Background:We previously reported that the occurrence of contractile fatigue of the quadriceps during exercise in patients with COPD reduced the likelihood of acute bronchodilation to improve the endurance time to constant work rate exercise. The purpose of the present study was to assess whether the perception of dyspnea and leg fatigue during exercise could be used to predict the exercise response to acute bronchodilation in this population. Methods: Sixty-eight patients with COPD performed either two constant work-rate cycling exercises or two endurance shuttle walking tests. These tests were preceded by nebulization of placebo or 500 mg ipratropium bromide. Changes in FEV1 and in the endurance time with bronchodilation were measured. The changes in quadriceps twitch force after exercise were evaluated. In addition, we assessed dyspnea and perception of leg fatigue on Borg scale as well as the locus of exercise limitation (dyspnea, leg fatigue, or both). Results: The locus of symptom limitation was useful to predict the exercise response to bronchodilation; patients stopping exercise because of leg fatigue or due to a combination of dyspnea/leg fatigue showed a smaller improvement in endurance time to constant work rate exercise with bronchodilation compared with those stopping because of dyspnea. Subjective and objective evidences of fatigue were related: patients who stopped exercising because of leg fatigue showed a larger fall in quadriceps twitch force compared to patients who stopped for dyspnea. Conclusion:The assessment of the locus of symptom limitation during constant work rate exercise is useful to predict the improvement in endurance time following acute bronchodilation in patients with COPD. Individualized Intervention Model Background:The goal of the present study was to compare the maximum walking speed and peak oxygen consumption (VO2 peak) obtained during the 6-min walk test (6 MWT) and an incremental shuttle walking test (ISWT) in a trained older population. Methods: A total of 22 older adults (16 female and 6 male) with a group mean age of 70±5.8 yr (range 58 to 79) completed the 6 MWT and ISWT within a 2 wk period. Heart rate (HR) and VO2 peak were measured during each test with a portable metabolic cart (Cosmed, K4B2). The VO2 peak, the maximum walking speed and the total distance walked measured during both tests (6 MWT and ISWT) were compared. Results: A total of 110 recordings for the VO2 peak were obtained and analyzed. Strong correlations were found for the VO2 peak and the walking speed (r=0.91 and r=0.89, respectively, for 6 MWT and ISWT). VO2 peak values obtained with the ISWT were significantly greater (P<0.05) than with the 6 MWT (21.6 ± 5.3 vs 18.9 ml/kgmin ± 4.5, respectively). There was no difference between sexes. In addition, the maximum heart rate as predicted from age during the ISWT was reached by all participants while it was not during the 6 MWT. Conclusion: Thus, the ISWT appears to a better tool to assess the maximal aerobic functional capacity in older healthy adul...
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