What is the most important muscle you use when your running?

Question

And how can you increase this muscle easily?

Answer 1

I don't think any one muscle is important. You need all of them to be a good runner. Calves for speed, quads/thighs for power and endurance. Even your arms! Because if you can't carry your arms right and keep them pumping strong then your whole upper body starts to collapse and makes your form terrible. So you need to condition yourself to where you can have all these muscle groups working together. Hope this helps!

Answer 2

The most important muscle is the HEART. I don't think this is what you meant, but it is really the most important one. The one you wanted is your glutes (thigh) and the calf muscles.  

Walking and running and muscles strengthing exercises will increase these muscles.

Answer 3

i would say your calves. The easiest way is to do toe ups (it's when you lift your heal up and down using your toe) This exercise is very good, and try to put extra weight on you you for better results xD.

Answer 4

your cardiovascular muscle or in simpler terms, your heart.

you can increase heart performance by increasing heart rate during exercise or any physical activity

Answer 5

i'd say run a few miles and take a warmdown lap