Physical Exercise and Cognitive Development: Influence of Training Modalities and Characteristics

Abstract

Physical exercise has been shown to relate to cognitive performance in a diverse range of populations, including children. Evidence has also indicated that the link is at least partly causal, with exercise interventions bringing a myriad of benefits to cognitive development. However, not all types of exercise regimens appear to be created equal—recent findings suggest that although ubiquitous, aerobic exercise might benefit from added components, either in terms of training modalities or cognitive demands. Here, I briefly review evidence for the general impact of physical exercise on cognitive development, before focusing in more detail on recent trends in exercise-induced cognitive enhancement. In particular, I emphasize the importance of exercise intensity, and argue that, given time constraints, aerobic exercise might not always be an optimal way to target the brain. I then discuss the potential for including additional components within exercise regimens, to enable more general, far-ranging, improvements. Finally, I conclude with a number of recommendations to facilitate the translation of research findings into practical situations. TRAINING MODALITIES AND CHARACTERISTICS 2 Introduction In the first decade of life, children are confronted with a number of challenging situations, often in environments they have never encountered before. This wide range of experiences shapes the teenagers they will grow into, in turn influencing the adults they will become. Exercise and sports occupy a central place among these experiences, helping children develop their motor skills, challenging cognitive processes in a unique and sustained way, and ensuring healthy habits are incorporated at a young age (see for example Singh et al., 2019). Given its influence on brain and behaviour, can exercise be leveraged to maximize cognitive development? Recent trends of research across psychology and education have explored how malleable cognition is, and the extent to which individual cognitive abilities can be influenced by short interventions (see for a review Moreau, Macnamara, & Hambrick, 2018). These include a wide variety of interventions, ranging from computerized training (Jaeggi, Karbach, & Strobach, 2017), to videogame training (Green & Bavelier, 2015), mindfulness meditation (Zeidan, Johnson, Diamond, David, & Goolkasian, 2010), or even interacting with nature (Berman, Jonides, & Kaplan, 2008), all of which have been purported to directly influence cognitive function. Yet the best way to exercise the brain arguably remains physical exercise. In the specific context of exercise interventions, researchers have investigated how short-term regimens (Chang, Labban, Gapin, & Etnier, 2012; Moreau & Chou, 2019) and long-term interventions (Northey, Cherbuin, Pumpa, Smee, & Rattray, 2018) affect cognitive abilities. Although some work has started to apply this knowledge to developmental populations (see for a review Tomporowski & Pesce, 2019), the power of exercise remains largely untapped in young populations. In this chapter, I provide a brief review of the literature linking physical exercise and cognition, with a specific focus on cognitive development. I further discuss components of exercise that appear to influence this relation, such as exercise modalities (e.g., intensity, duration, frequency) and activity properties (e.g., novelty, diversity, complexity). Finally, I close with a discussion of practical recommendations, to help practitioners translate scientific findings in a way that can directly impact society. Physical Exercise and Cognition Physical exercise has long known to be associated with a myriad of benefits, including protective effects against a range of conditions including stroke, cancer, and TRAINING MODALITIES AND CHARACTERISTICS 3 cardiovascular diseases (Blair et al., 1995). By the same token, lack of exercise is linked to higher risks for disorders such as autism, schizophrenia, and attention deficit/hyperactivity disorder (ADHD) (Penedo & Dahn, 2005). Yet the impact of physical exercise goes beyond protective effects—it is also associated with better cognitive performance on tasks of working memory (Moreau, 2013), cognitive control (Moreau, Kirk, & Waldie, 2017), executive function (Moreau & Chou, 2019), and spatial ability (Moreau, 2012; Moreau, Mansy-Dannay, & Clerc, 2011). Importantly, the link is (at least partly) causal, a point that has been demonstrated with interventions showing enhanced cognitive performance post-exercise in academic and professional settings (Castelli, Hillman, Buck, & Erwin, 2007; Coe, Pivarnik, Womack, Reeves, & Malina, 2006; Keeley & Fox, 2009; Moreau et al., 2017), better regulation of emotions (Blumenthal et al., 1991), and higher quality of life (Cancela Carral & Ayán Pérez, 2007). At the functional level, work by Chaddock-Heyman and colleagues (2013) has reported decreases in neural activity in the right