Previous studies have shown that obesity negatively affects balance during quiet standing, yet little is known about its effect on the ability to recover after a postural perturbation. The purpose of this thesis was to investigate the effects of obesity on single-step balance recovery from an incipient forward fall. Eight obese (BMI = 33.2 ± 2.4) and eight non-obese (BMI = 24.8 ± 1.8) participants were released from a static forward lean and asked to recover their balance with a single step. Lean angle was progressively increased until they could no longer recover balance with a single step. Peak joint torques and relative effort during balance recovery were calculated and compared across the groups. Obese participants achieved a smaller maximum lean angle compared to non-obese participants. During balance recovery, obese participants exhibited higher ankle plantar flexor torques and relative effort. Trends also suggested higher relative hip extensor effort in the obese. Obese adults exhibited a poorer ability to recover from a forward fall with a single step. In addition, obese adults used a higher percentage of their total hip and ankle strength compared to non-obese adults during balance recovery. This suggests that the poorer ability of recovering from a forward fall in the obese may be related to increased exertion levels during balance recovery. / Master of Science

Tripping causes a significant number of falls in the elderly. These falls often result in medical costs, hospitalization, disability, decrease in quality of life, and sometimes death. Knowledge of why trips occur and the mechanics of successful recovery from a trip is critical to increasing knowledge of how to prevent falls due to trips. Two separate studies are reported in this thesis. The first study assessed if men recover from a trip equally well when stepping with their dominant or non-dominant lower limbs. An experimental model of tripping was used to determine each subject's trip recovery capability when stepping with the dominant or non-dominant lower limb. Although most subjects were able to recover better when stepping with one lower limb compared to the other, there was no recognizable trend across the subjects. Based on these results, there is insufficient data to recommend the preferential investigation of the dominant or non-dominant lower limb in future trip research. The second study investigated peak joint torques after stepping to recover from a simulated trip. The same protocol as the first study was used for simulating trips. Increasing trip severity resulted in increased ankle plantarflexor torque in young subjects and increased hip extensor torque in both young and older subjects. Older men used higher hip extensor torques and lower knee extensor torques compared to young men. Implications to falls from trips are discussed. / Master of Science