Apart from BA's lame response i still hear no legit argument as to why wearing a helmet or seatbelt is something that infringes on your rights?
Most people are referencing "negative rights" which IIRC was part of this country's philosophical foundation under Jefferson, et al. A negative is a right not to be subjected to an action of another person or group. Whether the negative theory of rights is supported in practice, deed, or action by those drafting & enforcing the laws is not really consequential.
People will say, about seatbelts, for example, that without them our insurance rates would be higher or our health care costs would be higher (negative externalities) and therefore to keep one man from imposing these "costs" on others, it is necessary and justifiable to make everyone wear the seatbelt. Well there may not be any evidence to suggest insurance rates would be higher (they didn't go down in the mid 1980s when seatbelt laws gained traction in the US) and as for health care costs, a case could be made that this argument is untenable as question-begging.