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

Dyspnea, leg effort (Borg 0 to 10 scale), ventilation, and heart rate (VEmax/VEcap; HRmax/HRcap expressed as a percentage of capacity) were measured at maximal exercise (cycle ergometer) in 97 patients with chronic airflow limitation (CAL) (FEV, 46.6 +/- 14.23% of predicted) and compared with 320 matched control subjects. Patients with CAL achieved a maximum power output of 86 +/- 39.5 W (60 +/- 23.2% of predicted) compared with 140 +/- 37.5 W (98 +/- 14.5% of predicted) in controls (p less than 0.0001), VEmax/VEcap was 72 +/- 19.3% compared with 53 +/- 18.6% (p less than 0.0001), and HRmax/HRcap was 76 +/- 13.5% compared with 82 +/- 13% (p less than 0.001). These findings were expected. The median intensity of dyspnea was 6 (severe to very severe) and leg effort was 7 (very severe) in both groups, and these findings were unexpected. The patients with CAL were handicapped by an increase in both dyspnea and peripheral muscular effort relative to the actual power output. The rating of dyspnea exceeded leg effort in 25 (26%) of CAL versus 69 (22%) control subjects: the rating of leg effort exceeded dyspnea in 42 (43%) CAL and 117 (36%) control subjects; both were rated equally in 30 (31%) CAL and 134 (42%) control subjects, respectively (NS). VEmax/VEcap and HRmax/HRcap were not significantly different in those limited by dyspnea, leg fatigue, or a combination of both. All values are expressed +/- SD.
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PMID:Exercise capacity and ventilatory, circulatory, and symptom limitation in patients with chronic airflow limitation. 836 56

The physiological characteristics of 32 elite Canadian synchronized swimmers were studied. The variables examined included aerobic power (VO2 max), anaerobic power measured by a maximal 30 second effort on a bicycle ergometer (AN30) and pulmonary function including forced vital capacity (FVC) and forced expiratory volume in one second (FEV 1.0). As a group, they were superior to non-athletic (untrained) women in VO2 max, with a mean of 44.4 ml . kg-1 . mon-1 or 2.39 l . min-1 but lower than competitive women swimmers of similar age. FVC and FEV 1.0 values were also higher than non-athletes and lower than competitive swimmers. AN30 was unremarkable, being identical to that of non-athletes. Comparisons were made between junior and senior competitors and between the 2 senior teams that made up the Canadian national team. Correlations between the athletes' performance scores in the 1977 Canadian national championships and VO2 max, AN30, FVC amd FEV 1.0 failed to yield any significant relationships. However, VO2 max in ml . kg-1 . min-1 related to solo performance scores was very close to the accepted level of significance (r = .41, p = 06). Precision techniques and skills are undoubtedly of major importance in this sport. However, a level of aerobic power sufficient to prevent fatigue during a performance and to allow long hours of training on technique would be prudent.
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PMID:Physiological characteristics of elite synchronized swimmers. 744 27

In patients with chronic obstructive pulmonary disease (COPD) the intensity of aerobic training is limited by dyspnea. Improving strength of the inspiratory muscles could enhance aerobic exercise training by reducing exercise-related dyspnea. We examined effects of home-based inspiratory muscle training (IMT) and cycle ergometry training (CET) in 53 patients with moderate to severe COPD (FEV(1)% pred, 50 +/- 17 [mean +/- SD]). Patients were randomly assigned to 4 mo of training in one of four groups: IMT, CET, CET + IMT, or health education (ED). Patients were encouraged to train to the limits of their dyspnea. Inspiratory muscle strength and endurance increased in IMT and CET + IMT groups compared with CET and ED groups (p < 0. 01). Peak oxygen uptake increased and heart rate, minute ventilation, dyspnea, and leg fatigue decreased at submaximal work rates in the CET and CET + IMT groups compared with the IMT and ED groups (p < 0. 01). There were no differences between the CET and CET + IMT groups. Home-based CET produced a physiological training effect and reduced exercise-related symptoms while IMT increased respiratory muscle strength and endurance. The combination of CET and IMT did not produce additional benefits in exercise performance and exercise-related symptoms. This is the first study to demonstrate a physiological training effect with home-based exercise training.
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PMID:Cycle ergometer and inspiratory muscle training in chronic obstructive pulmonary disease. 1043 Jul 20

