Picture this: It’s a hot summer day, you’ve been at sports practice all afternoon and you know your coach always has the team do conditioning at the end of practice. You and your teammates line up and start to sprint. The finish line is in sight, you are almost there! Finally, you cross the line and get to catch your breath before the next sprint. As you start to bend over and place your hands on your knees, your coach reminds everyone to stand up tall with your hands behind your head. Now you’re confused. Is an upright position better for your recovery or are you better off with your hands on your knees?

Your lungs contain nerves called pulmonary stretch receptors that can tell whether or not your lungs are filled with a lot of air. The nerves first send a signal to a part of your brain, then back down to your heart. It tells the heart whether it should beat faster or slower, depending on how full your lungs are. This is known as respiratory sinus arrhythmia (RSA) and it shows the connection between different body systems: respiratory (your lungs), nervous (your brain) and cardiovascular (your heart).

So, which position—hands over the head or hands on the knees—do you think will cause the most filling with air and stretching of your lungs?

If you said hands over the head, you got it right! Putting your hands over your head will cause more lung filling and stretching than bending over. You might wonder why this is. Try it out for yourself. When you’re standing up straight, your ribs—and your lungs—are expanded. When you’re bent over, your rib cage is less expanded and therefore your lungs aren’t either.

Even though it sounds counterintuitive, you don’t want your lungs to be full when you’re recovering from exerting so much energy. Raising your hands over your head tells your heart to beat faster, while in the bent over position, your brain tells your heart to slow down. And after a hard workout, when your heart is racing and beating out of your chest, you want to slow down your heart rate rather than increase it.

So, in this case, it looks like your coach may need a physiology lesson. Bending over with your hands on your knees will help bring down your elevated heart rate. This is one situation where you don’t want to stand tall.