Working Out While Sick with a Cold
A general rule of thumb to determine if it's okay to exercise or not is to check if your symptoms are above neck or below it. If you have runny nose, sore throat, a light workout session at gym will probably do you some good. However, make sure your cold symptoms are mild only. Sniffles or congested nasal passage can open up during a brisk walk at a park or a light cardiovascular exercise at gym. However, following this rule blindly is not advisable. You need to assess your symptoms and decide for yourself, whether your body can handle a workout session or not. When in doubt, it is best to stay at home and rest rather than sweat yourself at gym.
Working Out While Sick with Fever, Stomach Problems, Body Ache
Needless to say, all of the above conditions warrant bed rest. When you are suffering from high fever, your heart is already beating faster to bring down the elevated body temperature. In that case, if you subject it to a workout, you will do more harm than any good to your own body. Similarly, stomach ache, diarrhea etc. should be dealt with patience and lots of rest. Working out while your body aches or you have chills is also a bad idea as your body may break down from exhaustion. The 'neck rule' also applies in this case, as all the symptoms mentioned above occur below the neck.
Why Working Out While Sick May Not Be a Good Idea
When you workout, your body goes on to build muscle, when you rest it. However, when you are sick, your immune system is compromised. In this condition, body should get enough rest to strengthen its immune response. Muscle building can take a back seat for time being. However, when you exert your sick body, your immune system does not get time to recover itself, as a result you might prolong your illness.
It has been observed that people who strictly follow a workout regimen need to take a break from training after 8 to 12 weeks. If this break is not taken, they feel under the weather due to some reason and fall sick. However, taking a break from working out for 4 to 7 days ensures that you come back to the gym stronger and healthier than before. During this break, you need not train your body, but you can keep it active by indulging in a sport of your choice. Thus, 8 to 12 weeks of training followed by a week of rest is the best way to preserve your good health. Also read how often should i work out to answer your workout related queries.
Another reason why working out while sick is not recommended is because when you are sick you are very much likely to transmit your infection to other people. If you go to a public gym, people can easily get infected from touching the machines that you unknowingly contaminated. In the end, one should assess their health and decide what is best for their own body.