Let's look at the relationship between potential energy and stability. A system's stability is a measure of its tendency to change. A more stable system is less likely. More recently, reviews have attempted to describe the effects of an acute or single bout of Positive relationships among physical activity, physical fitness, and .. 75 minutes of PAAC lessons per week, BMI remained stable (see Figure ). Attractive forces lower the potential energy of the molecule and repulsive forces the most stable interaction between a substrate/ligand/drug and the enzyme.
Rather, developmental stage is a significant determinant of motor skills, physical capacity, and the adaptation to activity that is reasonable to expect see Box Growth is the normal process of increase in size as a result of accretion of tissues characteristic of the organism; growth is the dominant biological activity for most of the first two decades of life.
Developmental Stages Postnatal growth is commonly divided into three or four age periods. Infancy spans the first year of life. Childhood extends from the end of infancy to the start of adolescence and is often divided into early childhood, which includes the preschool years, and middle childhood, which includes the elementary school years, into the 5th or 6th grade.
Adolescence is more difficult to define because of variation in its onset and termination, although it is commonly defined as between 10 and 18 years of age WHO, The rapid growth and development of infancy continue during early childhood, although at a decelerating rate, whereas middle childhood is a period of slower, steady growth and maturation.
Differences between boys and girls are relatively small until adolescence, which is marked by accelerated growth and attainment of sexual maturity Tanner, For example, the head accounts for 25 percent of recumbent length in an infant and only 15 percent of adult height, while the legs account for 38 percent of recumbent length at birth and 50 percent of adult height. These changes in body proportions occur because body parts grow at different rates.
From birth to adulthood, as the head doubles in size, the trunk triples in length, and arm and leg lengths quadruple. Coincident with these changes in body proportions, and in part because of them, the capacity to perform various motor tasks develops in a predictable fashion. For example, running speed increases are consistent with the increase in leg length. Neurological development also determines skill progression.
Young children, for example, when thrown a ball, catch it within the midline of the body and do not attempt to catch it outside the midline or to either side of the body. As proximodistal development proceeds, children are better able to perform tasks outside their midline, and by adolescence they are able to maneuver their bodies in a coordinated way to catch objects outside the midline with little effort.
Physically active and inactive children progress through identical stages. Providing opportunities for young children to be physically active is important not to affect the stages but to ensure adequate opportunity for skill development. Sound physical education curricula are based on an understanding of growth patterns and developmental stages and are critical to provide appropriate movement experiences that promote motor skill development Clark, The mastery of fundamental motor skills is strongly related to physical activity in children and adolescents Lubans et al.
Mastering fundamental motor skills also is critical to fostering physical activity because these skills serve as the foundation for more advanced and sport-specific movement Clark and Metcalfe, ; Hands et al. Physical activity programs, such as physical education, should be based on developmentally appropriate motor activities to foster self-efficacy and enjoyment and encourage ongoing participation in physical activity.
Biological Maturation Maturation is the process of attaining the fully adult state.
In growth studies, maturity is typically assessed as skeletal, somatic, or sexual. The same hormones regulate skeletal, somatic, and sexual maturation during adolescence, so it is reasonable to expect the effect of physical activity on these indicators of maturity to be similar.
Skeletal maturity is typically assessed from radiographs of the bones in the hand and wrist; it is not influenced by habitual physical activity. Similarly, age at peak height velocity the most rapid change in heightan indicator of somatic maturity, is not affected by physical activity, nor is the magnitude of peak height velocity, which is well within the usual range in both active and inactive youth.
Discussions of the effects of physical activity on sexual maturation more often focus on females than males and, in particular, on age at menarche first menses. While some data suggest an association between later menarche and habitual physical activity Merzenich et al.
While menarche occurs later in females who participate in some sports, the available data do not support a causal relationship between habitual physical activity and later menarche. Puberty is the developmental period that represents the beginning of sexual maturation.
It is marked by the appearance of secondary sex characteristics and their underlying hormonal changes, with accompanying sex differences in linear growth and body mass and composition. Recent research suggests that the onset of puberty is occurring earlier in girls today compared with the previous generation, and there is speculation that increased adiposity may be a cause Bau et al.
Conversely, some data suggest that excess adiposity in boys contributes to delayed sexual maturation Lee et al. Pubescence, the earliest period of adolescence, generally occurs about 2 years in advance of sexual maturity. Typically, individuals are in the secondary school years during this period, which is a time of decline in habitual physical activity, especially in girls.
Physical activity trends are influenced by the development of secondary sex characteristics and other physical changes that occur during the adolescent growth spurt, as well as by societal and cultural factors.
