Whether or not a patient with pleurisy can exercise should be determined based on the individual's specific condition. For mild pleurisy without pleural effusion and severe pain, exercise is permissible. However, if pleural effusion is present, it should be drained or aspirated first, after which exercise can be encouraged. Exercise should be moderate, as it can help absorb the pleural effusion, which is beneficial for the patient. Additionally, if pleurisy causes severe pain, it is best to minimize movement to avoid exacerbating the pain.