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The effect of exercise intensity on post-exercise lung diffusion in highly trained athletes Warren, Robert Scott


The purpose of this study was to determine the effect of exercise intensity on the postexercise reduction of the diffusion capacity of carbon monoxide in the lung (DLco) and whether these declines were related to reductions in arterial oxyhemoglobin saturation (%Sa0₂) during exercise. Ten highly trained ( V0₂max = 66.8 ml-kg⁻¹-min⁻¹) males were recruited. Subjects performed a maximal cycling test to determine V0₂max and then returned on three separate occasions to perform ten minutes of submaximal cycling at 90%, 60%, and 30% of V0₂max . During each exercise session, expired gases, HR, and % S a 0 2 were recorded every fifteen seconds. DLco was measured prior to exercise (baseline) and one-hour following each of the exercise sessions. DLco was partitioned into its components of diffusion capacity of the alveolar membrane (DM) and pulmonary capillary blood volume (Vc) by measuring it at two concentrations of inspired 0₂ . DLco significantly declined from baseline following each of the submaximal exercise sessions. The reductions following the 60% and 30%> exercise sessions were similar but greater than the decline that occurred following the 90% exercise test. Reductions in post-exercise DLco were accompanied by declines in DM that reached statistical significance following the 90% and 60% tests, but not after the 30% submaximal exercise session. The decline in post-exercise Vc was also greatest following the 90% submaximal session and similar for each of the 60% and 30% tests. However, Vc reductions did not reach statistical significance following any of the exercise intensities (p=0.10). % S a 0 2 during 90% submaximal exercise declined significantly greater than both the 60% and 30% exercise tests, and all were decreased below baseline. No correlation was found between the post-exercise reductions in DLco, DM, or Vc, and % S a 0 2 at any of the exercise intensities. In summary, the results suggest that measurement of post-exercise DLco at different intensities of exercise does not reflect oxygen saturation levels during each test. Furthermore, the validity of using post-exercise measurements of DLco to indirectly implicate pulmonary edema as a mechanism of EIH is questionable.

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