Instructions limiting the number of steps do not affect the kinetics of the threshold of balance recovery in younger adults

To our knowledge, no one has explored the effect of modifications in balance recovery instructions on the kinetics of the threshold of balance recovery. In particular, the effect of instructions limiting the number of steps on joint torques at the maximum lean angle has not been quantified. We determined the joint torques at the ankle, knee and hip of 28 younger adults recovering balance at their maximum lean angle using: (i) only a single step, (ii) no more than two steps and (iii) no limit on the number of steps. Results showed that instructions limiting the number of steps did not affect peak normalized joint torques by more than 0.0083 or 10 N m except for knee and hip flexion torques from first to second heel strike for the first step leg as well as from second toe-off to heel strike for the second step leg. However, these large differences in peak normalized joint torques after the first step were simply caused by the additional steps used when participants could take more than one step compared to when participants were limited to only a single step. Between the three limits on the number of steps, the kinetics of both legs were nearly identical up to the end of the first step and the additional steps did not help to increase the maximum lean angle. Therefore, we have demonstrated that instructions limiting or not limiting the number of steps appear to be equally valid to study falls in younger adults.