The Effects Of Exercise On Cognitive Function, Academic Performance And Wellbeing In Adolescent Schoolboys

BSE207 Exercise Physiology

Adolescence an opportune phase for cognitive enhancement

Definition of adolescence and puberty

Adolescence is the transition state that exists in between childhood and adulthood. This transition mainly occurs during the age bracket of 10 to 19 years and is mainly defined as series of psychological and physiological changes in the body and mind of the individuals [1]. The physiological change occurring during adolescence is known as puberty and it mainly helps to attain sexual maturity. This physical transition or changes over any particular individual occurring during puberty is mainly visible between 9 to 12 years. Thus alternatively, puberty is regarded as the major life transition from non-reproductive juvenile stage to reproductively competent adult stage [2]. Adolescence stage is extremely significant in every person’s life as it is in this stage that the brain releases some special hormones that promote both physical and cognitive development. Puberty and adolescence, the developmental period associated with puberty is regarded as great physiological, psychological and cultural changes. This is because, puberty and adolescence is associated with great developmental plasticity [1].

Recent advancement in the field of imaging technology has lead to the elucidation the significant amount of brain development is associated during puberty and thus this stage is treated as a special period in one’s life [3]. Puberty is characterised via physical, hormonal and psychological transformation. Under this transformation, human brain undergoes potential changes between the childhood and adulthood. The longitudinal sample analysis study over 275 individuals (7 to 20 years), done via magnetic resonance imaging showed significant changes in the sub-cortical region of human brain during puberty. Further studies in this domain revealed that the pubertal development is extensively associated with the change in the structural volume of different parts of the brain in both the sexes. The main regions of the brain which experience noticeable change during puberty include amygdale, corpus striatum, hippocampus, nucleus accumbes (NA), globus pallidus (GP) and putamen [4]. The imaging technique also revealed a striking change in the white and grey matter of brain between 11 to 25 years of age along with increase in the connectivity between different regions of brain along with the increase in the activity of the dopaminergic neurons in the pre-frontal cortex of the brain. During puberty, there also occurs increase in the linkage between the striatum and limbic system. These plausible changes in the anatomy and physiology of the brain lead to change in the cognitive and behavioural characteristic of an adolescent [3]. This drastic change in the anatomy of physiology of the brain occurring during the puberty lead to significant change in the overall behavioural attitude of an individual in comparison to that his or her childhood and thereby making him or her more prompt in responding to questions [5]. This change in the cognitive thought process among the adolescent due to change in the brain development increases the risk taking attitudes. The subsequent hormonal changes occurring during puberty further exacerbates the overall brain development and change in the neurological signalling [5].  

Importance of physical activity across the lifespan and why is particularly impactful during adolescence

Brain development during puberty

Benefits of active lifestyle are not only restricted to physical health. Higher level of physical exercise is associated with higher levels of cognitive performance among both the younger adults and older adults. Cognitive functions are the special functions that are sub-served via the interplay of the central nervous [6]. Evidence suggest that there exist a causal relationship with the physical exercise and improved interplay between the different signalling pathways of the central nervous system and thereby leading to improved cognitive development [6]. Mild to moderate physical activity like walking has been found to increase the memory and attention among the older adults [7]. Increase in the rate of physical activity during adolescence increase the rate of mean cerebral blood flow into the brain this in turn help in the development of cognitive functioning. Not only this, increase in the overall physical activity among the individuals who are in their pubertal stage helps to increase the lactate threshold. This in turn causes an immediate increase in the plasma concentration of adrenocorticitropic hormone, carecholamines, beta- endorphin and vasopressin in the peripheral blood circulation which is thought to increase the secretion of neurotransmitter secretion in the central nervous system causing elevated arousal and thus enhancing the overall cognitive performance [6]. Additionally numerous neurotrophic factors like nerve growth factor, brain-derived neurotrophic factor etc is found to get unregulated during physical activity. These elevated levels of neurotrophic factors plays a crucial role in the neural growth and neuron survival and thus influencing learning and overall memory processes which are important for the cognitive functioning [6]. Physical activity also leads to high physical fitness this in turn leads to higher cardiovascular fitness, larger volumes of basal ganglia and hippocampus among the children who are in their adolescence. All these cumulate into increase level of cognitive performance, memory development and thereby leading to well-developed executive functions for day-to-day functioning [7].