Research suggests that physical inactivity during adolescence carries over into adulthood Malina, ab ; CDC, It is critical that adolescents be offered appropriate physical activity programs that take into account the physical and sociocultural changes they are experiencing so they will be inspired to engage in physical activity for a lifetime.
What is the relationship between potential energy and stability?
As discussed below, adequate physical activity during puberty may be especially important for optimal bone development and prevention of excess adiposity, as puberty is a critical developmental period for both the skeleton and the adipose organ.
Adolescence is the transitional period between childhood and adulthood. The adolescent growth spurt, roughly 3 years of rapid growth, occurs early in this period. An accelerated increase in stature is a hallmark, with about 20 percent of adult stature being attained during this period. Along with the rapid increase in height, other changes in body proportions occur that have important implications for sports and other types of activities offered in physical education and physical activity programs.
As boys and girls advance through puberty, for example, biacromial breadth shoulder width increases more in boys than in girls, while increases in bicristal breadth hip width are quite similar. Consequently, hip-shoulder width ratio, which is similar in boys and girls during childhood, decreases in adolescent boys while remaining relatively constant in girls Malina et al. Ratios among leg length, trunk length, and stature also change during this period.
Prior to adolescence, boys have longer trunks and shorter legs than girls Haubenstricker and Sapp, In contrast, adolescent and adult females have shorter legs for the same height than males of equal stature. Body proportions, particularly skeletal dimensions, are unlikely to be influenced by physical activity; rather, body proportions influence performance success, fitness evaluation, and the types of activities in which a person may wish to engage.
For example, there is evidence that leg length influences upright balance and speed Haubenstricker and Sapp, Individuals who have shorter legs and broader pelvises are better at balancing tasks than those with longer legs and narrower pelvises, and longer legs are associated with faster running times Dintiman et al. Also, longer arms and wider shoulders are advantageous in throwing tasks Haubenstricker and Sapp,as well as in other activities in which the arms are used as levers.
According to Haubenstricker and Sappapproximately 25 percent of engagement in movement-related activities can be attributed to body size and structure.
Motor Development Motor development depends on the interaction of experience e. Early movements, critical for an infant's survival, are reflexive and dominated by biology, although environment contributes and helps shape reflexes.
This initial reflexive period is followed quickly by the preadapted period, which begins when an infant's movement behaviors are no longer reflexive and ends when the infant begins to apply basic movement skills e. The period of fundamental motor patterns occurs approximately between the ages of 1 and 7 years, when children begin to acquire basic fundamental movement skills e.
Practice and instruction are key to learning these skills, and a great deal of time in elementary school physical education is devoted to exploration of movement. Around age 7, during the so-called context-specific period of motor development, children begin to refine basic motor skills and combine them into more specific movement patterns, ultimately reaching what has been called skillfulness.
Compensation, the final period of motor development, occurs at varying points across the life span when, as a result of aging, disease, injury, or other changes, it becomes necessary to modify movement. A full movement repertoire is needed to engage in physical activities within and outside of the school setting. Thus, beyond contributing to levels of physical activity, physical education programs should aim to teach basic fundamental motor skills and their application to games, sports, and other physical activities, especially during the elementary years i.
At the same time, it is important to be mindful of the wide interindividual variation in the rate at which children develop motor skills, which is determined by their biological makeup, their rate of physical maturation, the extent and quality of their movement experiences, and their family and community environment.
An increasing amount of evidence suggests that people who feel competent in performing physical skills remain more active throughout their lives Lubans et al. Conversely, those who are less skilled may be hesitant to display what they perceive as a shortcoming and so may opt out of activities requiring higher levels of motor competence Stodden et al.
Children who are less physically skillful tend to be less active than their skillful counterparts Wrotniak et al.
Fundamental skills are the building blocks of more complex actions that are completed in sports, physical activities, and exercise settings. For example, throwing is a fundamental skill that is incorporated into the context-specific throw used in activities such as handball, softball, and water polo.
Fundamental skills are of primary interest to both physical education teachers and coaches, and physical education classes should be designed to challenge learners to develop their motor skills.
The workshop convened 21 experts from a wide range of academic disciplines. One recommendation resulting from the proceedings was for future research to describe the temporal relationship between motor development and physical activity Fulton et al.
The assumption of this relationship is implied in multiple models of motor development Seefeldt, ; Clark and Metcalfe, ; Stodden et al. Two models that are commonly used to examine this relationship are Seefeldt's hierarchical order of motor skills development and the dynamic association model of Stodden and colleagues Seefeldt proposed a hierarchical order of motor skills development that includes four levels: With improved transitional motor skills, children are able to master complex motor skills e.
