Sit-Ups, Crunches, Planks, Knee-Ups: The Evolution of Core Fitness Testing

Core strength testing has come a long way from the straight-legged, twisting sit-ups used before World War II.

Here's What A Good Core Workout Really Looks Like, thePTDC

Planks or Crunches: Which is Better?

Sit-Ups, Crunches, Planks, Knee-Ups: The Evolution of Core Fitness

Sit-Ups Benefits: Exercises, Variations, and More

4 Ways to Do Sit Ups - wikiHow

Exercising with Diastasis Recti - Which Ab Exercises Are Safe?

11 Core Exercises for People Who Hate Crunches, Sit-Ups and Planks

Hover Exercise vs Plank vs Crunch - Ab Workouts

Forget sit-ups — these 6 exercises will help you sculpt your abs

The Truth about Whether You Should Crunch or Plank Your Way to a

How to Do a Sit Up Correctly, Abs and Core Exercises