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.

Forget sit-ups — 10 best crunches and variations to…

Forget planks — this 15-minute crunches workout sculpts your abs

15-Minute Ab Workout, Abs and Core Exercises

Sit-Ups Benefits: Exercises, Variations, and More

How to Do the Sit-Up for Stronger, More Muscular Abs

Core Training –

The Great Abs Mistake - Crunches And Situps And Still No Abs

Freeletics Exercises: Crunches

Abdominal Muscles: Names, Location, and Function

Fitness

The Major Differences Between Sit-Ups and Crunches

Exercising with Diastasis Recti - Which Ab Exercises Are Safe?