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

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

Exercising with Diastasis Recti - Which Ab Exercises Are Safe?

Fitness

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

What are the differences between squats, lunges, and push-ups and crunches/ sit-ups and leg raises/planks? - Quora

Come plank! It engages more muscles than crunches or sit ups. Plus it burns more calories!!

Strengthen Your Core Properly With These 3 Exercises

The Major Differences Between Sit-Ups and Crunches

What Happens to your Body When You Do 100 Sit Ups Every Day for 30 Days?

How to Do a Sit-Up with Proper Form - Steel Supplements

5 Amazing Six Pack Abs Exercises that are Superior to Boring Sit Ups

The Major Differences Between Sit-Ups and Crunches

Sit-up - Wikipedia

That powerful connection between exercise and teens' brain development

Fitness

Beginner Ab Workout Without Crunches - Postpartum Ab Exercises - Diastasis Recti Safe Workout