During a lesson on heart rate, I was demonstrating to one of my kindergarten classes how to check their pulse. We learned which fingers to use and that you should never use your thumb. I asked the class if anyone knew why it is not a good practice to use your thumb to check your pulse? One student was waving his hand and jumping up and down with excitement. I Know, I know!! Why do you not use your thumb Jacob? "Because you need your thumb for sucking."