Obstacle negotiation kinematics: age-dependent effects of postural threat

Abstract

DEDICATIONI dedicate this thesis to my Poppa, John Joseph Lacey. You have taught me the meaning of dignity.iii ABSTRACTThe effects of postural threat and the potential consequences of obstacle contact on the obstacle negotiation kinematics among younger and older adults were examined. Seventeen older (OA; 7 males, 10 females; mean age, 68.94 ± 4.85) and fifteen younger adults (YA; 5 males, 10 females; mean age, 22.53 ± 2.77) negotiated virtual and real obstacles while walking at a self-determined velocity along a 7.2m walkway under 4 different conditions of postural threat. Postural threat was manipulated by varying the width (0.60m versus 0.15m) and height (floor versus elevated (0.00m versus 0.60m)) of the walkway. Postural threat altered crossing kinematics for all subjects. Specifically, age-related differences emerged with increasing postural threat, however die changes observed among older adults were considerably different from those of younger adults. Additionally, there was an effect for the potential consequences of obstacle contact, however, no age-related differences emerged. These results revealed an effect for postural threat and obstacle characteristics on the negotiation strategies of younger and older adults. Both postural threat and obstacle characteristics elicit conservative crossing kinematics in younger and older adults. Specifically, these findings illustrate age-dependent differences in obstacle negotiation strategies and that postural threat affects older adults differently than younger adults whereas the potential consequences of obstacle contact affects younger and older adults equally. iv ACKNOWLEDGEMENTSWe did it! This thesis would not have been possible without die support of my family and friends. I would like to show my appreciation to everyone who encouraged and stood by me during the creation of this thesis.

Interactions of age and leg muscle fatigue on unobstructed walking and obstacle crossing

“…Similar to unobstructed level ground walking this coincided with an increased gait speed and a tendency toward an increase in step length. The latter findings appears to be in contrast with previous studies on obstacle crossing in which it was found that step length and gait speed decreased in the presence of a postural threat [27]. This suggests that the present findings cannot simply be interpreted as the consequence of an increase in postural threat experienced due to leg muscle fatigue, but are more specific to the fatigue experienced by the individual during the experiment.…”

Obstacle crossing deficits in older adults: A systematic review

“…Of the 13 studies that reported spatiotemporal data, five reported no difference in spatiotemporal variables between young and older adults [17,[22][23][24][25]. In the eight that reported differences, older adults walked slower during obstacle crossing [13,14,15,20,21,26], with smaller steps [13,14,18,21]. Older adults landed closer to the obstacle with their lead limb after crossing in three studies [14,21] however, only a significant difference between older and younger females was reported in the study by Chen et al [20].…”

Biomechanical aspects of dynamic stability

“…Stepping is necessary if there is sufficiently high velocity of the COM, even if the COM is located within the BOS at step initiation. Older adults employ a rapid stepping response compared to young adults under the same conditions because such stepping responses are less threatening to loss of balance [29,38].…”