SHOULD I REALLY EXERCISE IF I CAN'T BREATHE THROUGH MY NOSE?
Well, the answer is no. Exercise is not a cure for the common cold. Contrary to popular belief there's no such thing as sweating out a cold. You may feel better after a workout, but it's no different than feeling better after any workout. The relief you feel from your cold is solely due to your endorphins kicking in. Therefore, exercising when you're should not be treated as a cure for your cold. Still, working out when you're sick is okay to do, provided you're only suffering from certain symptoms. For example, common head cold symptoms like stuffy nose, runny nose, congestion, or a sore throat are all okay to work out through. However, if you're dealing with a stomach bug like the flu, fever, or chest congestion, it's not a good idea to overexert yourself. Here's a quick guide to when it's okay to workout when you're sick, and when you should be more cautious.
Feel free to workout if you're experiencing...
Stuffy Nose
Runny Nose
Nasal Congestion
Sore Throat
Skip your workout if you're experiencing...
Fever
Chest Congestion
Nausea
Vomiting
Diarrhea
Excess Fatigue
As you can see, the skip your workout column includes mostly symptoms you'll be experiencing below the neck. Any of these symptoms can result in dizziness or dehydration, which can either be dangerous for the gym or exacerbate your illness. Rather than overexerting yourself, stay home, skip your workouts and focus on staying hydrated. Drink plenty of water and perhaps supplement your diet with protein shakes if you can stomach them. Sleep a lot and just allow your body to heal itself.
On the flip side, most above-the-neck symptoms are okay to work through, with limitations. When you're not feeling 100% make sure to reduce your workout intensity to about 50% of your normal capabilities. Cut your weight and reps in half, as well as your cardio duration. The average person's cold lasts 7-10 days, so I understand not wanting to take that entire time off. However, take it just a bit more easy on yourself during this time. Also, adhere to gym etiquette for goodness sake. If you're not feeling well, skip the gym and work out at home. The gym is a breeding ground for germs and viruses so try not to contribute by spreading your sickness.
Once you're feeling better avoid leaping back into your normal routine because your immune system may still be slightly weak. Instead, do a progressive overload for the first 3 or 4 days until you're back to 100% of your normal intensity. You may notice a slight decrease in your endurance or strength once you return, but not to fret. It will only take you a few days to get back to your normal intensity.