The Effect of Cognitive Task, Gait Speed, and Age on Cognitive-Motor Interference during Walking

Dual task reactive balance control in older adults with mild cognitive impairment: does the cognitive task domain make a difference?

Older adults with mild cognitive impairment (OAwMCI) demonstrate higher cognitive-motor interference (CMI) than cognitively intact older adults (CIOA) during dual tasking. However, studies have rarely examined how dual tasking affects reactive balance control in OAwMCI, or the effect of different cognitive task domains. This study compared how four cognitive tasks affected CMI during reactive balance control in OAwMCI vs. CIOA. In this study, 38 OAwMCI [Montreal Cognitive Assessment (MoCA): 18-25] and 38 CIOA (MoCA ≥ 26) were included and exposed to anterior support surface perturbations in single task and while performing four cognitive tasks: two visuomotor tasks (Target, Track), auditory clock test (ACT), and letter number sequencing (LNS). Cognitive tasks were also completed during unperturbed standing. In both single and dual task conditions, OAwMCI had a higher fall rate and lower reactive center of mass (COM) stability than CIOA. Reactive balance performance deteriorated in both groups while performing Target and Track, although was not affected by ACT or LNS. Cognitive performance was lower in dual vs. single task on the Target, Track, and LNS for both groups, although OAwMCI had higher cognitive costs than CIOA. These findings suggest that dual tasking could increase fall risk in both OAwMCI and CIOA, although visuomotor tasks induced greater CMI than executive function/working memory tasks, suggesting greater sharing of resources with reactive balance control. Furthermore, OAwMCI could experience higher CMI due to damage in sensorimotor areas involved in triggering/executing reactive balance responses, along with multidomain cognitive decline. Comprehensive dual task assessments could identify domain-specific cognitive decline in OAwMCI.NEW & NOTEWORTHY Although OAwMCI have higher CMI than CIOA during volitional balance tasks, it is unclear how dual tasking involving different cognitive domains affects reactive balance control in OAwMCI. This study showed that dual tasking could impair reactive balance responses in both CIOA and OAwMCI, although OAwMCI experienced greater performance deteriorations in dual vs. single task conditions. Furthermore, visuomotor tasks induced higher CMI than executive function/working memory tasks, suggesting greater sharing of resources with reactive balance control.

Dual-task effects of walking-speed on inhibitory control and decision-making under risk

The effect of simultaneously performing two tasks (dual-task effects, DTEs) has been extensively studied, mainly focusing on the combination of cognitive and motor tasks. Given their potentially detrimental impact on real-life activities, the impact of DTEs has been investigated in both healthy individuals and patients. In this Registered Report, we aimed to replicate previous DTEs when a task requiring executive-inhibitory skills is involved while also expanding the evidence on basic facets of decision-making. We recruited 50 healthy young participants who performed a stop-signal task and two gambling tasks (loss-aversion and risk-aversion) while sitting and while walking at three treadmill speeds (normal, slow and fast). We report a significant difference in performance during single-task and dual-task, although with high individual variability. The data show no effect of the walking speed on all the cognitive tasks. Analyses on postural alignments, assessed in the cadence, gait cycle length and stance phase, confirm previous results on cognitive prioritization strategies of healthy individuals. Based on our results, we highlight the need to further investigate prioritization strategies when tasks involving higher cognitive functions are performed along a motor task in healthy individuals and patients with the aim of offering targeted training and rehabilitation protocols. The stage 1 protocol for this Registered Report was accepted in principle on 28/06/22. The protocol, as accepted by the journal, can be found at: https://doi.org/10.17605/OSF.IO/5MWH7 .

The Effects of Cognition and Vision While Walking in Younger and Older Adults

This study investigated how various cognitive tasks and visual challenges affect dual-task walking costs (DTWC) in younger and older adults. Twenty younger adults (Meanage = 22.25, SD = 3.04, 4 males) and eighteen older adults (Meanage = 71.75, SD = 5.17, 7 males) completed single-task walking and dual-task walking. The dual tasks involved walking while performing either (a) serial-subtraction by 3s or (b) a Stroop task. Both single tasks and dual tasks were performed under both normal vision and peripheral-vision-loss conditions. Results showed no significant three-way interaction but two significant two-way interactions: DTWC for step-length was greater during Stroop compared to serial-subtraction, (a) more in older adults regardless of vision (p = 0.022) and (b) more under peripheral-vision-loss regardless of age (p = 0.033). In addition, DTWC for various gait parameters was greater under (a) Stroop compared to serial-subtraction, (b) peripheral-vision-loss compared to normal vision, and (c) older adults compared to younger adults. These findings suggest that, when engaging in a cognitively demanding task, older adults place greater emphasis on maintaining gait compared to younger adults, likely to offset the negative impacts of additional cognitive load and deteriorated vision. Future research should further examine how different cognitive tasks and visual challenges interact across age groups.