International public health and health promotion organizations have highlighted that the health risks across the lifespan are mainly associated with the decrease in physical activity. The globally physical inactivity is found to increase the susceptibility of the development of type 2 diabetes, breast cancer, colon cancer, rectal cancer and risk of coronary heart disease [8]. This lack of physical activity and its relation to the development of the coronary heart disease is also prominent among the children who are in their adolescence. However, in spite of the known relation between the lack of physical activity and the subsequent threat of the physical and the mental health, there is lack of proper awareness of physical activity in schools. However, the practising physical activity depends on several determinants like physiological, sociocultural, psychological and ecological. For example, in schools it has been found that the girls are less active than boys in the domain of physical activity and the older children and adolescents are comparatively less active than the younger children [8]. Another systematic review further highlighted that during the past 30 to 40 years the overall rate of physical activity in schools around the word has decreases gradually. Given that the significant proportion of the total waking hours spent within the school premises and in performing associated school activities, very less is known about the physical activity of the students during their school hours and during the school-related after school activities. In spite of having excellent research and prominent public health surveillance systems, the present monitoring of the school-related physical activities among the adolescence is inadequate [9]. Another research however, helped to throw light over the current trends in the physical activities in schools. It showed that the majority of youth worldwide now fail to meet the established physical activity standards. Increase in the class duration and lack of proper game classes lead to increase in the sedentary behaviour among the children. The sports are held annually and not on quarterly or semi-quarterly basis leading to the decrease in interest in the overall physical activity or sports [10].

Physical activity, heath benefits and cognitive development

Exercise induced cognitive development demands both acute and chronic exercise as evident from the research conducted over both human and animal models. Acute exercise is defined as single bout exercise and chronic exercise is characterised by repetitions of bouts of exercise over time which lasts from weeks to years [11].  

Table 1: Taxonomy of physical exercise
Type of effect	Mode of exercise	Type of physiological change	Type of brain mechanism underpinning the effect
Acute	Single bout of exercise	Transient	Modulation of the activity of a neural network
Chronic	Regular exercise	Durable	Patho-anatomical changes in the brain structure

Single session of exercise helps to increase the cognitive performance via the increase in the overall flow of blood within the body along with the increase in release of the neurotransmitter [11]. A meta-analysis conducted by Chang et al. (2012) highlighted that the acute exercise do not have significant effect over the overall improvement of the cognitive function of an individual but is effects on the cognitive ability is slightly greater than zero. The range of cognitive benefits mainly depends on a number of factors that is duration of the exercise and intensity of the exercise however, the improvement of the cognitive function is more prominent among the individuals who are physically fit. Effects of the acute physical exercise over the cognitive development during adolescence are mainly attributed by the release of the brain-derived neurotrophic factor (BDNF). However, the effect of improve in cognition is more pronounced in males in comparison to that of females and this is because, decrease in the level of secretion of BDNF among the females [12]. In relation to BDNF, it can further be stated that the increase in the level of the physical activity via execution of the acute physical exercise leads to increase in the level of secretion o BDNF in the peripheral levels and increase in the intensity of the physical exercise help to increase in the secretion of BDNF and thereby promoting modulation in the overall cognitive development [13].

Chronic exercise leads to the increase in secretion of the PGC-1a which in turn leads to the activation of the FNDC5 pathway and thereby promoting the secretion of brain-derived neurotrophic factor (BDNF) from the hippocampus of the brain and thereby facilitating the overall development of the cognitive function [14]. FNDC5 pathway mainly leads to the generation of elevated levels of irisin and this in turn induces the transcription of the BDNF gene and other neuroprotective gene and thereby leading to the increase in the development of cognition [14]. Chronic exercise pathway mainly encompasses endurance exercise which is not only beneficial for the brain health and cognitive function but also promotes physical health and well-being. The chronic exercise pathway is also reported to decrease the mental health complications like depression [15]. Chronic physical exercise leads to the increase in the rate of secretion of neuronal nitric oxide synthase (nNOS). The secretion of nNOS leads to the promotion of angiogenesis in the human skeletal muscle. This increase in the rate of angiogenesis after the endurance exercise in the human skeletal muscles leads to increase in the overall blood circulation. The same has been proved by the comparative biopsies conducted over the vastus lateralis (VL) muscle from 10 sedentary males and 10 males who are under mild to moderate chronic exercise training. The increase in the overall blood circulation increases the overall level of neurotransmission and thereby facilitating overall cognitive development [16]. Chronic physical exercise pathway also promotes neuro-synaptic genesis which in turn again facilitates better transmission of the neuronal impulses and thereby helping the population who are in their adolescences who improve on their cognitive functions [17].

