Association between ankle mobility and gait biomechanics: Effects of sex and age

Abstract

The ankle, as the most distal joint of the lower extremity, makes direct contact with the ground during walking. The primary motion of the ankle occurs in the sagittal plane, and a sufficient amount of ankle dorsiflexion and plantarflexion is required during weight-bearing tasks. For example, during walking, sufficient ankle dorsiflexion is needed for efficient push-off during walking as it is followed by energy release and forward body propulsion. Given the importance of ankle mobility during walking, it is assumed that smaller ankle dorsiflexion capacity may result in abnormal biomechanical adaptations to compensate for the limited capacity. The ankle joint mobility and flexibility can be determined by surrounding musculoskeletal systems of the joint, and the physical characteristics of them have been reported to differ depending on sex and age. Although sex-related differences in gait patterns have been investigated in previous studies, no study has explored the association between the physical characteristics of each sex group such as ankle joint flexibility and their gait patterns. Also, ankle mobility is reduced with aging, but the knowledge of how older adults would adapt to environments that require a larger ankle flexion is limited. Thus, the goal of this dissertation was to understand the association between ankle mobility and gait biomechanics with a specific focus on exploring the effects of sex and age. In the first study, we evaluated the effect of ankle dorsiflexion range of motion on gait biomechanics during incline walking. We found that individuals with smaller ankle dorsiflexion capacity walk with smaller ankle flexion angles but larger muscular loads during incline walking. In the second study, we evaluated the effect of sex on ankle mobility and gait biomechanics during overground walking. We presented evidence that females push off the ground with a larger ankle plantarflexion utilizing their superior ankle flexibility, which enables them to walk with a longer stride and faster walking speed compared to males. In the third study, we evaluated the effect of age on joint kinetics and muscle activation during walking. We quantified activities of leg muscles and ankle and hip joint moments over the 30-min walking trial. We found that older adults exhibit greater muscle coactivation and larger hip joint moments than young adults. In the fourth study, we determined that the effect of age on gait biomechanics is more pronounced than that of sex during incline walking, and older adults’ limited ankle joint function can be compensated by walking with increased stride length, which helps them walk with lower muscular load and energy cost. Together, these four studies provide insight into the association between sex- and age-specific ankle mobility and gait biomechanics during daily walking activities.