10 core exercises that are better for your back (and body) than crunches
Pike Crunch (Amazing core workout) - YouTube
TRX Ab Crunch, The best step by step guide you will find in 2019.
FitLife360 - Abs Workout Without Planks or Crunches Pike and Extend Targets: Abs, legs Lie faceup on mat with legs extended over hips, arms overhead. Crunch up, reaching hands toward feet. Keeping