At the end of this developmental period, children's vision is fully mature. The progression through each level occurs through developmental stages as a combined result of growth, maturation, and experience.
If children are able to achieve a level of competence above the proficiency barrier, they are more likely to continue to engage in physical activity throughout the life span that requires the use of fundamental motor skills.
Conversely, less skilled children who do not exceed the proficiency barrier will be less likely to continue to engage in physical activity. For example, to engage successfully in a game of handball, baseball, cricket, or basketball at any age, it is important to reach a minimum level of competence in running, throwing, catching, and striking. A thorough understanding of how this relationship changes across developmental stages is crucial for curriculum development and delivery and teaching practices.
Lubans and colleagues recently examined the relationship between motor competence and health outcomes. They reviewed 21 studies identifying relationships between fundamental motor skills and self-worth, perceived physical competence, muscular and cardiorespiratory fitness, weight status, flexibility, physical activity, and sedentary behavior.
Overall, the studies found a positive association between fundamental motor skills and physical activity in children and adolescents, as well as a positive relationship between fundamental motor skills and cardiorespiratory fitness.
Other research findings support the hypothesis that the most physically active preschool-age Fisher et al. Rather, the hypothesis suggests that physical activity is influenced when a certain level of motor competence is not achieved and acknowledges that below the proficiency barrier, there is bound to be substantial variation in children's motor competence and participation in physical activity.
The proficiency barrier is located between the fundamental and transitional motor skills periods. The transition between these two levels of motor competence is expected to occur between the early and middle childhood years. Stodden and colleagues suggest that the relationship between motor competence and physical activity is dynamic and changes across time.
The relationship between skills and physical activity is considered reciprocal. It is expected that as motor skills competence increases, physical activity participation also increases and that the increased participation feeds back into motor skills competence.
The reciprocal relationship between motor skills competence and physical activity is weak during the early childhood years ages because of a variety of factors, including environmental conditions, parental influences, and previous experience in physical education programs Stodden et al.
Also, children at this age are less able to distinguish accurately between perceived physical competence and actual motor skills competence Harter and Pike, ; Goodway and Rudisill, ; Robinson and Goodway, ; Robinson,and thus motor skills are not expected to strongly influence physical activity. In older children, perceived competence is more closely related to actual motor skills competence.
Older, low-skilled children are aware of their skills level and are more likely to perceive physical activity as difficult and challenging. Older children who are not equipped with the necessary skills to engage in physical activity that requires high levels of motor skills competence may not want to display their low competence publicly. As children transition into adolescence and early adulthood, the relationship between motor skills competence and physical activity may strengthen Stodden et al.
Investigators report moderate correlations between motor skills competence and physical activity in middle school—age children Reed et al. Okely and colleagues found that motor skills competence was significantly associated with participation in organized physical activity i. A strength of the model of Stodden and colleagues is the inclusion of factors related to psychosocial health and development that may influence the relationship between motor skills competence and physical activity, contributing to the development and maintenance of obesity.
Other studies have found that perceived competence plays a role in engagement in physical activity Ferrer-Caja and Weiss, ; Sollerhed et al. Motor skills competence is an important factor; however, it is only one of many factors that contribute to physical activity.
For instance, three studies have reported negative correlations between girls' motor competence and physical activity Reed et al. A possible explanation for these findings is that since girls tend to be less active than boys, it may be more difficult to detect differences in physical activity levels between high- and low-skilled girls.
It is also possible that out-of-school opportunities for physical activity are more likely to meet the interests of boys, which may at least partially explain sex differences in physical activity levels Le Masurier et al. Previous research suggests that in general boys are more motor competent than girls Graf et al.
One component of motor competence is the performance of gross motor skills, which are typically classified into object control and locomotor skills. Consistent evidence suggests that boys are more competent in object control skills, while girls are more competent in locomotor skills McKenzie et al. In light of these sex differences, it is important to examine the relationships of object control and locomotor skills with physical activity separately for boys and girls.
For boys, object control skills are more related to physical activity than are locomotor skills Hume et al. Three studies report a significant relationship between balance and physical activity for girls but not boys Reed et al. Cliff and colleagues suggest that object control and locomotor skills may be more related to boys' and girls' physical activity, respectively, because of the activity type in which each sex typically engages. The relationship between motor competence and physical activity clearly is complex.
