Cardio Exercise You Can Do When You're Sick

Depending on your symptoms, exercising when you have a cold might be the last thing you want to do. But often, doing some gentle exercise will actually make you feel better.

As explained by the Mayo Clinic, regular cardio exercise is acknowledged to boost your immune system and help your body fight off viral illnesses. But what about if you're already sick? The science isn't quite as clear then, with MedlinePlus noting that scientists haven't definitely established exactly how or if exercising when you're already sick helps your immune system.

However, they do note that if you're not feeling well, taking a walk or doing simple exercises might give you a much-needed boost — and there are a few theories on the reasons for that. One is that physical activity might help flush bacteria out of your lungs and airways; another is that exercise-induced changes in antibodies and white blood cells help your body fight off the illness.

Perhaps exercise's role in reducing stress helps bolster your immune system too, or it might be that the rise in body temperature when you work out helps your body fight infection and keep bacteria from growing — much like a deliberately induced fever. That said, despite numerous folk theories about the idea and the aforementioned theory about elevated body temperature during exercise, there's no scientific proof that you can really "sweat out a cold."

Read more: Should You Exercise When You Have the Flu?

There's a well-established body of evidence that exercise can reduce your incidence of illnesses. For example, in a February 2014 analysis published in the Canadian journal CMAJ, researchers noted that although definitive evidence was ultimately lacking, people who did regular cardio exercise self-reported fewer colds.

And in the noteworthy September 2011 issue of the British Journal of Sports Medicine, scientists report on following more than 1,000 adults for 12 weeks during the fall and winter. They found that the subjects who reported doing at least five days of aerobic exercise each week also reported significantly fewer days of upper respiratory tract illnesses, when compared to sedentary individuals who reported exercising once (or less) per week.

If you go all the way back to the November 1998 issue of Medicine and Science in Sports and Exercise, you'll find a small study of 50 individuals. It was conducted with the goal of determining how exercise affected the severity and duration of a rhinovirus-induced upper respiratory illness — also known as the common cold.

All the subjects were inoculated with rhinovirus; some of them exercised while ill while others did not, and all subjects completed a survey about their symptoms. The scientists also collected and weighed used facial tissues as an objective means of measuring symptoms and their severity. The researchers concluded that moderate exercise training, under the specific conditions of the study design, did not alter the severity or duration of the subjects' colds.

Despite the amazing results and insight you get from clinical science, sometimes it's surprising just how little-understood some of your body's essential processes are — and this is one of those cases.

Ultimately, the accepted consensus is that some exercise is almost always helpful in making you feel better or at least taking your mind off "above the neck" symptoms like a cough, even if it's not entirely understood whether or how it might shorten the objective duration and severity of your symptoms.

However, too much exercise can also do you harm — and the definition of "too much" varies depending on many factors, including your level of physical fitness. So, as vague as it might seem, as long as you don't have any conditions that require medical supervision, the best plan when it comes to choosing whether or not to work out when you don't feel well is to let your body be your guide.

Walking, easy cycling and pedaling an elliptical are all examples of light exercise that you can easily modify to be easier — or harder — as your body dictates. Your goal is to find that just right level where doing exercise when you have a cold leaves you feeling stronger and more energized, instead of wrung out. Even if you don't feel like working out while you're sick, light workouts are a good way of re-entering the gym once you start feeling better.

Read more: Cardio Exercises and Sinus Pressure

What about doing resistance training while sick? Again, if you're dealing with a minor ailment like the common cold and feel up to hitting the weight room, let your body be your guide. However, keep in mind that you probably won't be up to lifting at your full intensity.

Depending on your symptoms, you'll almost always want to skip any inverted exercises too — think decline bench presses, decline crunches or sit-ups, exercise ball pikes and the like. If you do yoga, you might want to scale back your practice, avoiding or limiting inversions and other challenging poses. The only thing worse than dealing with unpleasant congestion is trying to do so upside down.

Above all, keep safety in mind. Scale back the resistance loads or challenging calisthenics and consider using a spotter or other safety equipment — such as a squat cage with stoppers to catch the bar, a Smith machine or selectorized strength training equipment — as backup until you feel like your normal self again.

Sometimes you don't fully realize how much a cold or other common illness is affecting you until you're you're stuck on the weight bench with a barbell on your chest, or hacking and coughing unexpectedly in downward dog. When even medical researchers point out that the common cold can be debilitating — potentially reducing your productivity at work and even affecting other activities such as driving — you have full license to take it seriously.

Even if exercising makes you feel better, it has the potential to make others around you feel worse if you head to the gym while still contagious. If you can, work out in ways that minimize exposure to others — for example, going for a walk in the open air, or working out with dumbbells or your own body weight at home.

If you do go to the gym, be considerate of others and practice diligent hand-washing. As the Centers for Disease Control and Prevention point out, regular hand-washing is one of the most important measures you can take to keep from spreading germs to others. It also protects you, because having one type of illness doesn't magically keep you from contracting others.

And finally, if exercise makes you feel worse instead of better, stop and remember that part of letting your body be your guide means going to see a doctor if you're not recovering as you normally would. Most of the time, a case of the cold or flu is exactly that, but on occasion those symptoms may in fact belong to a more serious ailment that your doctor can diagnose and treat.