Getting your annual flu shot is important not only for your own health but those around you. Does that mean you have to skip your workouts for a few days afterward as your body adjusts? Actually, the opposite is true: Exercising both before and after your shot can increase the effectiveness of the vaccine.
"Not only is it completely safe to exercise, but it's recommended," says Joshua Scott, MD, primary care sports medicine physician at Cedars-Sinai Kerlan-Jobe Institute in Los Angeles. "The shot itself is only about 70-percent effective, but you can increase that number by working out right after you get the vaccine."
How Exercise Can Help Boosts Flu Shot Effectiveness
One of the most notable studies on flu vaccines and exercising in from a November 2004 study from the journal Vaccine, where researchers looked at adults over age 65, a group that usually has reduced response to flu vaccines. They found that those who exercised consistently showed a much higher level of antibodies after getting the flu shot than those with lower levels of activity.
But you don't have to be a regular exerciser to see similar benefits. In research from February 2007 published in Brain, Behavior and Immunity, participants lifted weights for 20 minutes about six hours before receiving a flu shot and were compared to a control group that received a shot at the same time but didn't exercise. Researchers checked participants a month later and found that those in the weights group had higher antibody levels.
In terms of exercising after your flu shot, that strategy can also increase antibody levels, Dr. Scott says, and also be a big-time immunity tonic, thanks to a range of benefits — better sleep, lower stress, more efficient white blood cell circulation, less bacteria in the lungs and other effects — which can all make you a cold- and flu-fighting machine throughout the winter months.
"Your body loves exercise, because it bolsters the immune system and helps you function better in nearly every way," he says. Plus, research suggests it doesn't even take much activity to see that ripple effect.
For example, a January 2019 study from Applied Physiology, Nutrition and Metabolism found that just a few intervals of rapid stair climbing had a positive effect on cardiorespiratory fitness. Another April 2013 study from Human Vaccines and Immunotherapeutics, on exercise and vaccines specifically, noted that even a single bout of exercise could bolstered the immune system.
3 Tips for Exercising After Getting the Flu Shot
Even though a workout can be a major immunity booster, there are some considerations to keep in mind, particularly when it comes to side effects. Here are some recommendations from exercise physiologist Rondel King, CSCS, at the Sports Performance Center at NYU Langone Health, about the safest ways to get your sweat on after you've had the flu shot or nasal spray vaccine:
1. Stay Hydrated: When people work out after a flu shot and feel slightly dizzy or lightheaded, it's usually because they're at least a little dehydrated, King says. That can be very challenging for your body as it's trying to fight off those influenza microbes. So hydrate, hydrate, hydrate!
2. Watch the Intensity: From flu shot to bootcamp class? While it's not the worst idea, King recommends a more moderate workout, like strength training or steady-state cardio, mainly because of hydration. "If you're at maximum intensity, it's easier to get dehydrated," he says. "Also, you don't want to create too much fatigue, because keep in mind that your immune system is in overdrive, and fatigue might be counterproductive for that."
3. Make It Leg Day. Doing an arm workout won't do anything to minimize the effectiveness of the shot or to harm your muscle in some way, but many people do experience soreness in the area where the shot is given. Because of that, King suggests focusing on lower-body exercises so the shot-related soreness isn't exacerbated.
When should you not exercise? More serious side effects like spiking a fever are very rare, says Dr. Scott. But if that does happen to you, he suggests foregoing the exercise and checking in with your doctor instead. That’s also a good idea if your side effects — such as fatigue, achiness, or lightheadedness — are lingering past the 48-hour mark and/or are worsening.
In general, though, any side effects tend to subside within a day, and exercise is likely to speed them along even faster, Scott says. "Consider exercise to be a flu-shoot booster and just a good strategy for lowering your risk of colds and flu altogether," he says.
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- Centers for Disease Control and Prevention: Key Facts About Seasonal Flu Vaccine
- Vaccine: Moderate exercise improves antibody response to influenza immunization in older adults.
- Brain, Behavior and Immunity: Eccentric exercise as an adjuvant to influenza vaccination in humans.
- MedlinePlus: Exercise and immunity
- Applied Physiology, Nutrition and Metabolism: Do stair climbing exercise “snacks” improve cardiorespiratory fitness?
- Human Vaccines and Immunotherapeutics: Effects of exercise on vaccine-induced immune responses