Effects of motor fatigue on walking stability and variability during concurrent cognitive challenges

Abstract

Cognitive-motor interference, a negative influence on the performance of one or both tasks, is manifested when simultaneously performing a cognitive and a motor task. Motor fatigue reduces the ability of generating a required force level. However, little is known about the effects of motor fatigue on the cognitive-motor dual-tasking performance, an important capability during our daily lives. This study investigated how motor fatigue affects dual-task walking performance. Eighteen healthy younger adults walked on a treadmill under three different conditions: walking only, walking while receiving the Paced Auditory Serial Addition Test (PASAT) or a modified Stroop test before and after a lower-extremity fatiguing exercise. We computed dynamic margins of stability (MOS), step and joint kinematic variability, and short-term local divergence exponent (LDE) of the trunk motion. We found that subjects had similar values of short-term LDE during all conditions, indicating that local stability was not affected by the motor fatigue or dual-task conditions. Compared to the baseline, subjects had significantly greater mean MOS after the fatiguing exercise by walking with greater step length and width while having significantly greater gait variability. In contrast, subjects walked with similar mean MOS but significantly less gait variability during the dual-task conditions, indicating that subjects used different adaptive strategies when walking with motor fatigue and during dual-task conditions. There were no significant differences in the number of errors for the two cognitive tests before and after the fatiguing exercise. The current findings demonstrate that motor fatigue does not affect cognitive but motor performance in younger adults.

Minimal effects of age and prolonged physical and mental exercise on healthy adults’ gait

“…2). These results agree with data collected after sustained endurance exercise, showing small (Cohen d: 0.1-0.4) or no effects on stride outcomes, gait variability [28], or on local dynamic stability of foot contact velocity and trunk accelerations [12][13][14] during treadmill walking. In contrast, when older adults walked overground, RSTS did affect stride outcomes and gait variability [9,10].…”

“…However, the joint power generated by the knee extensors compared with the plantarflexors is ˜4 times lower and plantarflexor power correlates (r² > 0.5) with the agerelated decrease in SL and gait speed [32]. These factors support prior data [14], showing the effects of combined knee and ankle fatiguing exercises on gait variability (˜10% increase in variation of the AP and ML margin of stability and SW) and a ˜8% increase in SL.…”

“…In contrast, when older adults walked overground, RSTS did affect stride outcomes and gait variability [9,10]. Repetitive leg-press plus calf and toe rises also increased the average and variability of the margin of stability during treadmill walking at a comfortable speed [14]. The inconsistent results between studies may be due to differences in the assessment of walking (treadmill vs. overground) and models to induce fatigability (muscles, tasks).…”

“…After RSTS, older adults walk overground with 4% shorter stride duration, 2 cm wider steps [9,10], and increase step length and trunk variability [10]. Endurance activity [12,13] and leg press and calf raise exercise [14] produced inconsistent changes in local dynamic stability during treadmill walking.…”

Exploring the role of the left DLPFC in fatigue during unresisted rhythmic movements

“…Thus, it appears that the use of executive resources to carry out Stroop altered the concurrent motor performance of self‐selected FT. However, our study also showed that movement variability in the presence of fatigue was reduced in agreement with previous studies (Cortes et al, 2014; Helbostad et al, 2007; Kao et al, 2018; Morrison et al, 2016; Nagano et al, 2014) but only without Stroop execution. Conversely, in the presence of fatigue, variability increased when subjects' executive resources were engaged in Stroop.…”