20 Intense mountain climber variations for demolishing the abs and developing a strong supporting core!
Mountain climber is a support position similar to the regular plank. The difference is that it's a dynamic hold because you are alternately bringing your knees up.
Once you have built high levels of support strength (this is covered in Abs 20XX), mountain climber becomes a fun alternative to train the abs.
In the mountain climber, it's the plank hold that trains the abs - when you bring the knees up, you are mostly training your hip flexors. However, when you balance yourself on one leg at the time, your body needs to focus on anti-rotation which requires more juice from your stabilizing abs and obliques.
If you feel the exercise in your lower back, then your abdominals aren't properly engaged. You need to suck the stomach in and hold the position with your abdominals only (if you want to train the abs).
The possibilities are nearly endless and you can make the mountain climber a serious strengthening drill by changing the angles of your trunk, increasing speed, alternating your hand position (the higher the arms, the harder it will be) and leaning forward (planche style).
If you get bored with the regular plank, then mountain climbers can be the killer exercise to finish your workout and burn some calories.
PS. We recently released Abs 20XX. It's a comprehensive 95 page abs & diet guide covering everything you need to train the core to its full potential (almost no one does this) and how to eat to get lean and get the six pack (intuitive eating).
The guide is affordable and full of practical advice you can put into good use. We put our heart and soul to make it the best guide possible to actually produce you results.
Train hard, stay safe.