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While deficient exercise performance of sick children results from hypoactivity and detraining, it can also be caused by specific pathophysiological factors. These can affect one or more components of physical fitness. A low maximal aerobic power will result from a low maximal stroke volume, as in aortic stenosis or cardiomyopathy; a low maximal heart rate, as in congenital complete heart block or intake of beta-blockers; a low O2 content of the arterial blood, as in anemia or advanced cystic fibrosis; and a high O2 content of mixed-venous blood, as in muscle atrophy or severe malnutrition. A high O2 cost of locomotion, as in advanced obesity or cerebral palsy, will cause the patient to exert at a high percentage of his maximal aerobic power and thus fatigue easily. A subnormal muscle strength, as in progressive muscular dystrophy or juvenile rheumatoid arthritis, is sometimes the primary factor that limits the walking ability or other daily functions. Recent data suggest that local muscle endurance, as assessed by the Wingate anaerobic test, is particularly deficient in some neuromuscular diseases. Examples are muscular dystrophies and spastic cerebral palsy. The ratio of peak anaerobic power to peak aerobic power seems lower in such patients than in able-bodied controls.
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PMID:Pathophysiological factors which limit the exercise capacity of the sick child. 372 7

Fine wire EMG of the shoulder was performed on 11 swimmers; 5 performed during dry land studies and 7 during aquatic studies. One individual underwent both studies. A cinematographic analysis was synchronized with the EMG data to determine what muscles were firing at each phase of the swim stroke. Eight muscles were studied: biceps, subscapularis, latissimus dorsi, pectoralis major, supraspinatus, infraspinatus, serratus anterior, and deltoid. Three strokes were analyzed: freestyle, breaststroke, and butterfly. The freestyle and butterfly are frequently associated with impingement type syndromes in swimmers. It was determined that the supraspinatus, infraspinatus, middle deltoid, and serratus anterior were predominately recovery phase muscles. The latissimus dorsi and pectoralis major were predominately pull-through phase muscles. The biceps had mixed inconsistent activity during both phases. From dry land quantifications of the EMG signal it was determined that the serratus anterior functions near maximal muscle test during each stroke, and theoretically may fatigue with repetition. It is hoped that a training program aimed to strengthen the scapular rotators may help alleviate impingement syndrome in swimmers.
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PMID:Fine wire electromyography analysis of muscles of the shoulder during swimming. 375 49

This investigation was undertaken in patients who had an acute myocardial infarction 12.6 +/- 0.4 months earlier to determine, using conventional methods, the nature of stroke volume changes during training regimens. Twenty-seven patients (mean age 52 +/- 2 years; rest ejection fraction 49 +/- 2%; New York Heart Association functional class I or II) and 9 normal, age-matched sedentary control subjects (mean age 50 +/- 1 years) exercised in the upright position on a bicycle ergometer. Stroke volume was measured by impedance cardiography at rest and after each workload. Ten patients (group A) had a stroke volume response similar to that of the normal sedentary subjects. In 8 patients (group B) the stroke volume increased initially, then decreased (more than 15%) at heart rates (HRs) greater than 100 to 105 beats/min. Nine patients (group C) had a flattened stroke volume response throughout exercise. Training HR determined by conventional methods corresponded to a maximal stroke volume in the normal subjects. Training HR in group A corresponded to a stroke volume that was maximal or near-maximal. Training HR in group B corresponded to a maximal or diminishing stroke volume. In group C, the training HR corresponded to a stroke volume no different from that at rest. Thus, training HR determined by conventional methods based solely on the chronotropic responses to exercise may place patients who have abnormal stroke volume responses to upright exercise in a situation during training sessions in which an inappropriately high HR, excessive fatigue or silent ischemia may develop.
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PMID:Importance of considering ventricular function when prescribing exercise after acute myocardial infarction. 377 45

