Today's is a Twofer.
Part 1: 4 mins of Tabata
Choose the toughest plank that you have done so far and do it in 20 sec intervals with 10 sec rest x 8 rounds. There are so many free tiners available to help you with this. My fav free app is Gymboss
A regular stopwatch will do the job too. Rest for all the 20s and 50s. Pank until 20 and 50,
1:00-1:20 Plank..... For 4 minutes.
Part 2: 7 mins of forearm Plank hold: *for a total time of 7. Take as many breaks as you need in irder to get 7 quality mins of a plank in. Try it all in one attempt or do a min each hour ... Its up to you.
Quality is the goal.