Every bootcamp instructor and personal trainer in the world uses mountain climbers as a method of conditioning. Usually the clients butcher the technique with the trainer standing idly by, if for no other reason than they don't know why they are prescribing this exercise, or the immense benefits that can be had from the use of proper technique.
When done properly, the mountain climber will effectively develop the athletes ability to dissociate their legs by concurrently achieving full hip extension with one leg and full hip flexion with the other. This is critical for optimization of sport movements such as sprinting and jumping off of one leg (as seen in soccer, football, basketball etc), along with lifes activities such as hiking and climbing stairs.
Mountain climbers done with proper technique also require the athlete to achieve dorsi flexion at the ankle of the flexed leg. The ability to instinctively dorsi flex the ankle during the recovery portion of a sprinting stride will vastly decrease the risk for hamstring injuries. With this in mind, can the mountain climber not also be a great evaluation tool for athletes?
During mountain climbers, the athlete must powerfully explode off the ground with the extended leg, while also explosively pulling the flexed knee towards the chest. Developing a powerful push off in the mountain climber will enhance the athletes power generation during a sprinting stride.
Lastly, when done properly, mountain climbers will teach trunk stability from the hips all the way up to the shoulder girdle. And for those training for the summer season, it is also a great exercise for safely developing your abdominals without putting your spine and posture at risk via countless crunches and sit-ups.
-Keep the lats tight and the thoracic spine flat
-Brace your stomach as if someone was going to punch you (think about having 'Batman' abs)
-Explosively drive your extended leg into the ground, and powerfully pull your knee to your chest
-Dorsi flex at the ankle of the flexed leg
-Keep the hips as stable as possible. Do not allow your hips to raise above the level of your shoulders