Central and peripheral cardiovascular adaptations to 12 weeks of intense swim training were characterized in 12 previously sedentary middle-aged men and women. Peak oxygen uptake (VO2) during upright bicycle exercise improved from 29.2 +/- 5.6 to 34.7 +/- 6.7 ml/kg/min (mean +/- SD, p less than .01) because of similar increases in peak cardiac output (CO) and calculated arteriovenous oxygen difference (both p = .02). Peak supine VO2 was 10% higher after training (p less than .005) solely because of enhanced CO (p = .005). Peak heart rate decreased in both postures; therefore stroke volume at peak exercise was greater by 10% and 18% in the upright and supine postures, respectively (p = .05 and p = .005). There was an identical 18% rise (p = .01) in peak supine left ventricular end-diastolic volume index by radionuclide ventriculography but no change in left ventricular ejection fraction or end-systolic volume index (ESVI). Peak systolic blood pressure (SBP) was unchanged in the upright posture but was 8% higher (p = .002) during recumbency despite a similar total peripheral resistance and SBP/ESVI ratio. Maximal calf conductance (Gmax), assessed separately by venous occlusion plethysmography after local ischemic exercise to fatigue, was augmented 20% (p less than .02) by training, resulting in an 18% greater hyperemic blood flow (p = .05). Peak VO2, CO, and Gmax were unchanged in five nonexercising control subjects. We conclude that in middle-aged humans, intense swim training for 12 weeks produces adaptations that include a greater capacity for vasodilatation in skeletal muscle and an enhanced cardiac pump capacity.
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PMID:Cardiovascular adaptations to intense swim training in sedentary middle-aged men and women. 380 36

The hemodynamic response to static exercise in 28 patients with congestive heart failure (CHF) was compared with that in 8 control subjects. Static handgrip exercise at 50% of the maximal voluntary contraction was performed to fatigue. In patients with CHF, pulmonary arterial wedge pressure increased from 20 +/- 18 to 31 +/- 10 mm Hg (p less than 0.001) (mean +/- standard deviation) and systemic vascular resistance increased from 1,730 +/- 454 to 2,151 +/- 724 dynes s cm-5 (p less than 0.001). Although cardiac index did not change significantly, stroke volume index and stroke work index decreased from 24 +/- 6 to 20 +/- 6 ml/m2 (p less than 0.001) and 28 +/- 11 to 25 +/- 12 g-m/s2 (p less than 0.05), respectively. In control subjects, pulmonary arterial wedge pressure did not change significantly; cardiac index increased from 3.6 +/- 0.3 to 4.0 +/- 0.4 liters/min/m2 (p less than 0.05) and systemic vascular resistance increased slightly, from 1,011 +/- 186 to 1,106 +/- 180 dynes s cm-5 (p less than 0.05). The effects of arterial dilation with hydralazine on the response to static exercise were assessed in 10 of the patients with CHF. Compared with predrug exercise, cardiac index increased 68% (p less than 0.01), stroke volume index increased 76% (p less than 0.01) and systemic vascular resistance decreased 47% (p less than 0.01) after administration of hydralazine. Thus, static exercise can have adverse effects on cardiac performance in patients with CHF.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Static exercise with congestive heart failure and the response to vasodilating drugs. 381 18

The purpose of this study was to examine the central and peripheral hemodynamic adaptations to maximal leg extension exercise. Seventeen men (X = 25 years, 84 kg) performed leg extension exercise (Universal equipment) for 12 repetitions (90s) to fatigue. Each repetition consisted of a 3s lifting motion, 1s pause, and 3s lowering motion. Impedance cardiography was used to measure stroke volume (SV), cardiac output (Q), systolic time intervals, and impedance contractility indices on a beat-by-beat basis. There were significant increases in systolic, diastolic, mean arterial pressure, total peripheral resistance, and HR during exercise. The mean Q remained similar throughout the protocol. SV decreased even though indices of myocardial performance indicated an enhancement of contractility. The magnitude of Q and SV were dependent upon the phase of leg extension. SV and Q during the lifting portions of the exercise were smaller than the lowering portions. The differences in SV and Q during the concentric and eccentric phases of the exercise most likely reflect the large static forces in exercising muscle which impeded venous return and increased afterload.
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PMID:Central and peripheral hemodynamics during maximal leg extension exercise. 383 Jan 35

