A Review of Acute Physical Activity Effects on Brain and Cognition in Children

The prevalence of physical inactivity in children has become a global pandemic and has consequences for physical, as well as cognitive and brain, health. Single bouts of physical activity (PA), however, have shown a transient, positive effect on cognitive performance in preadolescent children. Acute bouts of moderate to vigorous PA have demonstrated benefits for cognition, including attention and executive function. These acute effects of PA on cognitive performance can be seen both immediately after and following a delay from the cessation of PA. Further, event-related potentials have been used to delineate real-time neural responses to behavioral tasks after PA interventions. A short bout of moderate-intensity aerobic PA serves to increase the allocation of attentional resources and improved cognitive processing and stimulus classification speed. As such, there are implications for evaluating the effect of PA within schools. Several neural mechanisms are suggested to explain the observed improvements in executive function after PA, such as the importance of brain-derived neurotrophic factor on synaptogenesis, the expression of human growth factors, the activated release of catecholamines, and increased blood lactate levels. The ensuing descriptive review demonstrates the current understanding of the effects of acute PA on childhood brain and cognition and may serve as a basis for understanding PA-induced improvements in academic achievement. INTRODUCTION In an era where physical inactivity has become a global pandemic (1), adverse effects have been observed not only for children’s physical health (2) but also their psychosocial well-being (3). Only 1/3 of boys and 1/5 of girls in Western countries are physically active at the recommended levels to optimize their health (i.e., >60min of daily moderate to vigorous physical activity (PA); (4)). The shift to a more sedentary lifestyle is contrary to our evolution as a physically active species; thus, our genetic makeup is maladapted to the sedentary lifestyle of today (5,6). As such, sedentary behavior represents a physiological disjunction from healthy (i.e., physically active) behaviors and has implications for poorer cognitive and brain health (7). Northeastern University, Boston, MA Address for correspondence: Charles H. Hillman, Department of Psychology, Northeastern University, 635 ISEC, 360 Huntington Avenue, Boston, MA 02115 (E-mail: c.hillman@northeastern.edu). 2379-2868/0417/0132–0136 Translational Journal of the ACSM Copyright © 2019 by the American College of Sports Medicine 132 Volume 4 • Number 17 • September 1 2019 Copyright © 2019 by the American College of Sports Medicine. Unauthorized repro Although children in industrialized countries are growing increasingly inactive and unhealthy, the investigation of the effects of PA on cognitive and brain health during development has only recently been recognized. A recentmeta-analysis observed that single bouts of PA had a small, positive effect on cognitive performance regardless of whether cognition was assessed during PA, immediately after PA, or following a delay after PA (8). Further, several factors moderated this effect, with PA intensity characterized as“moderate” to“very hard,” a delay of 11–20min after PA, PAbouts of at least 20 min in duration, and tasks that tap executive control engendering the largest effects on cognition. Several other metaanalyses (9–13) have corroborated the findings of Chang et al. (8). Collectively, these findings suggest that single bouts of PA promote transient benefits to cognition. To that end, the recent findings from the 2018 Physical Activity Guidelines Scientific Report (14) summarized this literature and indicated that strong evidence was available demonstrating that acute bouts of moderate to vigorous PA have a transient benefit for cognition, including attention, memory, crystallized intelligence, processing speed, and executive control during the postrecovery period after a bout of PA. The findings indicated that the effects are larger in preadolescent children and older adults relative to other periods of the life span (pp. F3–5; https://health.gov/paguidelines/secondedition/report/pdf/PAG_Advisory_Committee_Report.pdf). The relatively recent advent of neuroimaging techniques has facilitated the investigation of the neural underpinnings of acute PA effects on cognitive processing. In particular, electroencephalography, and more specifically event-related potentials (ERP), has been used to delineate real-time neural responses to behavioral tasks after PA interventions (15,16). ERPs refer to patterns of neuroelectric activation that occur in response to, or in preparation for, a stimulus or response. This approach offers the requisite temporal resolution to gain insight into cognitive operations that occur between stimulus engagement and response execution, and it may be more sensitive in parsing the effect of PA