Walking difficulty is common and costly in older adults. While traditional exercise has been shown to promote physical and mental health and may prevent walking difficulty, such exercise has focused on strength and endurance, and has overlooked a critical component of walking ability; the timing and coordination of movement. Aging and disease alter timing and coordination as reflected by slowed neuromotor performance, increased gait variability and reduced smoothness of movement. Task specific timing and coordination exercise that includes practice of smooth coordinated aspects of gait over multiple walking conditions has the potential to improve walking ability greater than a standard program. Our preliminary data suggest that interventions on timing and coordination of gait impact mobility greater than the standard strength and endurance program. The next key step and the objective of this proposal is to combine the two interventions to determine if potential gains in mobility, activity and participation obtained from a standard plus timing and coordination program, are larger than the gains obtained from the standard program alone. Therefore, the primary aim of the proposed project is to evaluate the impact of adding timing and coordination training to standard strength and endurance training on mobility. Secondary aims include examining 1) additional outcomes representing the components of the intervention and measures of activity and participation, 2) the delayed and sustained effects of the intervention, and 3) the effects of the intervention within various other subgroups of interest. This randomized clinical trial in older adults who walk slowly (i.e. < 1.20 m/s) will compare a 372 community-dwelling non-intervention attention control and a standard 12 week strength, endurance and flexibility program to a 12 week standard- plus program of strength, endurance, flexibility plus task specific timing and coordination training. The primary outcome is gait speed at 12 weeks. We will also examine secondary and tertiary outcomes representing components of the intervention and measures of activity and participation and the delayed and sustained effects at 24 and 36 weeks. The findings from this efficacy trial will provide evidence for the added value of task specific timing and coordination training for promoting walking ability in older adults and will form the basis for future effectiveness trials. Future work includes translation to nonprofessional exercise leaders with the long-term goal to incorporate neurological training into standard exercise programs for health promotion for older adults.