I have just started hit, I'm doing stair sprints! Been doing it 2 weeks it'd going awesone, stomach is starting to tighten & firm up.
30 sec sprints. 30 sec walk. I'm currently up to 20min.
Started of and in 10mins I was ****ed, but yesterday went for 20-25 mins.
Every few sets il actually jump with both feet to every second step as quick as I can, can feel it also working on my lower abs.