Date of Award

December 2014

Degree Type


Degree Name

Master of Science



First Advisor

Stephen C. Cobb

Committee Members

Kristian O'Connor, Kevin Keenan


Biomechanics, Curb, EMG, Multi-Segment Foot Model, Stair


Ankle injuries are common during activities of daily living, particularly in negotiation of steps. Previous studies examining steps have generally focused on the ankle, knee, or hip and descent of multiple steps. Joint motion within the foot, utilizing a multi-segment foot model, during step descent has not been extensively studied. Although peroneal muscle activity differences have been identified between participants with healthy and unstable ankles during static activities, little is known about peroneal activity during activities of daily living. A better understanding of the foot kinematics and muscle activity in persons with uninjured ankles may help future studies elucidate the problems encountered by individuals with chronic ankle instability during step descent. Therefore, the purpose of this study was to identify the foot and ankle kinematics and lower extremity muscle activity of uninjured individuals during descent from varying step heights. Twenty-two participants (12 female/ 10 male, 25.68 ± 5.5 years) walked on a level walkway, stepped down a single step of varying heights (5 cm, 10 cm, 15 cm, 20 cm and 25 cm) and continued walking on level ground. Data acquisition included walking gait kinematics, utilizing a six-segment foot model, and peroneal muscle activity recorded with surface electromyography. Three-dimensional kinematics (initial contact angle, range of motion) across the five step heights from initial contact to the end of weight acceptance were analyzed via RM MANOVAs. Paired t-tests were used to compare muscle activity during the 200 ms prior to initial contact between each step height.

Results demonstrated a greater percentage of participants preferred to switch initial contact from a heel strike to a forefoot strike as step height increased. The calcaneonavicular complex had significant differences in initial contact angle in the transverse plane between the 5-cm step and steps of 20 and 25 cm. Range of motion differences were not significantly different across any of the step heights. Integrated electromyography differences were significant between the 5-cm step and the 15, 20 and 25-cm step heights; between the 10-cm step height and the two highest steps; as well as between the 15-cm and 20-cm steps. These results indicate stability of the medial midfoot and medial longitudinal arch may become more dependent upon dynamic stabilizers as step-down height increases and/or landing strategy transitions from heel to forefoot.

Included in

Kinesiology Commons