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Query: UMLS:C0015672 (fatigue)
 51,768 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Maximal aerobic capacity of 66 ten year old ice hockey players was measured on a treadmill twice over a 4 to 5 month period. This time approximated mid (T1) to post (T2) competitive season. The results of these VO2 max tests were grouped according to the presence or absence of a plateau in the oxygen uptake (less than 2.1 ml/kg-min) during the last work loads before fatigue. The mean values for T1 and T2 were not significantly different for any of the measurements made; the reproducibility was considered to be high. The reliability of the measures varied with the presence or absence of a plateau at maximum, for example; VO2 max, plateau r = 0.74, no plateau r = 0.27; heart rate, plateau r = 0.92, no plateau r = 0.40. The differences between the mean values for the "double plateau" group when compared to the "no plateau" group were not significant for VO2 max, HR or VE. The differences were significant for the post-exercise blood lactate and respiratory exchange values at T2 only; the "double plateau" group reached higher values in each case (R = 1.00 vs 0.92; blood lactate 6.5 vs 5.4 mM/1).
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PMID:Reliability and reproducibility of maximal oxygen uptake measurement in children. 89 25

We examined the effect of O2-enriched air upon performance capacity and some physiological and psychological variables. Eight firemen were studied during seven bouts of 2 min treadmill-running while breathing air with 21 or 40% oxygen. The duration of the resting periods between the working bouts was chosed by the subjects themselves, with the instructions to rest as short as possible. Total resting time decreased by 29% and total amount of air used by 6%, under the 40% oxygen condition. There were no differences in 1) minute ventilation during working periods (when the subjects breathed 40% oxygen respiratory rate decreased whereas tidalvolume increased), 2) heart rate reached during working periods, 3) subjective feelings of fatigue as indicated by the subjects at the end of every working period. Advantages of the use of O2-enriched air by firemen are discussed and it is concluded that breathing air with 40% oxygen does not mean an extra physiological or psychological load for the organism. Finally, possible factors that made a subject decide to start again are discussed and the importance of the respiratory rate in this decision is indicated.
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PMID:Effect of hyperoxia on performance capacity of firemen. 90 49

Two divers spent over 50 hours at 610 msw in a helium-oxygen mixture (PO2:0.38-0.52 ATA). The dive duration was 27 days, including predive stages of confinement, compression, time at maximum pressure, and decompression. The divers were asked to answer 30 questions on their feelings of mental and physical fatigue and to indicate on a nine-point scale their estimation of a general feeling of fatigue. Subjective feelings of fatigue reported in this dive suggested that the divers were in good condition. Hyperbaric arthralgia and physical complaints were reported, especially during decompression, with some postdive persistence, but they should be considered as distinct signs of feelings of fatigue. The critical flicker frequency (CFF), measured throughout the dive for the two divers, showed systematic variations and a relationship between compression and pressure. These variations were grossly parallel to EEG modifications reported in other studies and probably reveal neurophysiological troubles that were not apparent from subjective reports.
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PMID:Critical flicker frequency (CFF) and subjective fatigue during an oxyhelium saturation dive at 62 ATA. 96 26

1 Thirteen men with untreated essential hypertension in WHO stage I were studied on an outpatient basis to evaluate the haemodynamic long-tern effect of a new beta-adrenoceptor blocker, atenolol. 2 Oxygen consumption, heart rate, cardiac output (Cardiogreen) and intraarterial branchial pressure were recorded at rest in a supine and sitting position and during steady state work at 300, 600 and 900 kpm/min. 3 The subjects were treated with atenolol (dose 100-200 mg/day) as the sole drug for 1 year and the haemodynamic study was repeated. 4 The blood pressure was reduced approximately 18% both at rest and during exercise, the heart rate approximately 25% and the cardiac output 16% at rest supine and 27% at rest sitting. During exercise the reductions in cardiac output were approximately 20%. The calculated total peripheral resistance was not decreased compared to pretreatment values. The mean arterial pressure-heart rate product was reduced almost 40%. 5 Apart from temporary muscular fatigue during the first weeks, no side-effects were seen. 6 Atenolol is an effective blood pressure lowering drug in mild and moderate hypertension, but the drop in blood pressure is associated with marked reduction in heart rate and cardiac output at rest as well as during exercise.
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PMID:Haemodynamic long-term effects of a new beta-adrenoceptor blocking drug, atenolol (ICI 66082), in essential hypertension. 97 71

Rat hepatocytes were isolated by liver perfusion in the presence of collagenase and hyaluronidase and incubated in the absence or presence of oxygen. As a result of anoxia, there was a gradual increase in plasma membrane permeability, noted as an increase in succinate-stimulated oxygen uptake, a decrease in trypan blue exclusion frequency, a leakage of cytosolic lactate dehydrogenase activity and an increased proportion of swollen and disrupted cells. After anaerobic incubation for 30 minutes--but not for 60 minutes--there were signs of recovery from anoxic cell injury upon re-oxygenation. The changes in plasma membrane permeability properties in anoxia seemed to be preceded by a marked decrease in cellular ATP level; aerobic incubation of hepatocytes in the presence of an uncoupler of phosphorylation from respiration led to a similar decrease in cellular ATP concentration followed by similar disturbances in plasma membrane permeability properties. It is suggested that a distrubed plasma membrane function caused by a decreased energy level is of primary importance for the initiation of cell death in anoxia.
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PMID:Isolated rat hepatocytes as an experimental tool in the study of cell injury. Effect of anoxia. 100 75

