SUDDEN TURNS AND STOPS WHILE WALKING - KINEMATIC SOURCES OF AGE AND GENDER DIFFERENCES

Background: Significant age and gender differences were found among he althy young and older adult subjects in their abilities to quickly tur n or stop in order to avoid obstacles that suddenly appear in the gait path (Cao C, Ashton-Miller JA, Schultz AB, Alexander NE. Abilities to turn suddenly: effects of age, gender and available response time. J Gerontol Med Sci 1997;52A:M88-M93; Cao C, Ashton-Miller JA, Schultz AB , Alexander NB. Abilities to stop suddenly: effects of age, gender, ga it phase, and available response time. Submitted for publication, 1997 (also available as a chapter in Cas C. Biomechanics of forward moment um arrest when walking: age and gender differences. PhD Dissertation, University of Michigan, 1996). The present study quantified the extent to which age and gender differences in those subjects' response kinem atics affected the total time they needed to suddenly arrest their for ward momentum. Methods: Age- and gender-group means of four measures o f forward movement of the anterior surface of the abdomen were obtaine d: the duration of the first post-cue response phase, from the visual cue that initiated the arrest response to reaching peak velocity (T-1) ; acceleration (A(1)) during this phase; and decelerations (D-2 and D- 3) during two subsequent post-cue response phases. A three-line-segmen t representation of this forward velocity history was constructed. Thi s representation was used to predict the differences in response time needed (NRT) to suddenly arrest momentum that resulted from measured a ge and gender differences in each of the four response kinematics meas ures. Results: The largest contributor to the age group difference fou nd in NRT was the increase in T-1 among the older adults. Among the ol der males, the next largest contributor was their larger value of A(1) , and among the older females, their substantially smaller value of D- 2. Among the young adults in sudden turns, no single kinematic paramet er seemed primarily responsible for the gender difference found in the NRT. Among the older adults, the gender difference in D-2 was almost fully responsible for the gender difference in NRT, in both sudden sto ps and turns. Conclusions: Much of the older adults' need for longer r esponse times than those of the young was attributable to the lengthen ed first phase of their responses. Older females, in addition, needed longer response times than young adults or older males because, during the second phase of their responses, their decelerations were substan tially smaller. These age and gender differences may have arisen in pa rt from known age and gender differences in abilities to develop lower extremity joint torque strengths rapidly. (C) 1998 Elsevier Science B .V.