Is it okay to exercise with a cold?

Short answer

With a head cold and moderate intensity, yes. In an experiment giving 50 people a cold virus, 40 minutes of moderate exercise every other day did not worsen symptoms. Feeling feverish disrupted running form, and in mice whose virus reached the heart, exercise increased heart damage.

Is it okay to exercise with a cold?
"Sweat it out" vs "Exercise makes it worse": which is right?
People disagree on whether to rest or sweat it out when a cold comes on. We checked using experiments that gave people a cold virus on purpose, and real-world records.
They gave people a cold virus and had them exercise
Symptoms did not get worse in the exercise group
After 50 people were given a common cold virus, 34 exercised at moderate intensity for 40 minutes every other day for 10 days, and 16 did not exercise. Symptom scores and the weight of used tissues showed no difference between the groups. Symptoms right before and right after exercise did not change either.
What about performance at the worst point?
Lung function and maximal running capacity held steady
45 people were given a common cold virus and retested on the day symptoms peaked. Resting lung function, the body's response to moderate running, and maximal capacity when running to exhaustion all showed no difference from before the cold.
But feeling feverish changed things
Running form was more disrupted
18 people with a cold and 20 without ran on a treadmill twice, 3 weeks apart. With a cold, stride length, step rate and ankle angle changed more, and those who felt feverish had bigger changes in stride length and step rate. No one had a measured fever.
It is different when a virus reaches the heart
In mice, exercise increased heart damage
When mice given a virus that inflames the heart were made to swim 60 minutes daily for 9 days, deaths rose from 0~10% to 20~40% and heart muscle damage grew. In a 2024 experiment, mice that kept running at moderate intensity lost less weight, but 82.4% developed heart scarring, versus 56.3% of mice that rested.
How many days do people actually miss?
80% did not miss more than a day
In an analysis pooling 54 studies and records of respiratory illness in 31,065 people, missing more than a day of training or competition happened in 20.4% of cases. The other roughly 80% did not miss more than a day. Symptoms lasted 7.1 days on average.
Summary: with a head cold, up to moderate intensity was fine
If you feel feverish, resting is the move
In cold virus experiments, 40 minutes of moderate exercise every other day did not worsen symptoms, and performance held steady. Feeling feverish disrupted running form, and in mice whose infection reached the heart, exercise increased heart damage. If you feel feverish, resting works; with only nose symptoms, moderate intensity works.