Have you ever heard of a plank? We bet you have! It is one of the most effective exercises that makes all of the core muscles work. What is more a plank helps to make your shoulders fit and strong. There is a plank challenge that we dare you to take. Are you ready?
The challenge itself lasts 28 days. Even though it might seem quite a long time you will have a break every 5 days. During your workout days you need to increase the amount of time spent in the plank. So, let