It is quite likely that the relationship is dynamic and that motor competence increases the likelihood of participating in physical activity while at the same time engaging in physical activity provides opportunities to develop motor competence Stodden et al. Despite some uncertainty, the literature does reinforce the important role of physical education in providing developmentally appropriate movement opportunities in the school environment. These opportunities are the only means of engaging a large population of children and youth and providing them with the tools and opportunities that foster health, development, and future physical activity.
Stature Regular physical activity has no established effect on linear growth rate or ultimate height Malina, Although some studies suggest small differences, factors other than physical activity, especially maturity, often are not well controlled. It is important to note that regular physical activity does not have a negative effect on stature, as has sometimes been suggested.
Differences in height among children and adolescents participating in various sports are more likely due to the requirements of the sport, selection criteria, and interindividual variation in biological maturity than the effects of participation per se Malina et al.
Similarly, physique, as represented in somatotypes, does not appear to be significantly affected by physical activity during growth Malina et al. In contrast, components of weight can be influenced by regular physical activity, especially when the mode and intensity of the activity are tailored to the desired outcome.
Much of the available data in children and adolescents is based on BMI, a surrogate for composition, and indirect methods based on the two-compartment model of body composition in which body weight is divided into its fat-free and fat components Going et al. While studies generally support that physical activity is associated with greater fat-free mass and lower body fat, distinguishing the effects of physical activity on fat-free mass from expected changes associated with growth and maturation is difficult, especially during adolescence, when both sexes have significant growth in fat-free mass.
The application of methods based on the two-compartment model is fraught with errors, especially when the goal is to detect changes in fat-free mass, and no information is available from these methods regarding changes in the major tissue components of fat-free mass—muscle and skeletal tissue.
Muscle Skeletal muscle is the largest tissue mass in the body. It is the main energy-consuming tissue and provides the propulsive force for movement.
Postnatal muscle growth is explained largely by increases in cell size hypertrophy driving an increase in overall muscle mass. The increase in muscle mass with age is fairly linear from young childhood until puberty, with boys having a small but consistent advantage Malina, The sex difference becomes magnified during and after puberty, driven primarily by gender-related differences in sex steroids.
Muscle, as a percentage of body mass, increases from about 42 percent to 54 percent in boys between ages 5 and 11, whereas in girls it increases from about 40 percent to 45 percent between ages 5 and 13 and thereafter declines Malina et al. It should be noted that absolute mass does not decline; rather, the relative decline reflects the increase in the percentage of weight that is fat in girls.
At least part of the sex difference is due to differences in muscle development for different body regions Tanner et al. The growth rate of arm muscle tissue during adolescence in males is approximately twice that in females, whereas the sex difference in the growth of muscle tissue in the leg is much smaller. The sex difference that develops during puberty persists into adulthood and is more apparent for the musculature of the upper extremities.
Sex-related differences in muscular development contribute to differences in physical performance. Muscle strength develops in proportion to the cross-sectional area of muscle, and growth curves for strength are essentially the same as those for muscle Malina and Roche, Thus the sex difference in muscle strength is explained largely by differences in skeletal muscle mass rather than muscle quality or composition.
Aerobic endurance exercise has little effect on enhancing muscle mass but does result in significant improvement in oxygen extraction and aerobic metabolism Fournier et al. In contrast, numerous studies have shown that high-intensity resistance exercise induces muscle hypertrophy, with associated increases in muscle strength.
In children and adolescents, strength training can increase muscle strength, power, and endurance. Multiple types of resistance training modalities have proven effective and safe Bernhardt et al. These adaptations are due to muscle fiber hypertrophy and neural adaptations, with muscle hypertrophy playing a more important role in adolescents, especially in males. Prior to puberty, before the increase in anabolic sex steroid concentrations, neural adaptations explain much of the improvement in muscle function with exercise in both boys and girls.
Skeleton The skeleton is the permanent supportive framework of the body. It provides protection for vital organs and is the main mineral reservoir.
Bone tissue constitutes most of the skeleton, accounting for percent of body weight across the life span Trotter and Peterson, ; Trotter and Hixon, Skeletal strength, which dictates fracture risk, is determined by both the material and structural properties of bone, both of which are dependent on mineral accrual.
The relative mineral content of bone does not differ much among infants, children, adolescents, and adults, making up percent of the dry, fat-free weight of the skeleton Malina, As a fraction of weight, bone mineral the ash weight of bone represents about 2 percent of body weight in infants and about percent of body weight in adults Malina, Bone mineral content increases fairly linearly with age, with no sex difference during childhood.
