Bear crawls work your core, shoulders, and quads and are similar to the mountain climbers mentioned above.
Start on the floor on your hands and knees, and lift yourself up on your toes so that your knees are no longer touching the floor. Your knees should be hovering at a 90-degree angle at this point. Next, move your left hand and your right foot forward and then switch to your right hand and left foot.
A common mistake is lifting yourself off the ground during the movements. The idea is to stay low to the ground.
This exercise is suitable for beginners. However, if you have issues with your wrists, one option is to ball your hands into fists.