It is usually safe for a person with a cold to exercise, according to WebMD. It is important to pay attention to the body's signals to avoid overworking the body and causing more harm than good.
Some cold medicines, such as decongestants, can increase the heart rate, according to WebMD. The combination of exercise and medicine may overwork the heart, leading to shortness of breath and difficulty breathing. If a person has asthma and a cold, it is best to talk to a doctor before exercising as the exercise may lead to an increase in respiratory symptoms. If a person has a fever, the exercise may stress the body even more, causing the person to feel worse and increasing recovery time.