Girls have, on average, a slightly greater bone mineral content than boys in early adolescence, reflecting their earlier adolescent growth spurt. The increase in total body bone mineral is explained by both increases in skeletal length and width and a small increase in bone mineral density Malina et al. Many studies have shown a positive effect of physical activity on intermediate markers of bone health, such as bone mineral content and density.
Active children and adolescents have greater bone mineral content and density than their less active peers, even after controlling for differences in height and muscle mass Wang et al. Exercise interventions support the findings from observational studies showing beneficial effects on bone mineral content and density in exercise participants versus controls Petit et al.
The relationship between greater bone mineral density and bone strength is unclear, as bone strength cannot be measured directly in humans. Thus, whether the effects of physical activity on bone mineral density translate into similar benefits for fracture risk is uncertain Karlsson, Animal studies have shown that loading causes small changes in bone mineral content and bone mineral density that result in large increases in bone strength, supporting the notion that physical activity probably affects the skeleton in a way that results in important gains in bone strength Umemura et al.
The relatively recent application of peripheral quantitative computed tomography for estimating bone strength in youth has also provided some results suggesting an increase in bone strength with greater than usual physical activity Sardinha et al.
The intensity of exercise appears to be a key determinant of the osteogenic response Turner and Robling, Bone tissue, like other tissues, accommodates to usual daily activities. Far fewer randomized controlled trials RCTs examining this relationship have been conducted in children than in adults, and there is little evidence on dose response to show how the type of exercise interacts with frequency, intensity, and duration.
Taken together, however, the available evidence supports beneficial effects of physical activity in promoting bone development Bailey et al.
Physical activity may reduce osteoporosis-related fracture risk by increasing bone mineral accrual during development; by enhancing bone strength; and by reducing the risk of falls by improving muscle strength, flexibility, coordination, and balance Bloomfield et al. Early puberty is a key developmental period. Approximately 26 percent of the mineral content in the adult skeleton is accrued during the 2 years around the time of peak height velocity Bailey et al.
This amount of mineral accrual represents approximately the same amount of bone mineral that most people will lose in their entire adult lives Arlot et al. The increase in mineral contributes to increased bone strength. Mineral is accrued on the periosteal surface of bone, such that the bone grows wider.
Increased bone width, independent of the increased mineral mass, also contributes to greater bone strength. Indeed, an increase of as little as 1 mm in the outer surface of bone increases strength substantially. Adding bone to the endosteal surface also increases strength Parfitt, ; Wang et al. Increases in testosterone may be a greater stimulus of periosteal expansion than estrogen since testosterone contributes to wider and stronger bones in males compared with females.
RCTs on this issue are few, although the available data are promising McKay et al. Thus, impact exercise begun in childhood may result in lasting structural changes that may contribute to increased bone strength and decreased fracture risk later in life Turner and Robling, ; Ferrari et al. Adipocytes are distributed throughout the body in various organs and tissues, although they are largely clustered anatomically in structures called fat depots, which include a large number of adipocytes held together by a scaffold-like structure of collagen and other structural molecules.
In the traditional view of the adipocyte, the cell provides a storage structure for fatty acids in the form of triacylglycerol molecules, with fatty acids being released when metabolic fuel is needed Arner and Eckel, The role of adipocytes in regulation of energy balance and in carbohydrate and lipid metabolism and the potential effects of physical activity on adipocyte function are of particular interest here, given growing concerns related to pediatric and adult obesity Ogden et al.
Adipocytes increase in size hypertrophy and number hyperplasia from birth through childhood and adolescence and into young adulthood to accommodate energy storage needs. In total the adipose organ contains about 0. There is wide interindividual variation, however, and the difficulty of investigating changes in the number and size of adipocytes is obvious given the invasiveness of the required biopsy procedures; understandably, then, data on these topics are scarce in children and adolescents.
Also, since only subcutaneous depots are accessible, results must be extrapolated from a few sites. Based on such information, the average size of adipocytes has been reported to increase two- to threefold in the first year of life, with little increase in nonobese boys and girls until puberty Malina et al. A small increase in average adipocyte size at puberty is more obvious in girls than in boys. There is considerable variation in size across various subcutaneous sites and between subcutaneous and internal depots.
The number of adipocytes is difficult to estimate. Available data suggest that the cellularity of adipose tissue does not increase significantly in early postnatal life Malina et al. Thus, gain in fat mass is the result of an increase in the size of existing adipocytes. From about years of age and continuing through early and middle childhood, the number of adipocytes increases gradually two- to threefold. With puberty the number practically doubles, followed by a plateau in late adolescence and early adulthood.
