Weighted Planks

[devilsrule61287]

For my ab routine, I always do 9 minutes of planking (1 min regular, 1 min left side, 1 min right side, rest and repeat cycle twice). Whenever I'm able to do all 9 minutes without failure, I add some weight and keep working at that weight until I am once again able to complete all 9 minutes. My question is whether it is better to do minute-long planks with lighter weight, or make the planks 30 seconds each, which would allow me to apply more weight.

Ex. I currently put 10-15 lbs on my back/hips and get through all 9 min, but if I did 30 sec. planks, I could probably put on a 25 lb plate. Which is better?

[devilsrule61287]

Or perhaps it is better to alternate between workouts? (i.e. one workout, do min-long planks with lighter weights, and the next do 30-sec planks with heavier weight)

[devilsrule61287]

Bump. Any advice from those who do planks?