 Each subject will attend 4 visits to the laboratory. Visit 1 screening visit will involve a record of medical history, medications used, anthropometrics measurements, questionnaires, breathing tests, an incremental cycle exercise test and a constant-workload cycle exercise test. Visit 2 will involve breathing tests and a constant-workload cycle exercise test. Visits 3 and 4 will involve breathing tests and a constant-workload cycle exercise test after subjects have been randomized to either placebo or Atrovent. These visits will be done on separate days and subjects will receive the two above treatments in random order. 