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In order to assess the possible occurrence of acute haemolysis with prolonged exertion, serum haptoglobin levels were determined from venous blood samples collected from eight male runners immediately preceding (PreRH), immediately following (PRH1), and 6 h following (PRH2) completion of a marathon road race. The subjects' mean age, percentage of body fat, and maximum oxygen uptake (VO2max) were 46 +/- 9 years, 12.1 +/- 3.4% and 54.9 +/- 8.4 ml kg-1 min-1, respectively. The mean race finish time for the subjects was 3:35 +/- 0:18 h:min. The PreRH, PRH1 and PRH2 averaged 129 +/-18, 97 +/- 48 and 86 +/- 35 mg dl-1 respectively. Significant differences of -32.5 mg dl-1 between PreRH versus PRH1 and -42.5 mg dl-1 between PreRH versus PRH2 were found. The difference between PRH1 and PRH2 of -10.6 mg dl-1 was not significant. No significant correlations were found between the decreases in serum haptoglobin and VO2max or race finish time. The data suggests to occurrence of an acute haemolysis with performance of the marathon road race. 相似文献
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Timing of ball release in overarm throws affects ball speed in unskilled but not skilled individuals
We tested the hypothesis that variability in the timing of ball release in overarm throws affects ball speed. Nine unskilled and six skilled throwers made 30 throws fast and accurately from a sitting and standing position. Angular positions of finger and arm segments were recorded with search-coils at 1000 Hz; ball speed was measured with a radar gun. The time of ball release from the fingertips was measured with respect to seven arm kinematic reference points. Mean timing windows for ball release were 28 ms for unskilled throwers and 7 ms for skilled throwers. Mixed-model analyses of variance showed that a there was a statistically significant relationship between ball speed and the timing of ball release in unskilled throwers, but not in skilled throwers. This was presumably due to the difference in variability of the timing of ball release between the two groups. In contrast, skilled throwers showed a relationship between ball speed and peak forearm angular velocity (one measure of arm speed). We conclude that although variability in the timing of ball release can affect ball speed, this is only a major factor in unskilled throwers. When skilled throwers throw fast, variability in ball speed is due to variability in arm speed. 相似文献
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