on the various aspects of cognition relative to overt task performance measures. However, research using Physical Activity, Brain, and Cognition duction of this article is prohibited. neuroelectric assessment after acute PA interventions, especially in children, was essentially nonexistent until the turn of the millennium. Since then, this field has prospered over recent years, as evidenced by the increasing number of publications focusing on the effects of a single bout of aerobic PA on brain and cognition using neuroelectric and behavioral techniques (see Fig. 1. of Pontifex et al. [16]). Accordingly, the ensuing descriptive review demonstrates the current understanding of the effects of acute PA on childhood brain, cognition, and academic achievement. Acute PA, Brain, and Cognition PA has increasingly been cast aside during children’s school days, as they become more regimented toward preparation for standardized testing and examinations, although such a strategy has shown no improvements in grades and could even be detrimental to health (17). This trend is contradictory to evidence linking PA to academic achievement (18–20). Even short sessions of PA in the classroom can have a positive effect on academic behaviors, such as paying attention and staying on task (21–24). A recent study even showed that improvement in these behaviors can occur with as little as a 4-min “dose” of in-class PA (23). Such findings support the feasibility of implementing PA before learning, which could in turn foster performance in a learning environment. Cognitive function is a candidate mechanistic moderator in the relationship between PA and academic performance. Thus, investigating the transient effects of PA on cognitionmay be the first step in gaining a mechanistic understanding of this framework. Yet, this topic is still building a repertoire. A study byHowie et al. (25) tested preadolescent children (9 to 12 yr old) in a classroom-based acute high-intensity PA intervention, which was delivered in the form of activity breaks that were not integrated with academics, and compared groups that underwent these PA sessions for 5, 10, or 20 min against a control group. Children were tested on a math problem set and cognitive battery after the PA session. The authors found that the 10and 20-min PA groups outperformed the other groups in math, but there were no differences in the trail making test and digit recall performance, cognitive tasks that tap executive control. That is, the PA groups performed better on academic but not cognitive outcomes. This study, in isolation, suggests that acute PA may selectively affect academic but not cognitive performance. However, the lack of an effect of cognitive performance may be due to the cognitive tasks selected for assessment and the manner in which they are administered, whichmay not have the requisite sensitivity to reflect smaller changes in cognition as a result of acute PA. Therefore, testing the subtleties of the transient effects of PA may be better suited for laboratory paradigms. For instance, studies byHillman et al. (26) and Pontifex et al. (27) showed that an acute bout of walking significantly enhanced both academic and executive control performance using computerized paradigms in preadolescent children. The ensuing narrative will further detail the particular effects that acute PA can have on cognitive function, particularly the multidimensional executive control construct, and highlights the value of PA as a valuable tool to aid in children’s education and, in turn, bolster support for increasing opportunity of PA in schools. Acute PA Effects on Executive Control Executive control describes a subset of goal-directed, selfregulatory operations involved in the selection, scheduling, and coordination of computational processes underlying perception, memory, and action. The core cognitive processes collectively termed “executive control” include inhibition, working memory, and cognitive flexibility (28,29). Inhibition (often termed “inhibitory control” or “attentional control”) refers to the ability to override a strong internal or external pull to appropriately act within http://www.acsm-tj.org Copyright © 2019 by the American College of Sports Medicin environmental constraints (28). Workingmemory (sometimes distinguished into the terms “updating” and “working memory capacity”) refers to the ability to hold information in mind and manipulate it. Working memory is also heavily involved in other executive control processes because it relates to the ability to represent internal goals and standards for the comparison of those goals, against current performance, to regulate behavior (28–30). Cognitive flexibility (also known as “mental flexibility” or “set shifting”) is the ability to quickly and flexibly change perspectives, focus attention, and adapt behavior to execute goaldirected actions (28,31). During maturation, executive control exhibits protracted development relative to other cognitive processes (32), with e