The number of adipocytes is similar in boys and girls until puberty, when girls experience a greater increase than boys. Their findings indicate that academic performance was unaffected by enrollment in physical education classes, which were found to average only 19 minutes of vigorous- or moderate-intensity physical activity. When time spent engaged in vigorous- or moderate-intensity physical activity outside of school was considered, however, a significant positive relation to academic performance emerged, with more time engaged in vigorous- or moderate-intensity physical activity being related to better grades but not test scores Coe et al.
Studies of participation in sports and academic achievement have found positive associations Mechanic and Hansell, ; Dexter, ; Crosnoe, ; Eitle and Eitle, ; Stephens and Schaben, ; Eitle, ; Miller et al.
Other studies, however, have found no association between participation in sports and academic performance Fisher et al. The findings of these studies need to be interpreted with caution as many of their designs failed to account for the level of participation by individuals in the sport e. Further, it is unclear whether policies required students to have higher GPAs to be eligible for participation. Offering sports opportunities is well justified regardless of the cognitive benefits, however, given that adolescents may be less likely to engage in risky behaviors when involved in sports or other extracurricular activities Page et al.
Although a consensus on the relationship of physical activity to academic achievement has not been reached, the vast majority of available evidence suggests the relationship is either positive or neutral.
The meta-analytic review by Fedewa and Ahn suggests that interventions entailing aerobic physical activity have the greatest impact on academic performance; however, all types of physical activity, except those involving flexibility alone, contribute to enhanced academic performance, as do interventions that use small groups about 10 students rather than individuals or large groups.
Regardless of the strength of the findings, the literature indicates that time spent engaged in physical activity is beneficial to children because it has not been found to detract from academic performance, and in fact can improve overall health and function Sallis et al.
Single Bouts of Physical Activity Beyond formal physical education, evidence suggests that multi-component approaches are a viable means of providing physical activity opportunities for children across the school curriculum see also Chapter 6.
Although health-related fitness lessons taught by certified physical education teachers result in greater student fitness gains relative to such lessons taught by other teachers Sallis et al. Single sessions or bouts of physical activity have independent merit, offering immediate benefits that can enhance the learning experience.
Studies have found that single bouts of physical activity result in improved attention Hillman et al. Yet single bouts of physical activity have differential effects, as very vigorous exercise has been associated with cognitive fatigue and even cognitive decline in adults Tomporowski, As seen in Figurehigh levels of effort, arousal, or activation can influence perception, decision making, response preparation, and actual response.
For discussion of the underlying constructs and differential effects of single bouts of physical activity on cognitive performance, see Tomporowski Diagram of a simplified version of Sanders's cognitive-energetic model of human information processing adapted from Jones and Hardy, For children, classrooms are busy places where they must distinguish relevant information from distractions that emerge from many different sources occurring simultaneously.
A student must listen to the teacher, adhere to classroom procedures, focus on a specific task, hold and retain information, and make connections between novel information and previous experiences. Hillman and colleagues demonstrated that a single bout of moderate-intensity walking 60 percent of maximum heart rate resulted in significant improvements in performance on a task requiring attentional inhibition e. These findings were accompanied by changes in neuroelectric measures underlying the allocation of attention see Figure and significant improvements on the reading subtest of the Wide Range Achievement Test.
No such effects were observed following a similar duration of quiet rest. These findings were later replicated and extended to demonstrate benefits for both mathematics and reading performance in healthy children and those diagnosed with attention deficit hyperactivity disorder Pontifex et al.
Further replications of these findings demonstrated that a single bout of moderate-intensity exercise using a treadmill improved performance on a task of attention and inhibition, but similar benefits were not derived from moderate-intensity exercise that involved exergaming O'Leary et al. It was also found that such benefits were derived following cessation of, but not during, the bout of exercise Drollette et al. The applications of such empirical findings within the school setting remain unclear.
A randomized controlled trial entitled Physical Activity Across the Curriculum PAAC used cluster randomization among 24 schools to examine the effects of physically active classroom lessons on BMI and academic achievement Donnelly et al. The academically oriented physical activities were intended to be of vigorous or moderate intensity 3—6 metabolic equivalents [METs] and to last approximately 10 minutes and were specifically designed to supplement content in mathematics, language arts, geography, history, spelling, science, and health.
The study followed boys and girls for 3 years as they rose from 2nd or 3rd to 4th or 5th grades. Changes in academic achievement, fitness, and blood screening were considered secondary outcomes. During a 3-year period, students who engaged in physically active lessons, on average, improved their academic achievement by 6 percent, while the control groups exhibited a 1 percent decrease. FIGURE Change in academic scores from baseline after physically active classroom lessons in elementary schools in northeast Kansas — It is important to note that cognitive tasks completed before, during, and after physical activity show varying effects, but the effects were always positive compared with sedentary behavior.
