Effects of aerobic fitness on dual task walking in older adults

Having higher aerobic fitness levels leads to better cognitive performance and increases in the oxygenation of the prefrontal cortex (PFC) (i.e., increase in PFC activation patterns). Unfortunately, it is unknown how aerobic fitness levels can affect these measures while dual-task walking. Additionally, the relationship between aerobic fitness levels and cognitive motor interference (CMI), which is a direct of measure of dual-task performance related to falls in older adults, has not been examined. It is important to understand these relationships because falls related to dual-task walking is very common in older adults and causes major consequences that negatively affect their quality of life. Thus, the objective of this dissertation was to examine the encompassing effects of aerobic fitness on dual-task walking in older adults by examining cognitive motor interference, cognitive performance, and changes in PFC activation patterns. For the studies included in the dissertation, depending on the study design, the sample size differed (i.e., 24 vs 34 participants) and different tasks were incorporated (i.e., single task walking, dual-task standing, or dual-task walking). All studies involved assessing aerobic fitness levels with the Rockport 1 mile walk test and performing the Modified Stroop Color Word Test on a self-instrumented treadmill. Gait speed dual-task cost was used to measure CMI and the Stroop Interference was used as the measure for cognitive performance. Chapter 1 found that lower fit individuals exhibited higher dual-task cost than the higher fit individuals when going from single-task walking to dual-task walking. Furthermore, when compared to the easiest dual-task Stroop condition, all participants exhibited decreases in dual-task cost during the other dual-task walking conditions with increasing difficulty. Chapter 2 found that individuals with lower estimated VO2max scores exhibited lower cognitive performance (i.e., greater SI) while dual-task walking when compared to individuals with higher estimated VO2max scores and dual-task standing in a moderately difficult Stroop condition. Additionally, during the most difficult Stroop condition, individuals with lower estimated VO2max scores exhibited greater SI while both dual-task walking and dual-task standing. Chapter 3 found that lower fit individuals exhibited greater decrements in recruitment of PFC activation (i.e., greater changes in PFC when going from single-task walking to dual-task walking) during the most difficult Stroop condition when compared to higher fit individuals and the easiest Stroop condition. Additionally, the fitness level groups only differed in PFC activation patterns while dual-task standing with a moderately difficult Stroop condition. Overall, the findings from this study indicated that while dual-task walking, individuals with lower fitness levels or low estimated VO2max scores exhibited greater decrements in physical and cognitive dual-task performance and greater recruitment of attentional resources which is consistent with the neural efficiency model. As a whole, these study’s findings add to the current literature establishing the beneficial effects of aerobic fitness for dual-task walking. While this study was the first to examine the overall effects of aerobic fitness on measures directly and indirectly related to dual-tasking, no causal relationships can be formed. Thus, it is recommended for research to examine the effects of an aerobic intervention program on these measures in older adults. Such findings will elucidate the importance of aerobic fitness in older adults to improve dual-tasking ability and decrease the risk of falls