Present trend of decrease in physical activity in school: review

The study conducted over 30 adolescent between the age group of 13 to 14 years highlighted that the level of cognitive development depends on a perfect amalgamation of the level of physical fitness and aerobic exercise. Such that individuals who are more physically fit are more likely to observe the beneficial effects on cognitive development in comparison to that of the individual who are physically unfit or leads a sedentary life style. A bout of acute exercise followed by a period of relaxation helps to increase behavioural differences. However, fit groups of individuals revealed more interaction between the fitness level and acute physical exercise in comparison to the unfit individuals [18]. Such that it is recommended that the individuals who are unfit are required to perform the exercise in more cyclic bouts in order to visualize promising outcomes in the cognitive development. Increase in the overall cognitive development can then be visualised by the increase in the overall attention level or the academic performance [19].

The benefits of physical exercise over the cognitive development of an individual or children during their adolescence is mainly depends on their level of physical fitness, the intensity and the duration of the physical exercise undertaken. Mainly chronic physical exercise accompanied with aerobics is found to provide useful results in the level of cognitive development. Moreover, the observance of the level of the cognitive development between the adolescents arising out of the physical exercise also varies from person to person and the main reason behind this is the difference in the level of neuronal plasticity among the individuals [20].  In order to sustain the level of cognitive development, the physical activity must be continued throughout the life. For example, it has been found that the individuals who are more physically active during their childhood suffers from memory loss during the adult stages of the life. Increase in mild to moderate physical activity coming in the form of walking helps to fight against memory loss [21].

The impact of exercise is not similar across the lifespan of the individuals. The research highlighted that that increase the effect of physical exercise on the overall cognitive development is maximum during the adolescent stage as it is in this stage that the significant brain and the neuronal development occurs [22]. As a person ages with time, there occurs degeneration in the overall neuronal signalling leading to decrease in the effect of exercise over all overall cognitive function. However, the research has indicated that the physical exercise during the young adult age promotes healthy cognitive ageing and thus helping to get the useful cognitive results from the physical activity. On the other hand it can also be said that with age there occurs increase in the level of obesity among the individuals and this increase in the level of obesity leads to decrease in the overall impact of the physical exercise over the cognitive function [23].  

Cognitive functions refer to the high order mental process that facilitate the procedure of gathering and processing information. In other words, cognitive function have been defined as cerebral activities that have the potential of leading to knowledge and includes several mechanisms of information acquiring. Cognitive functions most commonly encompass memory, reasoning, language, attention and directly result in attainment of knowledge and information [24]. Thus, it is an intellectual process that helps an individual gain an awareness of or perceive and comprehend a range of ideas. The word cognition dates back to the 15^th century when it was used to describe awareness and thinking [25]. The theory of introspection was elaborated by Wundt, who defined it as an examination of the inner feelings of a person [26]. Modern neuroscientists and psychologists found his statements as subjective and chose to bank on objective methods to conclude about human cognitive functions.

Mechanisms of exercise-induced cognitive enhancement

Several inferences were drawn by behavioural psychologists regarding the response of the brain to some stimuli. These information were collected by observing the changes in brain structure and functioning, while a person grew and acquired new skills. Furthermore, neuroscientists also conducted research to gain a deeper understanding of the executive functions of the brain by conducting comparative studies between brain anatomy and human behaviour, with the help of fMRI techniques, which illustrated electrochemical differences in the brain [27].

