Ouch! I just did this work out and boy can I feel it! I feel it a lot in my abs crunches does that to ya!) and then also in my arms from the pushups and planks! I skipped the second bridge because I didn't find it very worthwhile (didn't really fee.
This is a rather decent interval training treadmill plan. Its probably a bit intimidating for those new to running; the important thing is short spurts of sprints spaced between long runs at a somewhat uncomfortable pace.