In a study carried out by Drollette and colleagues36 preadolescent children completed two cognitive tasks—a flanker task to assess attention and inhibition and a spatial nback task to assess working memory—before, during, and after seated rest and treadmill walking conditions. The children sat or walked on different days for an average of 19 minutes. The results suggest that the physical activity enhanced cognitive performance for the attention task but not for the task requiring working memory.
Accordingly, although more research is needed, the authors suggest that the acute effects of exercise may be selective to certain cognitive processes i. Indeed, data collected using a task-switching paradigm i. Thus, findings to date indicate a robust relationship of acute exercise to transient improvements in attention but appear inconsistent for other aspects of cognition.
Academic Learning Time and On- and Off-Task Behaviors Excessive time on task, inattention to task, off-task behavior, and delinquency are important considerations in the learning environment given the importance of academic learning time to academic performance. These behaviors are observable and of concern to teachers as they detract from the learning environment.
Systematic observation by trained observers may yield important insight regarding the effects of short physical activity breaks on these behaviors. Indeed, systematic observations of student behavior have been used as an alternative means of measuring academic performance Mahar et al.
After the development of classroom-based physical activities, called Energizers, teachers were trained in how to implement such activities in their lessons at least twice per week Mahar et al. Measurements of baseline physical activity and on-task behaviors were collected in two 3rd-grade and two 4th-grade classes, using pedometers and direct observation.
The intervention included students, while served as controls by not engaging in the activities. A subgroup of 62 3rd and 4th graders was observed for on-task behavior in the classroom following the physical activity. Children who participated in Energizers took more steps during the school day than those who did not; they also increased their on-task behaviors by more than 20 percent over baseline measures.
A systematic review of a similar in-class, academically oriented, physical activity plan—Take 10! The findings suggest that children who experienced Take 10! Further, children in the Take 10! Some have expressed concern that introducing physical activity into the classroom setting may be distracting to students.
Yet in one study it was sedentary students who demonstrated a decrease in time on task, while active students returned to the same level of on-task behavior after an active learning task Grieco et al.
Among the 97 3rd-grade students in this study, a small but nonsignificant increase in on-task behaviors was seen immediately following these active lessons. Additionally, these improvements were not mediated by BMI. In sum, although presently understudied, physically active lessons may increase time on task and attention to task in the classroom setting.
Given the complexity of the typical classroom, the strategy of including content-specific lessons that incorporate physical activity may be justified.
Recess It is recommended that every child have 20 minutes of recess each day and that this time be outdoors whenever possible, in a safe activity NASPE, Consistent engagement in recess can help students refine social skills, learn social mediation skills surrounding fair play, obtain additional minutes of vigorous- or moderate-intensity physical activity that contribute toward the recommend 60 minutes or more per day, and have an opportunity to express their imagination through free play Pellegrini and Bohn, ; see also Chapter 6.
When children participate in recess before lunch, additional benefits accrue, such as less food waste, increased incidence of appropriate behavior in the cafeteria during lunch, and greater student readiness to learn upon returning to the classroom after lunch Getlinger et al. To examine the effects of engagement in physical activity during recess on classroom behavior, Barros and colleagues examined data from the Early Childhood Longitudinal Study on 10, 8- to 9-year-old children.
Results indicate that children who had at least 15 minutes of recess were more likely to exhibit appropriate behavior in the classroom Barros et al. In another study, 43 4th-grade students were randomly assigned to 1 or no days of recess to examine the effects on classroom behavior Jarrett et al.
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The researchers concluded that on-task behavior was better among the children who had recess. In a series of studies examining kindergartners' attention to task following a minute recess, increased time on task was observed during learning centers and story reading Pellegrini et al. Despite these positive findings centered on improved attention, it is important to note that few of these studies actually measured the intensity of the physical activity during recess.
From a slightly different perspective, survey data from Virginia elementary school principals suggest that time dedicated to student participation in physical education, art, and music did not negatively influence academic performance Wilkins et al. Thus, the strategy of reducing time spent in physical education to increase academic performance may not have the desired effect. The evidence on in-school physical activity supports the provision of physical activity breaks during the school day as a way to increase fluid intelligence, time on task, and attention.
