Mountain climbers’ form is starting in a plank or push up position, and drawing your knee to your chest, then, jump back and bring the other knee; think of it like running in place while in a push-up form. Mountain climbers can be done as reps and sets or in a set amount of time. If you’re just starting off, 15-20 mountain climbers is a good rep amount to begin with (comes out to 10 on each side). You can steadily increase this to 50, which would be 25 on each side. You can also consider doing 15 to 30 seconds to begin, increasing this to 60-90 seconds as you become more familiar with the workout.