If a run-of-the-mill cold or cough forces you to skip a few workouts, it shouldn’t take long to get back up to speed. But if the flu, bronchitis, pneumonia, or another nasty illness sidelines you for weeks or even a month, returning to regular exercise can be a beast. Your cardiorespiratory fitness will have dwindled, and your whole body will be beaten down from battling the infection. And if you jump back into your routine, you may be doing more harm than good.
Overtaxing your body after a prolonged illness is risky for a few reasons. First, your once-toned muscles have been idle for weeks and, as you’ve probably noticed, have shrunk. Like it or not, you’re now in a similar boat as a couch potato who suddenly decides to start exercising, says Dr. Donald Hensrud, director of the Mayo Clinic Healthy Living Program in Rochester, Minnesota. Your underused muscles will get sore a lot quicker than you think, and if you work them too hard, you’ll risk a strain, sprain, or tear.
Additionally, your immune system likely isn’t back to full strength. Although routine exercise helps boost immunity, if you’ve been inactive for a long time, or if you push your body way past its limits, immunity can tank for the next 24 hours or so, says Dr. Matt Gammons, of the American Medical Society for Sports Medicine. “After you’ve been really sick for a long time, particularly following bronchitis or pneumonia, it’s common to get a post-infection cough or other inflammatory issues,” he says. “You may have been feeling better but then find yourself hacking or wheezing.”
In other words, it’ll take longer than you’d like, and you just have to accept that. “Whether it takes two, four, or even six weeks to get back to full speed, that’s still not a lot of time in the big picture,” Hensrud says. “It’s more important to ease back in the right way so that you’ll stick with it.”
Walk before you run (literally). If you’re used to running five miles and doing strength work most days, a casual stroll might not sound like much of a workout. But after weeks of inactivity, you’ll be surprised by how much walking wears you down. “You might actually still be fighting off this sickness, so starting out with a walk is a good way to gauge whether you’re ready to resume exercising,” Hensrud says. “It’ll allow your muscles to move without taxing them too much.”