Have a lawyer draft a release stating that the customer understands the risks in engaging in your serivces and by agreeing to the aforementioned also agrees that you as the service provider are no liable for any accident or injury.

I cannot emphasize this enough, it is well worth the money to have a lawyer draft a release. The smallest error or loophole which can be interpreted will cost you if you every do get sued.

The way you do it is by hiring an attorney who is thoroughly versed in contract law to draw up such an agreement for you. Even then, a judge in a court of law would have the final decision as to whether or not you’re liable.

Visit an EXISTING company in a similar business and obtain a copy the the agreement THEY use. It is not as good as hiring an attorney, but better than any other options.

Merely stating that you are not liable does not make you not liable. The courts will decide that according to law in any specific case.

If it were me, I would probably start by getting the customers to fill in some sort of medical questionaire, which would include things like brittle bone disease, but accepting physically fit clients would only reduce the risk of injury (and getting sued). It would not eliminate it altogether.