The brain in motion—cognitive effects of simultaneous motor activity

Research on how motor activity influences cognition has traditionally focused on asynchronous effects (e.g., regular exercise reducing cognitive decline), but recent work examines simultaneous motor activity as the natural context for human cognition. Behavioral measures (reaction time, accuracy, kinematics) and neuroimaging (fMRI, MEG, EEG) each provide different windows into these processes, with EEG enabling more natural movement but facing motion-related artifacts. The review builds on Cantelon and Giles (2021) to compare behavioral and EEG studies during concurrent movement. Competing theories include physiological accounts: (1) arousal hypothesis predicting an inverted-U relation and benefits at moderate intensity; and (2) hypofrontality theories proposing executive benefits up to certain intensity/duration but potential collapse beyond. Psychological accounts include: (3) Attentional Resource Hypothesis (posture-first strategy) predicting cognitive decrements under dual tasks; and (4) entrainment theory suggesting rhythmic movement provides temporal templates that can facilitate information processing. The review aims to synthesize findings across methods, highlight poor comparability, and suggest directions for future EEG research.

Two meta-analyses (Lambourne et al., 2010; McMorris & Hale, 2012) showed that acute exercise effects depend on cognitive domain, intensity, modality, and duration, with benefits often seen for speeded executive processing at moderate intensity and during cycling more than treadmill running, especially with durations >20 min. Behavioral studies have systematically manipulated these parameters, whereas EEG studies have prioritized methodological feasibility (recording reliable ERPs under movement) and thus often limited modality, duration, and intensity. Theories reviewed: arousal (inverted-U), hypofrontality (transient/reticular-activating), attentional resource/posture-first, and entrainment/synchronization frameworks. Subsequent sections summarize behavioral evidence by cognitive domain (executive vs non-executive) and compare with EEG findings, noting discrepancies likely driven by modality (frequent walking in EEG), short durations, and light intensities.

Selective narrative review of dual-task experiments in healthy adults (18–50 years), comparing cognitive task performance during continuous physical activity (large muscle groups engaged) versus sedentary single-task controls. Studies through April 24, 2023 were identified via PubMed, Google Scholar, and reference lists using combinations of key terms (acute, simultaneous, during, exercise, motor activity, physical activity, movement, walking, running, cycling, pedaling, EEG, event-related potential, cognition, cognitive function, oddball, etc.). Experiments that compared exercise intensities without sedentary controls were excluded. A total of 79 publications covering 88 studies were retrieved. Intensity categories followed ACSM guidelines: very-light (<37% VO2max or <57% HRmax), light (37–45% VO2max or 57–63% HRmax), moderate (45–63% VO2max or 64–76% HRmax), vigorous (64–90% VO2max or 77–95% HRmax), near-maximal to maximal (≥91% VO2max or ≥96% HRmax). The intent was not a systematic review or meta-analysis but a comprehensive state-of-the-art synthesis and recommendations for future research.

