Lower limb control and mobility following exercise training

Without sufficient single limb strength, a person cannot transport the body safely and efficiently across terrain because the single limb support or transition takes a significant portion of normal walking. Particularly, a production of adequate ankle joint torque is needed to move the whole body forward safely [1,2]. However, it becomes more difficult as ankle muscle strength and ankle joint flexibility continue to deteriorate with advancing age [3,4]During single limb support, the control applied by the limb is depicted by the joint torque produced for any given joint angle [1,5]. This relationship (the gradient of the torque-angle graph) is named joint stiffness [1,5,6]. Joint stiffness, particularly at the ankle, increases with advancing age [7] and is accompanied with decreases in ankle strength [8]. Degradations in ankle muscle strength or range of motion may result in an increase in ankle joint stiffness leading to unstable gait patterns [7,9-11]. This may increase the likelihood of falls among older adults [2,12].An individual possessing steeper ankle stiffness shows unstable postural balance [7]. The contractile capability of the plantar flexor muscles signifies ankle muscle strength [13], which plays a major role in adjusting the whole body center-of-mass when the postural balance is disturbed such as a slip [14]. Thus, a general decrease in ankle muscle strength with advancing age may interfere with e a person's ability to recover postural balance and may increase the potential for a slip-induced fall. However, little about the effects of ankle joint stiffness on slips has been known. Therefore, the present study aimed to evaluate the role of ankle joint stiffness on the risk of falling among older adults.In addition to ankle joint stiffness, the present study evaluated if limb stability had an effect on the likelihood of a slip-induced fall. Limb stability or control, which has been characterized by variability of gait parameters, may be one of key facto