Okay, let me explain to you what is the bainbridge reflex.
When you run and play outside, your heart beats faster and you start breathing harder. Your heart and lungs have to work together to pump more blood and oxygen to your body.
The bainbridge reflex is a special way that your body helps your heart when you are exercising. Your heart has special sensors that can tell how much blood is in your body.
When you start running and your heart beats faster, your heart sends a signal to your brain. This signal tells your brain that your heart needs more blood.
Your brain then sends a signal to your kidneys. Your kidneys are organs in your body that filter your blood and make pee.
The signal from your brain tells your kidneys to make more pee. This helps to get rid of some of the extra fluid in your body so that your heart has enough blood to keep pumping.
So basically, the bainbridge reflex is like a special phone call from your heart to your brain and kidneys. It helps your body make sure that your heart has enough blood to keep pumping when you are exercising.