Date of Award
Master of Science (MS)
In human walking, balance control is managed through proactive changes in spatio-temporal parameters of stepping . It has been suggested that continuous disruptions to healthy young adult balance cause greater changes to overall variability of these parameters than a shift in the mean stepping parameters . This suggests that walking may be occurring in a more reactive manner, modulating to maintain balance without increasing the mean significantly. Work using continuous oscillations to treadmill walking suggest there is an interplay between the predictability of a signal used to disrupt subject balance and the degree to which compensation occurs . To determine how balance compensation occurs during continuous, unpredictable oscillations this work investigated the effects of unpredictable oscillations on human walking. A 6 Degree of Freedom Motion base was used to oscillate 12 subjects walking on a treadmill for seven different balance conditions: (1) Normal Walking (2) Pitch Amplitude Oscillations, (3) Pitch Frequency Oscillations, (4) Roll Amplitude Oscillations, (5) Roll Frequency Oscillations, (6) Medial-Lateral Amplitude Oscillations, and (7) Medial-Lateral Frequency Oscillations. Amplitude perturbations used a probabilistic multiplier to change the amplitude of an applied sine wave each period, maintaining timing, while frequency perturbations used the same multiplier to vary the timing of sine waves for each period. Amplitude oscillations caused a greater degree of proactive control characterized by changes in temporal stepping parameters. Frequency oscillations resulted in a greater change in reactive control, demonstrating variability in stepping parameters immediately preceding and following peaks in accelerations peaks which exceed 0.5 m/s2. These observations suggest that healthy young adults shift to a reactive strategy of balance compensation when subject to more difficult, higher acceleration oscillations of support surface while maintaining a proactive rate of level walking at low accelerations.