Get ready to light those abs on fire with this killer exercise! A bent knee jackknife is perfect for working both the rectus abdominis and the obliques to get them nice and toned- which also means flat.
Get ready to light those abs on fire with this killer exercise! A bent knee jackknife is perfect for working both the rectus abdominis and the obliques to get them nice and toned- which also means flat.
Fey Fitness 