Take your time recovering from illness before resuming exercise
After recovering from a nasty little bug a few days before the challenging Great Barrier Island Marathon earlier this month, I've noticed a few things and have been trying to make sense of them. Since finishing the run, I have been struggling with a reoccurrence of the illness which seems to have moved deeper into my lungs, despite feeling quite good for a couple of days after the race. It seems clear that our immune systems are compromised for up to 72 hours after what is termed 'excessive exercise', of which running a marathon is a good example. Other studies point to cellular damage after running a marathon, which includes oxidative damage. For example, this study shows that a damage marker persisted for more than 7 days after a marathon. Of course, muscle soreness and tiredness indicates that skeletal muscle damage has also taken place. One study suggests that muscle power and endurance is significantly impaired in calf muscles for up to two weeks after your marathon.
I've tried to take these lessons on board, and took the entire week after the marathon off. I ran a 10km after a week, but that felt too early, as I laboured through it - possibly because I hadn't left enough time after lunch though. I've still not quite recovered yet though, so a gentle 4km treadmill run/walk is all I've done this week. I'm still taking it easy.
More worrying is the potential for myocarditis, which can affect athletes and non-athletes alike. However, athletes and active people are particularly at risk. Myocarditis is a heart inflammation which can occur when an athlete resumes training too soon after a viral infection or cold. The best protection against it is to recover thoroughly after illness before resuming training. That means waiting at least a couple of days after you stop producing yellow or green phlegm. The phlegm means that nasty bugs are still circulating around your body. The worst case scenario of overexerting yourself too early after you've been ill is that an undetected myocarditis can lead to cardiac arrest and death. If you do notice symptoms like a higher resting HR than usual, or night sweats, or more obvious signs like chest pain or shortness of breath, it's probably best to get yourself checked out by a doctor.
The main message is to make sure you rest and recover after you get ill. And don't start exercising vigorously too early.