The best replacement for crunches is sit ups.

The best alternatives to crunches are rated as following:
★★★★★  sit ups
★★★  planks
★★  leg lifts
★★  leg raises
★★  reverse crunches
★  sit ups difference
★  curl ups
★  plank
★  situps
  sit ups better
  bicycle crunches
  ab machine
  hanging leg raises
  pilates
  push ups
  ab wheel
  situp
  sit up
  situps better
  curls
  sit-ups
  full sit ups
  ab machines

Your alternative for crunches is not listed? Suggest!
Speaking about crunches, one probably shouldn't forget about weights.

Other search terms related to crunches and their ratings are:
★★★★★ weights
belly fat
crunches
neck strain
sit ups
You have in mind a companion for crunches and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of crunches in all years. Click on graph for more.
crunches
sit ups
planks