Timed sets for grip?

Training Bodybuilding
1

In the DeFranco article, it calles for 3 sets of timed sets for grip training. How does one determine the time, for say wrist roller?

2

Or, do you just do it until you can’t anymore and try to do more time next time?

3

I would say that for the wrist roller you wouldn’t do timed sets, just reps counting times “rolled” up/down/whatever. But, for the other grip excersizes you would time how long you would hold the bar/db’s and try to surpass that time the next workout.

4

Or you get a brain and find out what hes actually talking about…wrist rollers…