One-arm cranking was done by ten healthy male adults at an oxygen intake level of about 1.0 liter/min. Each subject performed two kinds of cranking at a speed of 60 rpm: forced cranking using only one arm continuously for 15 min and free cranking for 30 min with the instructions to alternate from one arm to the other whenever fatigue set in. The results, excluding those of a subject who changed arms very frequently, were analyzed. In forced cranking, oxygen intake and heart rate steadily increased, the average time of appearance of local fatigue being 161 sec for the stronger arm and 122 sec for the weaker one. In free cranking, the working arm was changed 6 to 23 times during the 30-minute period, while oxygen intake and heart rate increased with fluctuations. The mean duration interval was 175 sec with the stronger arm and 123 sec with the weaker one. The mean interval of arm alternation was positively correlated with the individual time of onset of the sensation of local rigidness during forced cranking, but not with the individual time of initiation of respiratory distress. It is suggested that alternation of active muscles in moderately dynamic work may be linked with an early stage of local fatigue which is different from that of static work.
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PMID:Spontaneous alternation of the working arm in one-arm cranking. 103 Jul 31

Estimation of lactate oxidation in vivo was carried out by a tracer technique in the muscles of the lower hindleg of the dog during tetani of different duration. The fractional (%) rate of lactate oxidation increased markedly, compared with that of the resting muscle, after the first 2 min of stimulation. Lactate oxidation afforded a large contribution to the total oxygen consumption. Fatigue appeared to play a role in limiting lactate oxidation in the later phase of sustained contraction.
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PMID:Lactate oxidation by skeletal muscle during sustained contraction in vivo. 103 26

In excised, curarized and massively stimulated fast-twitch mouse gastrocnemius muscles the early twitch tension enhancements (treppe) during 1/s activity between 10 and 36 degrees C increase and affect more contractions as temperature increases. Tension output eventually declines at a temperature-independent rate. Half-relaxation time lengthens below 25 degrees C and shortens above 25 degrees C. During 1/0.63s twitches half-relaxation time lengthens even at 25 degrees C. In slow-twitch soleus muscles activity decreases twitch tension and half-relaxation time regardless of temperature. Activity shortens contraction times in both muscles. Oxygen lack induced by NaN3 cannot account satisfactorily for these results. Activation is apparently more plastic in the gastrocnemius than in the soleus, and the relationship between the rates of their activation and relaxation processes and the temperature sensitivities of these rates also seem to differ. In both muscles caffeine can convert activity-induced shortened of half-relaxation times into prolongations. In the soleus this effect is more pronounced at 30 than at 25 degrees C. At high temperature and twitch rates caffeine reduces treppe amplitude and duration without affecting the eventual twitch tension decline in the gastrocnemius while it greatly accelerates twitch tension decline in the soleus. In both muscles intrafiber Ca2+ movements are apparently major determinants of fatigue behavior.
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PMID:Fatigue and caffeine effects in fast-twitch and slow-twitch muscles of the mouse. 103 14

Eight experimental subjects from the USAF Sschool of Aerospace Medicine (SAM) and four YF-16/17 test pilots were exposed to a simulated aerial combat maneuver (SACM) which included a maximum G exposure of 6 s at 8 G. The following physiologic parameters were examined relative to seatback angles of 23degrees, 28degrees, and 40degrees; heart rate and rhythm; arterial oxygen saturation; performance; intrathoracic (esophageal) pressure; arterial pressure; and subject comfort, effort, and fatigue. Relaxed and straining high sustained G (HSG) tolerances (6 G for 60 s) were also determined using only SAM subjects. The advantages of the 40 degree setback angle during the SACM included increased subject comfort, less fatigue and effort, greater pilot acceptance and a statisically significant reduction in the increased mean heart rate associated with G exposure. On the other hand, a statistically significant reduction in arterial oxygen saturation was obtained during the SACM at 40 degrees compared with the 23 degree back angle. An increase in relaxed G tolerance was found with the 40degree seatback angle--statistically significant only compared with the 28 degree seatback angle.
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PMID:Physiologic effects of seatback angles 45degrees (from the vertical) relative to G. 115 99

This study has shown that repetitive exchanges between the American Apollo space vehicle atmosphere of 100% oxygen at 5 psia (258 torr) and the Russian Soyuz spacecraft atmosphere of 30% oxygen-70% nitrogen at 10 psia (523 torr), as simulated in altitude chambers, will not likely result in any form of decompression sickness. This conclusion is based upon the absence of any form of bends in seven crewmen who participated in 11 tests distributed over three 24-h periods. During each period, three transfers from the 5 to the 10 psia environments were performed by simulating passage through a docking module which served as an airlock where astronauts and cosmonauts first adapted to each other's cabin gases and pressures before transfer. Biochemical tests, subjective fatigue scores, and the complete absence of any form of pain were also indicative that decompression sickness should not be expected if this spacecraft transfer schedule is followed.
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PMID:Prevention of decompression sickness during a simulated space docking mission. 115 3


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