Eli5: How can you get more ill if you exercise vigorously with an underlying cold or fever?
In: 16
Energy that is being used for excercise could be used to fight the illness. Just because your blood is pumping faster doesnt mean more energy is being directed to the places needed.
When you are ill your body contains a high amount of disease-causing bugs. When you exercise you are making blood flow at a higher rate. This means the bugs end up in places where they normally wouldn’t be. This is especially a problem with viral diseases. If you exercise the virus will likely end up in your heart. A viral infection in your heart causes it to swell up, which causes all kinds of problems.
EDIT: Wow damn. It feels like I insulted Ghandi himself rn.
The less your body has to do at once the better it is at it
It can’t focus the entire nervous system on fighting infection if it also has to recover from physical exertion, and while it’s distracted doing that, the infection can get worse
Your body is really efficient, sometimes too efficient. It will prioritize it’s energy flow for the most immediate task (in this case, the exercise), and steal it from the less important needs (like fighting infections, etc). The body can only convert energy so fast, so there is a limited supply of “free” energy to be used at any given point. Given enough time, the body adjusts to it’s energy needs so that it’s almost at equilibrium with how much energy is being released vs stored. Having an infection or cold is a drastic change to the energy requirement your body has and so it doesn’t have time to adapt and will actively steal energy from other processes to fight that ailment. This is generally why you feel tired and terrible when you are sick as your body tries to conserve energy in order to use it to fight your cold.
Think of it like this: Running from predators (immediate short term need) > Fighting illness (secondary long term need) > Repairing damage (Tertiary longer term need).
Your body will either focus on repairing damage, or strengthening the immune system.
If the body only has two hands like us.
You’re building a table and a chair. It’s easier to use both hands on the table. Then one on the chair and one on the table.
When you exercise, many of your body’s systems assume you must be running for your life, either to catch prey or to escape becoming prey.
It’s a red alert, all-hands-on-deck situation. Who cares if you will get sicker–there could be a bear about to eat you!
So almost all your energy goes to helping you outrun that bear or gazelle or whatever, leaving your immune system starved for energy.
We cannot consciously direct the allocation of energy or immune response. All we can do is rest, and give our body no other competing priorities except to fight illness.
Exercise is a stressor on your body. When you are healthy, the stress is actually advantageous. When you are getting sick, the stress of exercise weakens the immune system and makes your body less able to fight the illness
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