A couple of days ago I learned that the Marine Corp was changing from crunches to planks as the abdominal portion of their Physical Fitness Test. I didn’t learn the minimum time, but was told that 4 minutes yielded max points on the test.
So I tried a plank, and got to 1 minute, by which time I was quivering jelly, with the quivering starting at about 20 seconds. It was hard.
The USMC had seen back and other injuries from doing so many crunches. So I support this. Crunches are tough on your back.
I’m going to add planks to the squats, child pose, and other stretches I do after my 25-30 minute 90c sauna routine. Let the sweat drip!
Here is an article on how to make Planks even tougher. I’m gonna start with normal planks and then move to RKC planks (the first described here).