Association between frequency of non-minimum toe clearance gait cycles and prefrontal cortex activation during dual-task walking in non-frail older adults

We investigated the association between the frequency of nMTC and the extent of increased PFC activation during dual-task walking.

The study cohort comprised 104 non-frail older adults (aged 71.0 ± 5.8 years, including 67 women) who performed indoor level-ground walking for 3 minutes. Walking was assessed under ST conditions and three DT conditions (verbal task, recall task, and subtraction task). The frequency of nMTC was measured using a 3-dimensional motion analyzer. PFC activation was evaluated with functional near-infrared spectroscopy (fNIRS) to measure oxygenated hemoglobin (HbO₂) levels, and mean HbO₂ levels were calculated for each walking condition for both the right and left PFC. The dual-task cost (DTc), which reflects the degree of cognitive effort, was calculated in each cognitive task. The association between the DTcs of nMTC frequency and both HbO₂ levels in the PFC was assessed using Spearman’s rank correlation coefficient. The significance level was set at 5% for all analyses.

No associations between DTcs of the nMTC frequency and HbO₂ levels both the PFC were found during DT walking with the verbal task, which imposed no cognitive load. However, weak negative correlations between DTcs of the nMTC frequency and HbO₂ levels in right PFC were observed during DT walking with the recall task (ρ = -0.24, P 0.05) and the subtraction task (ρ = -0.21, P 0.05).

During DT walking, increased cognitive-motor interference (CMI) can lead to heightened PFC activation. Consequently, gait automaticity is compromised, and gait control relies more on executive function, leading to the development of nMTC. However, the observed negative correlation between DTcs of the nMTC frequency and the right PFC—rather than a positive correlation—suggests that an increase in nMTC frequency may serve as a compensatory postural strategy to reduce CMI and lower PFC activation.

Although stride length and gait speed are known to decrease in DT paradigms, physically and mentally vigorous older adults may show less pronounced changes. Therefore, in non-frail older individuals, combining these parameters with changes in gait patterns, such as nMTC, can be a useful technique for predicting falls.