This is at Axis jiu-jitsu in Fukuoka. On some of the weekdays we do an abdominal workout with about 5 different exercises and on this day it totaled about 500 repetitions.
The larger the class the more sit ups we do.
It’s a really awesome core workout.
I think my stomach actually got a little more cut from this, the intermittent fasting I do, and the exercise I sometimes do when I am fasting: jiu-jitsu, riding my bike 12km a day, working out, etc.