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-up - Wikipedia
Sit-Ups, Crunches, Planks, Knee-Ups: The Evolution of Core Fitness
Forget sit-ups — 10 best crunches and variations to…
The Truth about Whether You Should Crunch or Plank Your Way to a
How to Do a Sit Up Correctly, Abs and Core Exercises
The best core exercises to do at home
Training the core for performance
5 Oblique Exercises for Stronger Core and Spine Support
Planks Vs Sit-Ups – Your Ultimate Guide – Sport Science Insider