Judge how well your abdominal muscles are doing by testing them with a backwards sit-up. Start by sitting with your feet flat, legs bent, and fingers behind your ears with your elbows out. Try to lower yourself down slowly; any less than 5 seconds indicates that you need to focus more on your abdominal routine. The best way to do that is by working on your abs first in your exercise routine.
You should avoid trying to exercise when you are ill. If all of your symptoms are above the neck, you may still exercise if you want. If you are sick and working out, your body will be trying to heal itself. It will not be focused on building muscle and endurance. If you are sick, it is best to stop exercising until you are better.