Just saw this,square cage with four rollers,lay on your back,place your heels in.Raise your hips,begin curling your heels.I had one of the original Total Body devices,you could hook your heels under a strap and pull your body weight up with a hamstring curl,elevating the hips very much intensifies this movement.You can use bands or hold a weight to increase resistance.US 129 is a steal for what this movement can do for you.Don’t care what else you ave been doing,this movement is extreme.
Https://www.sorinex.com/product/sorinex-glute-ham-roller/
Https://www.sorinex.com/product/sorinex-glute-ham-roller/