The Russian twist is a great underrated ab workout for people of all fitness levels or ages and can be scaled harder or easier with a heavier or lighter medicine ball. Even with no weight at all ...
Start in a plank with forearms on the ground. Rotate to one side, raising the arm towards the ceiling, then return to center ...
For the workout, I recommend one of the best kettlebells for weight training and a medicine ball; this just needs ... stick ...
Sit on the floor with your knees bent and feet off the ground. Hold a weight or medicine ball and rotate your torso from side ...