Abs and a forearm supination excercise

Today I had a pretty relaxed day and cooked a few meals in advance for tomorrow. My legs are super sore after yesterdays high rep leg but besides that I'm not feeling too bad. This afternoon I had a brisk 30 min walk after some ab and forearm work. For abs I did two supersets of reverse crunches and vertical leg crunches on the bench (30 reps), and for forearms I did 3 sets of a new forearm supination exercise I came across.

Here's a video that shows the exercise (I used a half loaded dumbbell instead):