Ten well trained cyclists were studied and compared with 12 untrained subjects from a previous study to determine the effects of a high intensity, constant workload bout of cycling on maximum expiratory pressure (Pe_max). Subjects completed a graded exercise test on a Monark cycle ergometer while expired gases were collected to determine maximal oxygen consumption (VO_2max). Subjects then returned on a second day when measurements of each subject's Pe_max, were made prior to riding at the workload corresponding to 90% of their VO_2max until exhaustion. Measurements of expiratory pressure (Pe) were then made immediately post exercise (Pe_IPE), one minute post exercise (Pe_1MIN), three minutes post exercise (Pe_3MIN), and five minutes post exercise (Pe_5MIN). Trained cyclists had a significantly higher Pe_max (x = 116.43 ± 7.76 mmHg) than did untrained subjects (x = 65.75 ± 7.09 mmHg). Also trained cyclists generated a higher absolute Pe throughout recovery than did the untrained subjects. Although expiratory pressure decreased after exercise in both groups, the relative change in Pe over the recovery period, expressed as a percentage of Pe_max, was not different between trained and untrained. Pe_IPE was decreased to 81.87% ± 3.12 of Pe_maxin trained subjects and 82.35% ± 2.85 in untrained subjects (p < .05), recovering somewhat at 1 minute to 89.19% ± 3.59 of Pema, in trained and to 87.74% ± 3.27 in untrained (p < .05) but did not recover to resting levels in either group. Pe_3MIN and Pe_5MIN remained at the same level as Pe_1MIN in both groups. Therefore, a high intensity, short term exercise bout caused expiratory pressure to be decreased in both trained and untrained subjects. / Master of Science