Patients with chronic obstructive pulmonary disease (COPD) are at a mechanical disadvantage and should be predisposed to the development of diaphragmatic fatigue when the ventilatory system is stressed by exercise. The purpose of this study was to determine whether patients with moderately severe COPD develop contractile fatigue of the diaphragm after cycle exercise to the limits of tolerance. Twelve male patients with COPD, age 61.4 +/- 3.0 yr, participated. Their forced expiratory volume in 1 s (FEV(1)) was 1.79 +/- 0.14 L, 49.6 +/- 3.4% of predicted. Patients cycled at 60-70% of their predetermined maximal work capacity until they had to stop because of intolerable symptoms. Twitch transdiaphragmatic pressure (Pdi,tw) was measured during cervical magnetic stimulation before and 10, 30, and 60 min after exercise. A persistent fall in Pdi,tw postexercise of >/= 10% was considered potentially indicative of contractile fatigue of the diaphragm. Patients cycled for 10.2 +/- 2.0 min at a workload of 59.9 +/- 4.3 W. Patients exercised maximally relative to their capacity reaching a peak oxygen consumption (V O(2)) of 108.1 +/- 2.8% of the peak V O(2) obtained during a preliminary maximal incremental exercise test. Pdi,tw was not significantly different from baseline at any time postexercise. Pdi,tw was 19.9 +/- 1.6 cm H(2)O at baseline, 19.6 +/- 2.0 cm H(2)O at 10 min postexercise, 18. 6 +/- 2.0 cm H(2)O at 30 min postexercise, and 19.5 +/- 1.7 cm H(2)O at 60 min postexercise. In the individual patients, two of the patients had a persistent >/= 10% fall in Pdi,tw postexercise, potentially indicative of contractile fatigue of the diaphragm. In conclusion, the majority of patients with moderately severe COPD do not develop contractile fatigue of the diaphragm after high-intensity constant workload cycle exercise to the limits of tolerance.
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PMID:Diaphragmatic fatigue and high-intensity exercise in patients with chronic obstructive pulmonary disease. 1061 7

Patients with COPD have derangements in respiratory mechanics that may cause them to stop exercising before the exercising limb muscles reach their functional limits. However, because lung disease makes activity unpleasant, patients with chronic obstructive pulmonary disease (COPD) often adapt a sedentary lifestyle leading to progressive deconditioning. Deconditioning will lead to progressive deterioration in limb muscle function, which could adversely affect exercise capacity. The purpose of this study was to determine whether fatigue of the quadriceps muscle occurs after high intensity cycle exercise to the limits of tolerance in patients with moderate to severe COPD. Nineteen male patients with COPD (FEV(1) 1.54 +/- 0. 12 L; 42 +/- 3% predicted) exercised at 60 to 70% of their predetermined maximal work capacity until exhaustion. The femoral nerve was supramaximally stimulated with a figure-of-eight magnetic coil, and quadriceps twitch force (TwQ) was measured before and at 10, 30, and 60 min postexercise. Patients exercised at 53.7 +/- 4.1 watts for 10.4 +/- 1.4 min. Peak V O(2) was 1.24 +/- 0.08 L/min (51. 3 +/- 3.6% predicted). TwQ fell significantly postexercise; 79.2 +/- 5.4% of baseline value at 10 min postexercise (p < 0.005), 75.7 +/- 4.8% at 30 min postexercise (p < 0.001), and 84.0 +/- 5.0% at 60 min postexercise (p < 0.005). Acceptable M-waves from the quadriceps muscle (not obscured by stimulus artifact) were obtained in six subjects. M-wave amplitude was unchanged from baseline at all times postexercise indicating that the fall in TwQ was due to contractile fatigue and not to transmission failure. In conclusion, contractile fatigue of the quadriceps muscle occurs after high intensity cycle exercise to the limits of tolerance in patients with COPD.
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PMID:Quadriceps fatigue after cycle exercise in patients with chronic obstructive pulmonary disease. 1067 84