Detecting Psychological Interventions Using Bilateral Electromyographic Wearable Sensors

This study investigated the impact of auditory stimuli on muscular activation patterns using wearable surface electromyography (EMG) sensors. Employing four key muscles (Sternocleidomastoid Muscle (SCM), Cervical Erector Muscle (CEM), Quadricep Muscles (QMs), and Tibialis Muscle (TM)) and time domain features, we differentiated the effects of four interventions: silence, music, positive reinforcement, and negative reinforcement. The results demonstrated distinct muscle responses to the interventions, with the SCM and CEM being the most sensitive to changes and the TM being the most active and stimulus dependent. Post hoc analyses revealed significant intervention-specific activations in the CEM and TM for specific time points and intervention pairs, suggesting dynamic modulation and time-dependent integration. Multi-feature analysis identified both statistical and Hjorth features as potent discriminators, reflecting diverse adaptations in muscle recruitment, activation intensity, control, and signal dynamics. These features hold promise as potential biomarkers for monitoring muscle function in various clinical and research applications. Finally, muscle-specific Random Forest classification achieved the highest accuracy and Area Under the ROC Curve for the TM, indicating its potential for differentiating interventions with high precision. This study paves the way for personalized neuroadaptive interventions in rehabilitation, sports science, ergonomics, and healthcare by exploiting the diverse and dynamic landscape of muscle responses to auditory stimuli.

Gait Variability at Different Walking Speeds

Gait variability (GV) is a crucial measure of inconsistency of muscular activities or body segmental movements during repeated tasks. Hence, GV might serve as a relevant and sensitive measure to quantify adjustments of walking control. However, it has not been clarified whether GV is associated with walking speed, a clarification needed to exploit effective better bilateral coordination level. For this aim, fourteen male students (age 22.4 ± 2.7 years, body mass 74.9 ± 6.8 kg, and body height 1.78 ± 0.05 m) took part in this study. After three days of walking 1 km each day at a self-selected speed (SS) on asphalt with an Apple Watch S. 7 (AppleTM, Cupertino, CA, USA), the participants were randomly evaluated on a treadmill at three different walking speed intensities for 10 min at each one, SS - 20%/SS + 20%/ SS, with 5 min of passive recovery in-between. Heart rate (HR) was monitored and normalized as %HRmax, while the rate of perceived exertion (RPE) (CR-10 scale) was asked after each trial. Kinematic analysis was performed, assessing the Contact Time (CT), Swing Time (ST), Stride Length (SL), Stride Cycle (SC), and Gait Variability as Phase Coordination Index (PCI). RPE and HR increased as the walking speed increased (p = 0.005 and p = 0.035, respectively). CT and SC decreased as the speed increased (p = 0.0001 and p = 0.013, respectively), while ST remained unchanged (p = 0.277). SL increased with higher walking speed (p = 0.0001). Conversely, PCI was 3.81 ± 0.88% (high variability) at 3.96 ± 0.47 km·h-1, 2.64 ± 0.75% (low variability) at SS (4.94 ± 0.58 km·h-1), and 3.36 ± 1.09% (high variability) at 5.94 ± 0.70 km·h-1 (p = 0.001). These results indicate that while the metabolic demand and kinematics variables change linearly with increasing speed, the most effective GV was observed at SS. Therefore, SS could be a new methodological approach to choose the individual walking speed, normalize the speed intensity, and avoid a gait pattern alteration.

Dual-Task Interference Effects on Lower-Extremity Muscle Activities during Gait Initiation and Steady-State Gait among Healthy Young Individuals, Measured Using Wireless Electromyography Sensors

To maintain a healthy lifestyle, adults rely on their ability to walk while simultaneously managing multiple tasks that challenge their coordination. This study investigates the impact of cognitive dual tasks on lower-limb muscle activities in 21 healthy young adults during both gait initiation and steady-state gait. We utilized wireless electromyography sensors to measure muscle activities, along with a 3D motion capture system and force plates to detect the phases of gait initiation and steady-state gait. The participants were asked to walk at their self-selected pace, and we compared single-task and dual-task conditions. We analyzed mean muscle activation and coactivation in the biceps femoris, vastus lateralis, gastrocnemius, and tibialis anterior muscles. The findings revealed that, during gait initiation with the dual-task condition, there was a decrease in mean muscle activation and an increase in mean muscle coactivation between the swing and stance limbs compared with the single-task condition. In steady-state gait, there was also a decrease in mean muscle activation in the dual-task condition compared with the single-task condition. When participants performed dual-task activities during gait initiation, early indicators of reduced balance capability were observed. Additionally, during dual-task steady-state gait, the knee stabilizer muscles exhibited signs of altered activation, contributing to balance instability.