Lower limb joint stiffness and muscle co-contraction adaptations to instability footwear during locomotion.
Unstable shoes (US) continually perturb gait which can train the lower limb musculature, but muscle co-contraction and potential joint stiffness strategies are not well understood. A shoe with a randomly perturbing midsole (IM) may enhance these adaptations. This study compares ankle and knee joint stiffness, and ankle muscle co-contraction during walking and running in US, IM and a control shoe in 18 healthy females. Ground reaction forces, three-dimensional kinematics and electromyography of the gastrocnemius medialis and tibialis anterior were recorded. Stiffness was calculated during loading and propulsion, derived from the sagittal joint angle-moment curves. Ankle co-contraction was analysed during pre-activation and stiffness phases. Ankle stiffness reduced and knee stiffness increased during loading in IM and US whilst walking (ankle, knee: p=0.008, 0.005) and running (p<0.001; p=0.002). During propulsion, the opposite joint stiffness re-organisation was found in IM whilst walking (both joints p<0.001). Ankle co-contraction increased in IM during pre-activation (walking: p=0.001; running: p<0.001), and loading whilst walking (p=0.003), not relating to ankle stiffness. Results identified relative levels of joint stiffness change in unstable shoes, providing new evidence of how stability is maintained at the joint level.
School of Sports and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom. Electronic address: C.L.Apps@2013.ljmu.ac.uk.
Charlotte
C
Apps
Li Ning Sports Science Research Center, Li Ning (China) Sports Goods Co. Ltd, Beijing, China.
Thorsten
T
Sterzing
School of Sports and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom.
Thomas
T
O'Brien
School of Sports and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom.
Mark
M
Lake
D000222:Adaptation, Physiological; D000328:Adult; D000843:Ankle Joint / Q000502:physiology*; D001696:Biomechanical Phenomena; D005260:Female; D005684:Gait; D006801:Humans; D007719:Knee Joint / Q000502:physiology; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000502:physiology; D016059:Range of Motion, Articular; D012420:Running / Q000502:physiology*; D012775:Shoes / Q000009:adverse effects / Q000592:standards*; D016138:Walking / Q000502:physiology*
Joint stability; Perturbations; Running; Unstable footwear; Walking