anterior prefrontal cortex while children were engaged in cognitive control tasks after a one-year exercise intervention. These changes in neural activity were accompanied with cognitive improvements measured at the behavioral level. Note, however, that not all studies find decreases in neural activity associated with exercise interventions; for example, Davis and colleagues (2011) reported increases in prefrontal activity following a 13-week intervention program. These mixed findings suggest that complex factors may be associated with the neural substrates of exercise-induced cognitive improvements, in line with more general findings in the field of neuroscience (e.g., Xu, Calhoun, & Potenza, 2015). Irrespective of the specific neural effects of exercise, however, behavioral improvements post-interventions remain typical (but see Young, Angevaren, Rusted, & Tabet, 2015). At the structural level, physical exercise generally promotes neurogenesis (van Praag, Kempermann, & Gage, 1999; Vivar, Potter, & van Praag, 2013), and enhances a number of other processes such as neuronal survival (Vaynman, Ying, Yin, & Gomez-Pinilla, 2006) and brain vascularization (Colcombe et al., 2006). Structural studies using Diffusion Tensor Imaging (DTI) have shown that physical exercise interventions in populations of children lead to greater white-matter integrity, especially in the uncinate fasciculus (Schaeffer et al., 2014) and the superior longitudinal fasciculus (Krafft et al., 2014), two fundamental networks connecting the limbic system and the prefrontal cortex, and the temporal and parietal lobes, TRAINING MODALITIES AND CHARACTERISTICS 4 respectively. These findings are corroborated by observational evidence, for example showing white-matter integrity differences between children of various fitness levels (Chaddock-Heyman et al., 2014). Exercise also upregulates neurotransmitter concentrations, as well as key mediator of the relation between exercise and cognition such a brain-derived neurotrophic factor (BDNF), which concentration increases in specific parts of the brain such as the hippocampus post-exercise (Neeper, Gómez-Pinilla, Choi, & Cotman, 1996). This post-exercise increase appears within minutes and can last several weeks (Berchtold, Patrick Kesslak, Pike, Adlard, & Cotman, 2001). Interestingly, higher BDNF concentrations are especially pronounced in specific regions of the brain such as the hippocampus, the caudal neocortex and the dentate gyrus—areas that are not primarily involved in motor control but in general cognitive function (Neeper et al., 1996). This finding supports the notion that physical exercise has a broad impact on the brain, above and beyond sensorimotor areas, and including brain regions involved in complex cognition. Overall, the aforementioned literature reports potent effects of exercise on the brain. Yet, this line of work almost exclusively focuses on aerobic exercise, a specific type of moderate-intensity, sustained regimens that is popular but possibly not representative of typical exercise, especially in younger populations. Historically, this has followed on from animal research that focused on forms of exercise resembling human aerobic effort (e.g., Fuchs & Gould, 2000; van Praag et al., 1999). However, recent work has shown that alternatives have great potential. In the following section, we describe work that has used regimens that may be more ecological, and thus might better translate to practical implementations. Critical Components of Exercise Beyond the general trend linking physical exercise to brain function and cognition, other research has further explored how varying components of exercise affects its impact on brain and mind. These components can be divided into two broad categories: the training modalities of exercise, such as intensity, duration and frequency, and the characteristics of the activity relative to each individual, for example, its novelty, diversity, or complexity. Although early work on the link between brain and exercise has focused on aerobic exercise, novel trends have since emerged. For example, recent work in our group has shown that interventions involving high-intensity training—short bursts of exercise, repeated a number of times and interleaved with rest—could allow substantial improvements, TRAINING MODALITIES AND CHARACTERISTICS 5 comparable to those of longer, less intense regimens (Moreau & Chou, 2019; Moreau et al., 2017). In a six-week randomized controlled intervention, we found that high-intensity training elicited improvements in cognitive control and working memory constructs assessed via a multitude of tasks (Moreau et al., 2017). These findings are consistent with literature showing the clear physiological effect of high-intensity training regimens (Rognmo, Hetland, Helgerud, Hoff, & Slørdahl, 2004) and the health benefits associated with this type of regimen (Costigan, Eather, Plotnikoff, Taaffe, & Lubans, 2015). Further work in our group demonstrated that the acute effects elicited by e