levels of energy intake during a 5-day period of prolonged physical exercise and relative sleep deprivation. A group of 27 male soldiers were randomly assigned to three groups receiving either 1800 kcal · 24 h−1 (7560 kJ, LC), 3200 kcal · 24h−1 (13440 kJ, MC) or 4200 kcal-24h−1 (17640 kJ, HC). They took part in a 5-day combat course (CC) of heavy and continuous physical activities, with less than 4 h sleep per day. Performance capacity was tested just before and at the end of CC. Maximal oxygen uptake ( $$\dot V$$ O2max) was determined during an exhausting incremental exercise test on a cycle ergometer. Anaerobic performance was measured from the time during which exercise could be maintained at supra maximal loads on a cycle ergometer. After CC, the subjects receiving LC exhibited a 14% decrease in power output at exhaustion in the incremental exercise test [from 325 (SEM 8) to 278 (SEM 9) W,P 〈 0.001] and a significant decrease in $$\dot V$$ O2max of 8% [from 3.74 (SEM 0.06) to 3.45 (SEM 0.05) l · min−1,P〈0.05]. The remaining two experimental groups demonstrated the same mechanical and metabolic performances on days 1 and 5. Anaerobic performance was not influenced by energy intake and the field course. Blood samples were obtained at rest on days 1 and 5. At the end of CC, the data demonstrated a significant decrease in blood glucose concentrated ion (P〈0.01) for LC diet only. Plasma free fatty acid, blood glycerol and β-OH butyrate were significantly increased in all groups, from day 1, but the values observed for LC were higher than those for the MC and HC diets. The concentrations of the anabolic hormones, insulin and testosterone, decreased in the three groups, the lowest values being observed in the LG group (P 〈 0.05). In conclusion, we found that only a severe energy deficit decreased physical performance during submaximal exercise. A moderate deficit between energy intake and expenditure did not affect performance. Supramaximal exercise did not appear to be influenced by energy intake and CC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00599524
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  • 10
    Electronic Resource
    Electronic Resource
    Lack of coordinated changes in metabolic enzymes and myosin heavy chain isoforms in regenerated muscles of trained rats (2000)
    Springer
    Journal of muscle research and cell motility 21 (2000), S. 269-278 
    Details
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We investigated training-induced changes in biochemical properties and myosin heavy chain (MHC) composition of regenerated (cardiotoxin-injected) plantaris muscles (PLA) in rats either maintained sedentary (S, n = 9) or endurance trained on a treadmill over a 8-week period (T, n = 7). Both endurance training and regeneration altered the pattern of fast MHC expression. An analysis of the two-way interaction between training and regeneration showed that the relative content of type IIa MHC was affected (P 〈 0.05). The 140% increase in type IIa MHC observed in regenerated PLA from T rats compared with nontreated muscle of S rats, exceeded the 102% increase resulting from the combination of regeneration alone (26%) and training alone (61%). A similar interaction between training and regeneration was shown for the percentage of fibres expressing either type IIa or type IIb MHC (P 〈 0.05). In contrast, a significant increase in the citrate synthase (CS) activity was shown in PLA as a result of endurance training, without specific effect of regeneration. Furthermore, training-induced changes in CK and LDH isoenzyme distribution occurred to a similar extent in regenerated and non-treated PLA muscles, and thus did not follow the changes in MHC isoforms. An increase in the mitochondrial CK isozyme activity (mi-CK) was shown in both non-treated and previously degenerated PLA muscles (123 and 117%, P 〈 0.01, respectively), without specific effect of regeneration. The ratio of mi-CK to CS activity, an estimate of the mitochondrial specific activity of mi-CK was significantly increased by training (P 〈 0.02) and decreased by regeneration (P 〈 0.05). Taken together, these data suggest that while training and regeneration have cumulative effects on the pattern of fast MHC expression, the training-induced changes in the energy metabolism shown in mature non-treated myofibres are similar to those observed in regenerated fibres.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005680921792
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