Peter Berglund via Canva.com

After an intense running session or competition, you’re not just left with tired legs; your immune system also takes a hit. This is where the so-called «Open Window» effect comes into play.

Following particularly demanding sessions such as interval training, a long-distance run, or a race, a brief “window of vulnerability” opens up, known in professional terms as the Open Window. During this phase, your immune system is weakened due to the physical strain and is so busy repairing muscle tissue, clearing out damaged cells, and restoring internal balance that it has reduced capacity to fend off pathogens. In other words, you're more susceptible to infections during this time.

Recent studies show that this phase typically lasts only a few hours, much shorter than previously thought. However, in this narrow window, viruses and bacteria can more easily enter the body, especially if you’re standing around sweaty in the cold or immediately enter crowded places after your workout.

Even though the immune system is under special strain during the Open Window, this doesn’t mean you’re guaranteed to get sick. But it’s worth taking extra care during this sensitive time.

These measures help:

• Change quickly: After exercising, immediately switch out of wet clothes and into dry, warm ones.

• Hot shower: Stabilize your body temperature, thoroughly dry your hair, and wear a hat if necessary.

• Rehydrate: Drink plenty of fluids soon after to quickly compensate for fluid loss.

• Eat early: In the first 30 minutes post-workout, your body absorbs nutrients best. A combination of carbohydrates and protein, either as a meal or a recovery shake, supports optimal recovery.

• Prioritize sleep: Plenty of sleep is essential for recovery and quickly restoring immune function.

• Avoid alcohol: Alcohol hinders recovery and should be avoided after intense sessions.

• Steer clear of crowds: During the Open Window, avoid buses, trains, shopping centers, clubs, or other crowded areas.

• Stick to rest days: Recovery is part of training. Make sure to take sufficient breaks, especially after tough workouts. Even elite athletes rarely do more than two to three intense sessions per week.

Exercise remains the best medicine

Despite the Open Window effect, the takeaway is clear. Regular exercise has been proven to strengthen the immune system. If you maintain a healthy balance between effort and recovery, you’re doing everything right by training not only efficiently but also in a way that supports long-term health.