Found this out by accident this morning when cleaning my blender cup.

Take your blender cup with the metal ball in it and fill it 1/2 way with Water. Turn it side ways and grab the ends with both hands. Stand up straight, hold your core tight and shake vigorously from side to side in a horizontal plane for 5 minutes. It gives your core and lower back an invigorating workout. You want to makes sure the ball hits the edges as you go from side to side in a fast and rhythmic fashion. Should I patent it as a made for tv gizmo All kidding aside, it makes for a brain dead simple exercise. You may be able to increase intensity by filling with more water, a more liquid with more viscosity or by increasing the rate of oscillation. Have fun!

Umm, like this: https://www.shakeweight.com/

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Yes, a little like the shake weight as you have pointed out. I guess my suggestion is the poor man's solution.

Umm' date=' like this: https://www.shakeweight.com/[/quote']

Hehe