Behavioral studies: 60 studies comparing movement with rest showed 34 positive, 13 negative, and 13 mixed/null effects. Durations among 54 studies: 24 lasting 15–30 min, 17 <15 min, 7 for 31–45 min, and 6 >45 min. Executive functions: cognitive inhibition results mixed, with moderate-intensity cycling often improving reaction times; vigorous exercise or walking/running can impair accuracy. Motor inhibition largely benefited from cycling at light to moderate intensities (with one vigorous treadmill study showing decrements). Cognitive flexibility consistently improved with short light walking (treadmill or free). Working memory was mostly impaired or unaffected (about 80% showing no effect or impairment), with decrements reported for vigorous treadmill and light free walking; some benefits appeared in short moderate-intensity cycling and long moderate cycling. Non-executive functions: attention findings mixed (58% positive), generally faster RTs with moderate cycling; vigilance mostly benefited (approximately 75% positive) across intensities and durations, including prolonged running; long-term memory showed mixed results, with positive effects commonly seen around ~30 min exercise, often at moderate intensity, and sometimes when motor activity could synchronize with stimuli. Modality: of 13 walking/running studies, 61% reported negative or null effects; among 48 cycling studies, 60% reported positive effects. EEG studies: 29 studies reviewed; many used walking (more than half) and short durations (<15 min in over half). Attention-related ERPs (primarily P300 in oddball paradigms) often decreased during walking (outdoor or treadmill), with mixed or null findings during cycling. Inhibition-related EEG results were heterogeneous (mixed, negative, and some positive), with moderate/light cycling sometimes increasing P300 and improving RTs. Vigilance EEG during walking showed mixed results; cycling studies often showed null effects for ERPs over short durations. Overall, discrepancies between behavioral and EEG outcomes appear driven by modality (frequent walking in EEG), shorter EEG activity blocks, and predominance of light intensities. Trends: moderate intensity and cycling tend to benefit basic processing (vigilance, motor inhibition), while walking may broaden attentional focus and impair tasks requiring narrow focus (e.g., selective attention, some working memory).

Behavioral and EEG studies differ in aims and design, complicating direct comparison. EEG studies prioritize methodological viability (robust ERPs under motion, artifact handling) and thus often use short, light-intensity walking paradigms, whereas behavioral studies are more theory-driven and vary intensity, duration, modality, and cognitive domain. This mismatch likely underlies the observed discrepancy (behavioral benefits vs EEG decrements). The review argues for theory-driven EEG designs that systematically compare modalities (cycling vs treadmill walking vs sitting) under matched, controlled indoor conditions and manipulate duration and intensity to assess when movement supports or impairs specific processes. EEG’s temporal resolution can reveal which processing stages are affected even when behavior is unchanged. Analytical approaches should consider potential changes in ERP topography during movement (favoring cluster-based permutation tests over fixed ROIs). Conceptually, the authors propose that movement is a natural cognitive state; dual-task costs arise when motor activity does not match the cognitive process’s attentional demands. Free walking may broaden attentional focus and thus impair tasks requiring narrow focus (e.g., selective attention oddball), while stationary cycling, especially with motor-synchronization to stimuli, may narrow attentional focus and facilitate encoding and selective processing (consistent with entrainment theory). This matching framework explains heterogeneous outcomes across domains (e.g., walking aiding cognitive flexibility; cycling benefiting inhibition and some long-term memory encoding).

This narrative review synthesizes behavioral and EEG evidence on concurrent motor activity and cognition, highlighting heterogeneous outcomes and methodological differences that hinder comparability. Behavioral data suggest benefits for vigilance, motor inhibition, and cognitive flexibility, with moderate-intensity cycling often advantageous; working memory frequently shows no benefit or impairment. EEG studies, dominated by short-duration walking paradigms, commonly report reduced attention-related ERPs during movement. The authors recommend theory-driven EEG research with controlled indoor comparisons of modality, duration, and intensity, and analyses suited to potential movement-related ERP topography changes. They propose a task–movement matching framework based on attentional focus and entrainment, where synchronized, stationary movement may support tasks requiring narrow focus, while free walking may benefit tasks relying on broader focus (e.g., flexibility). Future work should include long-term memory with simultaneous EEG to disentangle encoding vs retrieval effects and systematically test synchronization as a mechanism.

Selective narrative review rather than a systematic review or meta-analysis; heterogeneous study designs and limited comparability between behavioral and EEG paradigms (e.g., modality, duration, intensity). EEG studies often constrained to short, light-intensity walking, with potential motion artifacts (sweat, impedance changes) and environmental confounds in outdoor/free walking (variable visual input, obstacles, observation by passersby). Some cognitive domains (e.g., cognitive flexibility, motor inhibition) had relatively few studies; long-duration paradigms were less common; and long-term memory has not been studied with simultaneous EEG.