If chronic hypercapnia in patients with severe COPD occurs as a consequence of respiratory muscle (RM) weakness or fatigue, we would expect that ventilatory muscle recruitment (VMR) and exercise performance in stable hypercapnic patients would differ from those in eucapnic patients. We evaluated exercise performance and RM function at rest and during exercise in 19 eucapnic (PCO(2) 40 +/- 3 mm Hg), and 13 hypercapnic (PCO(2) 52 +/- 10 mm Hg) patients with severe COPD. A metabolic cart was used to determine V E, V O(2), V CO(2), and HR. Gastric (Pg) and esophageal (Ppl) balloons were used to measure Pg, Ppl, and Pdi. Ventilatory muscle recruitment pattern (VMR) was partitioned using end-inspiratory and end-expiratory Pg and Ppl. Hypercapnic patients had lower FEV(1) (0.60 +/- 0.24 versus 0.95 +/- 0.31 L, p < 0.001), MVV (28 +/- 11 versus 41 +/- 13 L, p < 0.001), resting PO(2) (61 +/- 11 versus 70 +/- 11 mm Hg, p < 0.001), peak PO(2) (60 +/- 20 versus 75 +/- 22 mm Hg, p < 0.005), and V E(max) (24 +/- 10 versus 32 +/- 12 L/min, p < 0.001). Patients in both groups had similar FRC (5.7 +/- 1.6 versus 5.0 +/- 1.5 L), V O(2)max (0.58 +/- 0.30 versus 0.76 +/- 0.32 L/min), Watts (45 +/- 48 versus 71 +/- 59), V E/MVV (88 +/- 33 versus 79 +/- 14), and HRmax (117 +/- 17 versus 128 +/- 18 beats/min). PI(max) (67 +/- 28 versus 65 +/- 32 cm H(2)O) and PE(max) (98 +/- 34 versus 96 +/- 40 cm H(2)O) were also similar in both groups. VMR (DeltaPg/DeltaPpl) at rest (-0.28 +/- 0.51 versus 0 +/- 0.35) and during exercise (0.4 +/- 0.2 versus 0.39 +/- 0.15) was equally affected in both groups. We conclude that exercise capacity and ventilatory muscle recruitment are similarly impaired in eucapnic and hypercapnic patients with severe COPD. These findings make inability of the lung to increase ventilation and not respiratory muscle dysfunction a more attractive explanation for CO(2) retention in stable hypercapnic patients.
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PMID:Respiratory muscle recruitment and exercise performance in eucapnic and hypercapnic severe chronic obstructive pulmonary disease. 1071 37

We have recently shown that patients with chronic obstructive pulmonary disease (COPD) develop contractile fatigue of their quadriceps muscle following endurance exercise. Pulmonary rehabilitation can produce physiological adaptations in patients with COPD. We hypothesized that if pulmonary rehabilitation induces physiological adaptations in the exercising muscle, it should become more fatigue resistant. Twenty one patients with COPD, mean age 69.9 +/- 1.9 yr, FEV(1) 45 +/- 4% predicted, participated in an 8-wk outpatient, supervised pulmonary rehabilitation exercise program. Quadriceps contractile fatigue was detected by a fall in quadriceps twitch force postexercise. Twitch force was measured during magnetic stimulation of the femoral nerve. Because potentiated twitches may be more sensitive at detecting fatigue, both unpotentiated (TwQu) and potentiated (TwQp) twitches were obtained before and 10, 30, and 60 min after constant load cycle exercise. Prerehabilitation, during constant load exercise, patients exercised at 37 +/- 4 W for 11.2 +/- 1.8 min. Prerehabilitation, TwQu fell significantly postexercise down to a minimum value of 82.5 +/- 3.1% of the baseline preexercise value (p < 0.001). Similarly, prerehabilitation, TwQp fell significantly postexercise down to a minimum value of 73.9 +/- 3.9% of baseline (p < 0.001). Postrehabilitation, for the same intensity and duration of exercise, TwQu was not significantly different from baseline at any time postexercise. Postrehabilitation, TwQp fell significantly postexercise but the fall in TwQp with exercise was significantly less postrehabilitation compared with prerehabilitation (p < 0.001). In conclusion, pulmonary rehabilitation resulted in increased fatigue resistance of the quadriceps muscle in patients with COPD.
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PMID:Effect of pulmonary rehabilitation on quadriceps fatiguability during exercise. 1128 68