Top-down and bottom-up processes refer to different strategies of knowledge ordering and information processing that are used in a range of fields that include scientific, humanistic and software theories. Sensory input is typically considered bottom-up and the higher cognitive functions that gather more information from a range of sources are referred to as top-down [28]. Bottom-up approach is primarily characterized by characterized by the absence of high level directions in areas pertaining to sensory processing. This process includes stimulus evaluation and encoding [29]. On the other hand, a top-down process is characterized by high direction levels of sensory processing, such as targets and goals. In other words, strategy use, planning and goal directed organisation are some major attributes of the top-down process [30].

Executive function is an umbrella term that generally encompasses the necessary cognitive skills that help in conduction a goal directed, purposeful activity. It refers to the cognitive domains comprising of high level decision making and thinking [31]. It can be divided into a range of subdomains that are characterized by mental flexibility, planning, response inhibition and strategy.

Attention refers to the process of taking possession with the help of the mind in a vivid and clear form, out of several train of thoughts. Thus, attention implies the withdrawal from certain things, with the aim of effectively dealing with others [32]. Attention, is also mentioned as enthrallment, and is often defined as the cognitive and behavioral process of placing selective concentration on certain discrete aspects of information, regardless of their objective or subjective status, while ignoring all other perceivable information.

Working memory is comprised of major brain processes that are responsible for information storage and retrieval in a temporary manner. Working memory allows focusing on attention, resisting distractions and also guides the decision making processes. Thus, this cognitive system is associated with limited capacities that are responsible for the temporary holding of information, and is imperative for reasoning and behaviour [33]. It is both a memory ability and an attentional function.

Learning refers to the process or activity of gaining skills or knowledge by practicing, studying, getting taught and experiencing events. Thus, learning involves the process that helps an individual to acquire new, existing or modifying information, knowledge, skills, behaviour, and values [34]. Learning most often occurs consciously or subconsciously and is a form of an aversive event which cannot be escaped or avoided.

Cognitive Assessment Battery (CAB) refer to a professional tool that facilitates the study of the brain functions of children and adults, in depth, with the use of several cognitive tasks. Conduction of such tests help in determining the performance of individuals on cognitive tasks that is imperative for the diagnosis of a plethora of cognitive disorders such as, dementia, Alzheimer’s disease and mild cognitive impairments. Such CAB are also essential for defining the patterns and magnitude of changes in cognition, frequently associated with normal aging of an individual [35]. The assessments also facilitate the process of bringing about clear distinctions between normal and clinically abnormal cognitive changes.

The ‘gold standard’ followed for assessment of cognitive functioning encompasses a face-to-face administration of the CAB, comprised of a series of standardized cognitive tests that measure the primary cognitive abilities such as, learning, attention, visuo-spatial abilities, language, memory, and other higher executive functions [36]. Neuropsychological evaluations are found to consist of numerous measures of affect and mood, in addition to relevant information that pertain to the well-being and quality of life of the person.

Cognitive reappraisal involves the process of rethinking about the meanings of events or affectively charged stimuli in certain terms that have the potential to alter the emotional impacts. Reappraisal also appears to be largely dependent on interactions between the cingulate and prefrontal regions of the brain that are associated with the insula and the amygdala, responsible for emotional responding [37]. Changes in autonomic responding and emotional experience are also correlated with concomitant fall and rise of the prefrontal cortex and amygdala. Subjective wellbeing is often expressed in terms of the quality of life of the individuals and their self-evaluation [38]. Theories about the subjective wellbeing suggest that it is common for individuals to feel good about themselves. The SWB theory states that several stabilising forces namely positive affectivity, adaptation, and cognitive buffers maintain the subjective wellbeing of a person [39]. 

These buffer variables commonly encompass cognitive and positive biases related to feelings of self-worth and self-esteem, optimism and perceived control [40].  Interaction of these buffers with the environmental experiences result in maintenance of the wellbeing at a steady level. Conditions that involve negative influence exceeding the capacity of homeostasis results in a rise or drop in the wellbeing, beyond the pre-determined range. Self-regulation covers the capacity to act in a way that is capable of considering the long term significances, in places of transient feelings. Emotional self-regulation is the ability that helps people to respond appropriately to the ongoing experiences with a plethora of emotions in a socially tolerable and flexible manner. Thus, this attribute enables people to control and monitor their behaviour, thoughts, emotions and alter them in accordance to the demands of the current situation.

