Exercise and immunity: moderate helps, extreme hurts
September 29, 2026 · 21 min read
Roger Seheult's J-curve and Huberman's cold, flu and immune episodes agree that regular moderate exercise strengthens immunity while very intense bouts can temporarily weaken it. It helps active people train smart during cold and flu season.
The rules, numbers and steps worth keeping in front of you.
- The J-curve, per Dr. Roger Seheult: no exercise is normal risk, moderate exercise lowers it, more and harder exercise raises it again.
- McMaster moderate dose: heart rate about 140 for about 20 minutes, three times a week; depression, anxiety and inflammatory markers fell.
- McMaster high-intensity dose, around 180: less benefit for depression, no relief from stress, higher interferon.
- Andrew Huberman: 60 minutes or less at a hard but not all-out effort primes innate immunity for many hours, perhaps up to 24.
- Huberman's session rules: 5 to 10 minute warm-up, 50 to 60 minutes of work, caution beyond 75 minutes.
- Huberman: never two hard sessions in one day, and take one day a week off.
- Huberman's baseline: about 150 to 180 minutes of zone 2 cardio per week.
- Huberman's three patterns before his colds: two hard workouts in a day, hard training plus cold exposure while traveling, nights of two hours of sleep or less.
- After a bad night, cut intensity and duration by 25 to 50%; never trade sleep for exercise.
- After fasted sessions beyond 60 to 75 minutes, eat complex carbohydrates and fruit within about an hour.
- Malaise, unexplained fatigue or a throat tickle: rest. With symptoms, do not exercise at all.
- Marathon training and Olympic-level blocks leave people more vulnerable.
- Talk with a doctor first if you are immune-compromised, pregnant, have a heart or chronic condition, or are returning after illness.
This is the short form. The full insight has every expert's reasoning, their own words and the sources.