This chapter has reviewed some of the methodological and theoretical issues in research linking the social environment to medical illnesses. The second part of the chapter has focused on three specific neurological entities to examine evidence for a possible association between neurological illness and life stress. There is some suggestion that certain vulnerable epileptic patients can experience convulsions in response to acute emotional upheaval or certain types of cognitive challenges. More commonly, it is probable that social stress and emotional tension can produce lowering of seizure threshold by increasing levels of fatigue and disrupting sleep. The latter factor, in particular, is known to lower seizure threshold. In the case of stroke, several dramatic cases of intracranial hemorrhage have been related to disastrous life circumstances. A general association between life stress and stroke has yet to be established. The case for a link between life events and onset of exacerbation of multiple sclerosis seems stronger. Events which produce emotional upset seem capable of worsening symptoms in patients with existing disease, and several studies have reported unusual life stresses in the period preceding onset of symptoms in this disorder.
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PMID:The social environment and neurological disease. 389 69

The impact of exhaustive exercise on myocardial function is poorly understood. Experimental parameters of contractility that are completely devoid of other influences do not exist. Furthermore, the problem is compounded by the fact that exhaustive work comprises myriad exercise paradigms and fatigue may be the result of numerous possible mechanisms. Despite these confounding variables, there is evidence that stroke volume may be impaired by prolonged work in humans. These studies implicated reduced venous return and not contractility as the reason. Experiments with the rat model have indicated that treadmill running at about 60% of VO2max results in reduced isometric twitch tension in isolated trabecular tissue. The data are consistent with the notion that contractility is substantially reduced. The mechanism for this inhibition is unknown. In separate studies using a similar model, it has been shown that Ca2+ uptake by the sarcoplasm reticulum of the myocardium in vitro is reduced by fatigue. It is conceivable that in exhaustive exercise, there may be only a slight effect on contractility in vivo but that substantial adjustments in intracellular homeostasis are required in order to achieve this. Future considerations should include a rigorous analysis of contractility and the factors that regulate it, as well as the choice of animal and exhaustion models.
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PMID:Regulation of myocardial contractility in exhaustive exercise. 390 42

Although Doppler echocardiography is useful in the assessment of left ventricular function at rest, little information is available on the application of this technique during exercise. Consequently, Doppler aortic flow studies were performed in 17 young normal subjects during and after supine bicycle exercise. The purposes of the study were to determine the feasibility of recording Doppler aortic flow velocity with a suprasternal notch transducer during exercise and to assess the changes in normal aortic flow velocity parameters during exercise and early recovery. Each subject exercised until fatigue; mean duration of exercise was 10 minutes. Heart rate increased from a mean of 69 beats/min at control to 159 beats/min at peak exercise. On average, aortic peak flow velocity increased by 45% from control, reaching its maximum at 2 minutes after exercise. Ejection time decreased by 34% during exercise, being shortest at peak exercise. Heart rate, peak flow velocity and ejection time had not returned to normal by 10 minutes after exercise. Aortic flow velocity integral (a relative measure of stroke volume) decreased by 10% at peak exercise (p less than 0.05) compared with control, but had returned to control at 2 minutes after exercise. Despite mild aliasing, increased spectral dispersion, faster heart rates and increased respiratory rate during maximal exercise, aortic flow velocity measurements could be recorded using the suprasternal technique. These baseline Doppler exercise data should be useful in further studies of exercise hemodynamic changes in patients with heart disease.
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PMID:Studies of Doppler aortic flow velocity during supine bicycle exercise. 394 24

The mean velocity of 9 out of 10 women's events during the U.S. Olympic Swimming Trials was greater in 1984 as compared to 1976. Three of the 10 men's events showed improvement. In 9 out of these 12 events, the increased velocity was accounted for by increased distance per stroke (range, -3 to -13%). In the women's 100-m butterfly and 100-m backstroke, increased velocity was due solely to faster stroke rates. The finalists in each event were compared to those whose velocities were 3-7% slower. In almost all events and stroke styles, the finalists achieved greater distances per stroke than did the slower group. In the men's events increased distance per stroke was associated with decreased stroke rate, except in the backstroke, in which both were increased for the finalists. Although the faster women swimmers generally had greater distances per stroke, they were more dependent than men on faster stroke rates to achieve superiority. The profile of velocity for races of 200 m and longer indicated that as fatigue developed the distance per stroke decreased. The faster swimmers compensated for this change by maintaining or increasing stroke rate more than did their slower competitors. This study indicates that improvements and superiority in stroke mechanics are reflected in the stroke rate and distance per stroke used to swim a race.
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PMID:Velocity, stroke rate, and distance per stroke during elite swimming competition. 407 32


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