Recent meta-analytic studies suggested for the high prevalence of depressive symptoms among children and adolescents, aged 9-16 years [41]. Most commonly known a teenage depression, this emotional disorder occurs due to the developmental and social challenges that are faced by the adolescents. Depression in adolescents has been identified as a risk factor for suicidal ideations and more than half of the victims have been found to report major depressive disorder during their death [42]. Studies have provided evidence for the fact that rates of depression substantially increase during adolescence [43]. Lower FN amplitudes have also been associated with increased depression, even on controlling the symptoms and neuroticism at baseline [44]. Prevalence of postpartum depression was also observed among adolescent mothers in another randomized controlled trial [45].

Depression has also been associated with distortions of body image among adolescent boys. Boys who were of average weight were found to view themselves as underweight or weight distorted. Furthermore, overweight boys were also found to reported significant high levels of depression [46]. Rumination has also been found resoonsible for decreasing the executive capacity of adolescents and leads to their poor performance in cognitive tests [47]. A range of biological and physiological processes occur during the transition from adolescence to adulthood. Moreover, depressive symptoms are also linked to increased risks of psychosocial morbidity in adulthood [48].

Fluid intelligence is defined as the capability of solving new problems, using logic in different situations and identifying new patterns. This form of intelligence is found to peak in the early stages of life and involves the capacity to identify relationships as well, which in turn underpin novel problems, in addition to extrapolating the findings with the use of logic [49]. On the other hand, crystallised intelligence consists of the ability of using experiences and learned knowledge. Several studies have proposed that fluid intelligence is an essential component of academic performance due to the fact that the former is closely associated with general intelligence [50]. This plays a central role in studies and academics, as suggested by position effect. Two principle components of fluid intelligence have been associated with verbal and mathematical performance [51].

Extremely intelligent individuals are more efficient in learning skills in complex and novel situations that results in an increased potential in achieving academic success. This has also been established by previous findings that determined existence of a positive relationship between the rates of learning, fluid intelligence and learning in real scenarios [52]. Thus, the ability of an individual to learn in new situations is the fundamental facet of fluid intelligence. Several factors create an impact on cognitive function in academics, thereby determining the school grads, and other attitudes specific to the academic domain namely, grit, motivation, metcognition, classroom practice, behaviour, and curriculum [53]. In other words, school learning is a complex set of interactions between the distal and proximal environmentl characteristics of a student [54].

This cognitive mode of training makes complete use of mental exercises that work and target the core cognitive skills of the brain. The skills that are addressed in such training sessions encompass long and short term memory, attention, processing speed, auditory processing, reasoning and logic [55]. The Hebbian learning theory proposed an explanation for neuron adaption in the brain that occurs during the learning process. The theory provided a description for the mechanism of synaptic plasticity that elaborated on the fact that an elevation in the synaptic efficiency is a direct result of the persistent and repeated stimulation of the presynaptic cells [56]. Thus, repeatedly performing some cognitive tasks makes the associated brain areas form stronger associations [57].

Hence, interventions that focus on cognitive training could play a significant role in improving the cognitive abilities by modifying brain activations. Brain training tasks have been recognised to play an integral role in bringing about improvements in the processing speed and executive functions of the elderly. Thus, short term training is directly responsible for improving higher executive functions [58]. Use of video gaming has been found crucial for improving the perceptual and cognitive abilities of people [59]. Moreover, studies have also established the effectiveness of these training activities on neural plasticity [60]. However, one major drawback is related to the fact that although the training improves performance, the effects are particularly restricted to the specific tasks performed [61].

Working memory training is conducted with the aim of improving the working memory of a person. This working memory pertains to an important intellectual faculty that is linked to ageing, IQ and mental health.  Evidences claim that WM training programs not only effective for the treatment of ADHD and other cognitive disorders, but also for enhancement of intelligence and cognitive functioning in developing children and adolescents [62]. WM has shown significant associations with reasoning, decision making and problem solving capabilities [63]. Furthermore, it is also imperative for the acquisition of skills and knowledge, thereby improving the academic success and educational attainment. A range of programs have been designed, based on WM training such as, Jungle Memory Program and Cogmed WM Training [64]. However, despite the huge success of WM training on transfer effects, the underlying neural mechanism remains undefined [65].

