Posted By Jane Blunt We did a tug-of-war in Science week, with teams of children trying to pull apart a replica of Magdeburg hemispheres. This had restraining bolts in case they succeeded (which they did not). Go to this address to find out the science: http://www.darvill.clara.../enforcemot/pressure.htm However, to return to the point I had to worry about two key aspects: the strength of the rope, and what would happen if the children were to fall over. The rope was easy - you just work out the maximum force and buy accordingly. We spaced the children out so that they would not fall on top of one another. We did it on soft grass (it was soft in March) so that the landing would not be too hard. Children tend to fall over quite a bit as part of everyday life, so the risk of injury to them is small (I speak as an experienced judo coach). They were well supervised and controlled - in particular instructed when to stop pulling. Doing a risk assessment for adults is more difficult. Those who are young and fit and play games like rugby would be at very low risk of injury, but older less fit individuals are a very different matter. However, whatever injury you may get if you fall over is likely to be multiplied if someone lands on top of you, so my original control measure has a lot going for it. If you fall over, the most vulnerable part of the body is the head, and most, but not all, people have an instinct to keep their head off the ground. This usually works if they are falling under gravity (but as all novice judo players know does not always work if you are thrown on the floor!!). If both hands are on the rope they are unlikely to reach down to break their fall and break their wrists or collar bone. I guess the over enthusiastic might scuff a small hole in the ground to give them a better purchase with their heels and then might break their ankle as they get dragged out of it. When your back hits the floor, little injury is likely in a relatively fit person. You could get winded, but although this can be very painful it is not an injury and you do get better. Good luck! Jane