To ease the massive load on the shoulder-joints, the force must be minimised and the throw be moved away from 'above-shoulder height'.
The way to do this is as simple as it is brilliant.
The technique is based upon a war machine called a trebuchet. This machine have a sling that allows heavy masses being thrown high and far. Utilising the sling you can achieve a far greater momentum in the thrown mass with less force. Some clever trucker took this technique and used it to throw his lashing straps.
To get going you will need a tight-rolled strap. Achieve this with a strap winder.