Cognitive maturation in adolescence generally encompasses a range of expanded capabilities falling within the category of executive functions. This maturation embraces the transition from a concrete thinking to abstract forms, better peer interactions, increased ability in drawing logical conclusions, and renewed abilities of self-regulation and evaluation [66].  These directly enhance the capacity of adolescent to formulate hypothesis, express features of altruism, design idealistic situations and develop dreams for a good future.

The primary cognitive change is the shift from concrete operational thinking to abstract thinking. Piaget suggested that this evolution occurs in the form of an adaptation to external stimuli, demanding production of hypothetical responses from an adolescent [67]. MRI studies have also shown evidences of preadolescent increase in the gray matter, which have been attributed to increase in synapses, due to enhanced ability of the adolescents in abstract thinking [68].

The human brain has the capability of adapting to the altering demands by bringing about a change in the structural and functional properties, commonly referred to as neuroplasticity, which in turn results in the process of acquiring and learning new skills. Convergent evidences from both animal and human studies suggests that performing physical activity has the potential to enhance neuroplasticity of specific brain structures, thereby improving cognitive functions [69]. Animal studies have also been conducted that have successfully identified enhancement of synaptogenesis, neurogenesis, and angiogenesis, along with the concomitant release of neurotrophins [70]. These major neural mechanisms have been correlated with the mediation of cognitive effects related to physical exercise. Physical exercises also triggers processes facilitating neuroplasticity, thereby enhancing the capacity of an individual to respond to newer behavioural adaptation demands [71]. The association of long-term dance experiences were tested with respect to volume of gray matter and cognitive performance among women aged more 65-82 years. No significant differences were found in the four cognitive domains, thereby suggesting that moderate dance failed to induce any effects on cognitive functioning and volume of gray matter, when a certain level was reached.

Reductions were observed in improvements of procedural memory that were induced by exercise in another study [72]. This was associated with a simultaneous increase in its temporal proximity from acquisition. Thus, the timing of exercise was considered as an essential factor for consolidation of motor memory. Findings from another study suggested that impairment in motor performance while performing dual-task walking was mirrored in the form of neural activation patterns [73]. Regular exercise has the capability of delaying brain shrinkage, by dramatically increasing brain activity. An increase in the brain’s blood flow brought about by physical exercise, triggers a series of biochemical changes that enhance neuroplasticity and produce newer connections. Furthermore, participation in aerobic exercise for 15-30 minutes also exerts positive impacts on the brain such as, improved executive function and memory [74].

Health experts are often found to remark that availability of exercise in the form of pills would make it the most sought after drug in the pharmaceutical industry. Decades of research have identified exercise as an essential tool that enhances a range of physical indices such as, bone density, balance, lipid profile, cardiovascular health, and blood pressure [75]. It has been well established that BDNF, the brain-derived neurotrophic factor gets released during aerobic exercise and stimulate the growth of new neurons [76]. Aerobic fitness has been identified to revert loss of brain tissue due to aging, thereby enhancing the functional aspects of brain regions that are involved in cognition. More active individuals have the capability of allocating increased attentional resources towards the environment and also process information rapidly. New evidences indicate that exercise affects numerous molecular events, allied with synaptic plasticity [77]. Modulation of molecular systems related with energy is a pivotal mechanism that governs the influence of exercise on cognition.

Findings from a study correlated higher fitness with greater bilateral hippocampal volume, and improved spatial memory performance [78]. Increase in the hippocampal volume by 2% was also found among participants in exercise treatment group in another study, thereby indicating the positive effects of exercise on cognition [79]. Evidence also suggest that volumetric differences in important brain regions have been recognised responsible for mediating differences in cognitive performance, such as task switching [80]. MRI findings also establish the link between exercise and an upregulation of the cerebral blood volume, present in the dentate gyrus, the regions that is responsible for adult neurogenesis [81].  Thus, it can be well established that exercise creates a major influence on the molecular substrates in control of cognition.

The primary aim of the research is to investigate the effects of exercise on the cognitive function and academic performance of adolescent school children.

• H₁– Exercise will improve the cognitive function and academic performance of adolescent school children.
• H₀– Exercise will fail to create any impact on the cognitive function and academic performance of adolescent school children.

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