i can currently do 1000 double crunches without stopping... consequently its reached the stage where that core exercise does nothing for my abs im wondering if i should
a. do the double crunches with weight (ankle weights and holding dungbells) or
b. do another core exercise harder then the double crunch.

im looking for peeoples opionions on this, if you choose b. can u please reccomend an exrcise... prefferably harder then the double crunch but working the same ab muscles as oi already do a variety to work my whole abdominal region.