Standing upright on stable and unstable surfaces requires postural control. Postural control declines as humans age, presenting greater risk of fall-related injury and other negative health outcomes. Secondary cognitive tasks can further impact balance, which highlights the importance of coordination between cognitive and motor processes. Past research indicates that this coordination relies on executive function (EF; the ability to control, maintain, and flexibly direct attention to achieve goals), which coincidentally declines as humans age. This suggests that secondary cognitive tasks requiring EF may exert a greater influence on balance compared to non-EF secondary tasks, and this interaction could be exaggerated among older adults. In the current study, we had younger and older adults complete two Surface Stability conditions (standing upright on stable vs. unstable surfaces) under varying Cognitive Load; participants completed EF (Shifting, Inhibiting, Updating) and non-EF (Processing Speed) secondary cognitive tasks on tablets, as well as a single task control scenario with no secondary cognitive task. Our primary balance measure of interest was sway area, which was measured with an array of wearable inertial measurement unit sensors. Replicating prior work, we found a main effect of Surface Stability with less sway on stable surfaces compared to unstable surfaces, and we found an interaction between Age and Surface Stability with older adults exhibiting significantly greater sway selectively on unstable surfaces compared to younger adults. New findings revealed a main effect of Cognitive Load on sway, with the single task condition having significantly less sway than two of the EF conditions (Updating and Shifting) and the non-EF condition (Processing Speed). We also found an interaction of Cognitive Load and Surface Stability on postural control, where Surface Stability impacted sway the most for the single task and two of the executive function conditions (Inhibition and Shifting). Interestingly, Age did not interact with Cognitive Load, suggesting that both age groups were equally impacted by secondary cognitive tasks, regardless the presence or type of secondary cognitive task. Taken together, these patterns suggest that cognitive demands vary in their impact on posture control across stable vs. unstable surfaces, and that EF involvement may not be the driving mechanism explaining cognitive-motor dual-task interference on balance.

The purpose of this study was to characterize Cognitive Motor Dual Task (CMDT) costs for a community-based sample of older adults with Motoric Cognitive Risk Syndrome (MCR), as well as investigate associations between CMDT costs and cognitive performance. Twenty-five community-dwelling older adults (ages 60-89 years) with MCR performed single and dual task complex walking scenarios, as well as a computerized cognitive testing battery. Participants with lower CMDT costs had higher scores on composite measures of Working Memory, Processing Speed, and Shifting, as well as an overall cognitive composite measure. In addition, participants with faster single task gait velocity had higher scores on composite measures of Working Memory, Processing Speed, and overall cognition. Taken together, these results suggest that CMDT paradigms can help to elucidate the interplay between cognitive and motor abilities for older adults with MCR.

A growing body of research has shown that static stance control (e.g., body sway) is influenced by cognitive demands (CD), an effect that may be related to competition for limited central resources. Measures of stance control have also been impacted by postural demands (PD) (e.g., stable vs. unstable stances). However, less is known of any possible interactions between PD and CD on static stance control in populations with intact balance control and ample cognitive resources, like young healthy adults. In this study, among the same participants, we factorially compared the impact of PD with and without CD on static stance control. Thirty-four healthy young adults wore inertial measurement units (IMU) while completing static stance tasks for 30 seconds in three different PD positions: feet apart, feet together, and tandem feet. After completing these tasks alone, participants performed these tasks with CD by concurrently completing verbal serial seven subtractions from a randomly selected three-digit number. For two dependent measures, path length and jerk, there were main effects of CD and PD but no interaction effect between these factors. For all other stance control parameters, there was only a PD main effect. Thus, adding a cognitive demand to postural demands, while standing upright, may have an independent impact on stance control, but CD does not seem to interact with PD. These results suggest that young healthy adults may be less sensitive to simple PD and CD due to their greater inherent balance control and available cognitive resources. Future work might explore more complex PD and CD combinations to determine the boundaries under which young adults’ resources are taxed.

No abstract

The motoric cognitive risk syndrome (MCR) is a recently described pre-dementia syndrome in older adults characterized by slow gait coupled with subjective cognitive complaints. While previous studies have demonstrated the benefits of exercise on cerebral hemodynamics in healthy older adults, to date, no study has characterized the effects of exercise on these parameters among more vulnerable older persons with MCR. To address this knowledge gap, we investigated how the brain area responsible for high-order cognitive function (i.e., prefrontal cortex) is affected during acute cycling exercise in 19 older adults with MCR (Age (mean ± SD): 73.7 ± 7.1 years; BMI: 32.1 ± 5.5 kg/m2; gait speed: 0.55 ± 0.1 m/s; Modified Mini-Mental score: 91.8 ± 6.8; 74% female). Participants performed an incremental submaximal cycling test and we used functional near-infrared spectroscopy to assess changes in concentrations of Oxyhemoglobin (O2Hb), Deoxyhemoglobin (dHb) and total hemoglobin (Hbt) during exercise. Results showed that participants cycled for 4.9 ± 0.5 minutes, achieved a submaximal load of 54.7 ± 17.3 watts, a peak exercise heart rate of 95.7 ± 14.7 beats/min and a rate of perceived exertion (13.8 ± 2.0). Compared to baseline, there was an increase of 97.3 % in the O2Hb, 86 % on the Hbt and an 87.9 decrease of dHb while exercising. Our findings suggest that acute exercise at light through moderate intensity increases prefrontal cortex oxygenation in older adults with MCR. Additional studies are also warranted to characterize the effects of chronic exercise on cerebral hemodynamics in at-risk older adults.