Cognitive Load Affects Lower Limb Force Time Relations During Voluntary Rapid Stepping in Healthy Old and Young Adults

Background. Quick step execution may prevent falls when balance is lost; adding a concurrent task delays this function. We investigate whether push-off force time relations during the execution of rapid voluntary stepping is affected by a secondary task in older and young adults. Methods. Nineteen healthy older adults and 12 young adults pet-formed rapid voluntary stepping under single- and dual-task conditions. Peak power, peak force, and time to peak force during preparatory and swing phases of stepping were extracted from center of pressure and ground reaction force data. Results. For dual-task condition compared with single-task condition, older adults show a longer time to reach peak force during the preparation and swing phases compared with young adults (similar to 25% vs similar to 10%, respectively). Peak power and peak force were not affected by a concurrent attention-demanding task. Conclusion. Older adults have difficulty allocating sufficient attention for fast muscle recruitment when concurrently challenged by an attention-demanding task.