These 240 not able-bodied volunteers will be selected using the same inclusion/exclusion criteria and standardized medical histories and physical examinations as above. One exception to the exclusion criteria is that if a not-normal participant uses ongoing medications for control of discomfort, it will be left to the discretion of each investigator as to how that individual’s medication profile may affect their pain reporting, physical performance, or compliance with the protocol steps. A 3-day medication “wash-out” will be allowed (and encouraged) if there is any concern about a participant’s performance.