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

The 10 Best Sit-Up Alternatives for a Stronger, More Powerful Core

Crunches vs. Sit-Ups: Is One Better for Strengthening Your Core?

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

Intentional breathing in a core training programme - Sportsmith

Straight Legged Sit Ups Can Make You A Fitness Beast, A Complete Exercises Guide

5 Oblique Exercises for Stronger Core and Spine Support

Say Goodbye to Sit-Ups: 7 Ab Exercises That Are Even Better for Your Core

Why You Can Stop Doing Sit-Ups - WSJ

Training the core for performance

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

Sit-ups and Back Pain

Planks or Sit-ups for Sports Performance? — CoachMrFoster