The Effects of Locomotor Task Challenge on the Gait Strategies of Young, Middle-Aged, and Older Adults

The ability to navigate challenging environments is important for independence across the life course. Thus, many studies have examined the differences in gait between young and older adults when navigating challenging terrain. However, it is unknown when these changes occur and if the changes progress systematically with advancing age. Examination of kinematics and kinetics will reveal the strategies and underlying mechanisms associated with age-related changes in a challenging gait task: obstacle crossing. The purposes of this dissertation are 1) to assess how aging affects the ability to deal with gait challenges of increasing magnitude and 2) to identify the joint powers employed to cross an obstacle as a function of age and obstacle height. Gait challenge was examined from two perspectives: increasing difficulty as the participant approached the obstacle within each trial, and increasing difficulty due to obstacle height manipulations. Three age groups were examined: 20–35 year olds (yo) (N = 20), 50-64yo (N=14), and 65–79yo (N = 20). Participants were instructed to walk along a 15 m walkway and step over an obstacle that may be placed in their path. Ten trials of each of the four obstacle conditions (unobstructed, 3 cm, 10 cm, and 26 cm) were conducted. Gait speed of the 50-64yo in the lower task challenge conditions was not different from 20-35yo, but at the higher task challenge gait speed of 50-64yo was not different from 65-79yo. Thus, unobstructed gait and the lower obstacles, insufficiently challenge the balance control system in order to reveal age-related changes in middle-aged adults. Measures related to trunk control, including hip frontal power and step width variability, demonstrated a decline in both 50-64yo and 65-79yo. Therefore, age-related changes that occur in 50-64yo have already compromised trunk control. The ankle joint powers to regulate gait speed demonstrated age-related changes that were not progressive: 50-64yo absorbed and generated less ankle rotational energy than 20-35yo in order to maintain the same gait speed. Generating less ankle energy would reduce instability associated with the piston-like ankle push-off, but gait speed was maintained by decelerating less during mid-stance in the 50-64yo group. Conversely, the 65-79yo absorbed more and generated less ankle rotational energy, resulting in slower gait speed. Additionally, the timing and magnitude of the knee and hip joint powers to accommodate the obstacle demonstrated differential patterns as a function of age. Thus, the control mechanisms are specifically adapted at each age as a function of the goals, such as maintaining gait speed, and the age-related ability, such as the ability to manage instabilities associated with substantial energy generation