The impact of noninvasive positive-pressure ventilation (NIPPV) on pulmonary function studies, quality of life, and survival was assessed in patients with amyotrophic lateral sclerosis. NIPPV did not change the rate of decline of the forced vital capacity (FVC) and forced expiratory volume in the first second (FEV(1)) (2.31 and 2.09 percent-predicted points per month, respectively). NIPPV resulted in a drop of FEV(1) by 5.94 percent-predicted points (P = 0.07), and of maximal inspiratory pressure by 6.33 percent-predicted points (P = 0.11). The change in FEV(1) and FVC pre- and postintervention correlated with the corresponding change in maximal inspiratory pressure. Fatigue and mastery scores were improved by NIPPV. Median survivals in patients intolerant and tolerant of NIPPV were 5 and 20 months, respectively (P = 0.002). Although NIPPV has no impact on the rate of decline of lung function and may have deleterious effects on spirometric measures, it may improve quality of life and survival.
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PMID:Objective measures of the efficacy of noninvasive positive-pressure ventilation in amyotrophic lateral sclerosis. 1135 27

One of the mechanisms proposed to explain the decrement in pulmonary function often seen after exercise is fatigue of the expiratory muscles. To test the hypothesis that expiratory muscle fatigue alters lung function, several indices of pulmonary function were measured before and after expiratory muscle fatigue was induced by expiratory loaded breathing. Eight subjects completed a fatigue trial (EF) in which expiratory threshold loaded breathing was performed at an initial resistance equal to 80 % of their maximal expiratory pressure (MEP), at a respiratory rate of 13 bpm, and a duty cycle (T(I)/T(Tot)) of 0.33. MEP was taken at predefined intervals throughout the loaded breathing protocol, and loaded breathing was discontinued when MEP was less than 80 % of each subject's pre EF trial MEP (T(Lim)). FVC, FEV(1.0), FEF(25 %), FEF(25-75 %), and maximal inspiratory and expiratory pressures (MIP and MEP) were taken prior to, immediately after, and at 5, 10, and 15 min post fatigue. On a separate day a control trial (CON) was performed that was identical to each subjects EF trial with the exception that no expiratory load was utilized. At T(Lim) MEP was significantly reduced (p < 0.001) by 23.5 % from the pre-expiratory loaded breathing value (183.1 +/- 39.56 to 140.13 +/- 30.45 mmHg), whereas it remained unchanged during the CON trial (191.06 +/- 44.18 to 188.06 +/- 43.50 mmHg). FVC measured prior to and immediately after T(Lim) remained unchanged following both the EF (5349.45 +/- 1130.8 to 5387.43 +/- 1139.92 mL) and CON trials (5287.75 +/- 1220.29 and 5352.78 +/- 1191.30 mL). These results suggest that any expiratory muscle fatigue developed during exercise by itself does not result in altered pulmonary function. However, any interactions between expiratory muscle fatigue and other consequences of exercise that may alter lung function cannot be ruled out.
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PMID:Pulmonary function subsequent to expiratory muscle fatigue in healthy humans. 1159 Apr 76

Lung hyperinflation is a consequence of airway obstruction, increased airway resistance and compliance in patients with chronic obstructive pulmonary disease (COPD) which may result in respiratory muscle fatigue and deterioration of gas transfer. The aim of this study was to investigate the influence of hyperinflation on respiratory muscles, gas transfer and breathing pattern and compare the differences between mild and severe COPD. Twenty-eight COPD patients with radiological and tomographic evidence of emphysema were included in the study and they were divided into two groups according to the severity of COPD. Group I= FEV(1) < or = 49% (n= 16). Group II= FEV(1) > or = 50% (n= 12). Airflow rates were decreased and airway resistance was increased significantly in Group I. Maximal inspiratory pressure (MIP) was significantly reduced in Group I. FRC, RV and RV/TLC ratio were increased above 120% in both groups with more significant increase in Group I. Group I showed moderate hypoxemia (PaO(2) = 54.02 mmHg) with hypercapnia (PaCO(2)= 46.65 mmHg) whereas Group II patients were mildly hypoxemic (PaO(2)= 63.78 mmHg) with normocapnia. Parameters of breathing pattern were similar in both groups. Diaphragm height index (DHI) didn't showed significant difference between groups. But there were significant correlations between DHI and RV, FRC. MIP showed significant positive correlation with airflow rates and DLCO, negative correlation with lung volumes, positive correlation with PaO(2) and negative correlation with PaCO(2). FRC also negatively correlated with Ti and Ti/Ttot. In conclusion, hyperinflation present even in the mild forms of COPD causes inspiratory muscle weakness which in return results in impairment in gas transfer.
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PMID:[The effect of hyperinflation on respiratory muscles and breathing pattern in COPD]. 1514 1


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