 Volunteers in this study will be asked to do the following: 1 complete a series of questionnaires about health status and undergo physical screening of neck to make sure that manipulation will not be harmful; 2 walk in socks or bare feet across a computerized mat under 3 conditions - normal walking pace, walking while looking up and down repeatedly; and walking while looking left and right repeatedly; 3 have one of 2 manual therapy interventions to the neck; 4 repeat the walking across the computerized mat under those same 3 conditions. 