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.

Sit-Ups Benefits: Exercises, Variations, and More

20 Best Core Workouts For Women - Core Exercises For Stronger Abs

Planking is in, situps out for Navy physical readiness test

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

Core Training. Suppose you want to tone your abdominal…

The Major Differences Between Sit-Ups and Crunches

Sit-Ups Benefits: Exercises, Variations, and More

Fitness Experts: Sit-Ups Are Worthless, Here's What to Do Instead

How to Do Crunches Correctly — Plus 14 Variations