New technology has emerged that has allowed scientists to understand the impact of lifestyle factors on the brain from the body systems level down to the molecular level. A greater understanding of the cognitive components that subserve academic performance and may be amenable to intervention has thereby been gained. Research conducted in both laboratory and field settings has helped define this line of inquiry and identify some preliminary underlying mechanisms.
The Evidence Base on the Relationship of Physical Activity to Brain Health and Cognition in Older Adults Despite the current focus on the relationship of physical activity to cognitive development, the evidence base is larger on the association of physical activity with brain health and cognition during aging.
Much can be learned about how physical activity affects childhood cognition and scholastic achievement through this work. Despite earlier investigations into the relationship of physical activity to cognitive aging see Etnier et al. Specifically, older adults aged 60 and 75 were randomly assigned to a 6-month intervention of either walking i.
The walking group but not the flexibility group showed improved cognitive performance, measured as a shorter response time to the presented stimulus. Results from a series of tasks that tapped different aspects of cognitive control indicated that engagement in physical activity is a beneficial means of combating cognitive aging Kramer et al.
Cognitive control, or executive control, is involved in the selection, scheduling, and coordination of computational processes underlying perception, memory, and goal-directed action.
These processes allow for the optimization of behavioral interactions within the environment through flexible modulation of the ability to control attention MacDonald et al. Core cognitive processes that make up cognitive control or executive control include inhibition, working memory, and cognitive flexibility Diamond,processes mediated by networks that involve the prefrontal cortex.
Inhibition or inhibitory control refers to the ability to override a strong internal or external pull so as to act appropriately within the demands imposed by the environment Davidson et al. For example, one exerts inhibitory control when one stops speaking when the teacher begins lecturing.
Working memory refers to the ability to represent information mentally, manipulate stored information, and act on the information Davidson et al. In solving a difficult mathematical problem, for example, one must often remember the remainder. Finally, cognitive flexibility refers to the ability to switch perspectives, focus attention, and adapt behavior quickly and flexibly for the purposes of goal-directed action Blair et al. For example, one must shift attention from the teacher who is teaching a lesson to one's notes to write down information for later study.
Based on their earlier findings on changes in cognitive control induced by aerobic training, Colcombe and Kramer conducted a meta-analysis to examine the relationship between aerobic training and cognition in older adults aged using data from 18 randomized controlled exercise interventions. Their findings suggest that aerobic training is associated with general cognitive benefits that are selectively and disproportionately greater for tasks or task components requiring greater amounts of cognitive control.
A second and more recent meta-analysis Smith et al. In older adults, then, aerobic training selectively improves cognition. Hillman and colleagues examined the relationship between physical activity and inhibition one aspect of cognitive control using a computer-based stimulus-response protocol in individuals aged Their results indicate that greater amounts of physical activity are related to decreased response speed across task conditions requiring variable amounts of inhibition, suggesting a generalized relationship between physical activity and response speed.
In addition, the authors found physical activity to be related to better accuracy across conditions in older adults, while no such relationship was observed for younger adults.
Of interest, this relationship was disproportionately larger for the condition requiring greater amounts of inhibition in the older adults, suggesting that physical activity has both a general and selective association with task performance Hillman et al.
With advances in neuroimaging techniques, understanding of the effects of physical activity and aerobic fitness on brain structure and function has advanced rapidly over the past decade.
In particular, a series of studies Colcombe et al. Normal aging results in the loss of brain tissue Colcombe et al.
Thus cognitive functions subserved by these brain regions such as those involved in cognitive control and aspects of memory are expected to decay more dramatically than other aspects of cognition.
Colcombe and colleagues investigated the relationship of aerobic fitness to gray and white matter tissue loss using magnetic resonance imaging MRI in 55 healthy older adults aged They observed robust age-related decreases in tissue density in the frontal, temporal, and parietal regions using voxel-based morphometry, a technique used to assess brain volume. Reductions in the amount of tissue loss in these regions were observed as a function of fitness.
Given that the brain structures most affected by aging also demonstrated the greatest fitness-related sparing, these initial findings provide a biological basis for fitness-related benefits to brain health during aging.
In a second study, Colcombe and colleagues examined the effects of aerobic fitness training on brain structure using a randomized controlled design with 59 sedentary healthy adults aged The treatment group received a 6-month aerobic exercise i. Results indicated that gray and white matter brain volume increased for those who received the aerobic fitness training intervention. No such results were observed for those assigned to the stretching and toning group. Specifically, those assigned to the aerobic training intervention demonstrated increased gray matter in the frontal lobes, including the dorsal anterior cingulate cortex, the supplementary motor area, the middle frontal gyrus, the dorsolateral region of the right inferior frontal gyrus, and the left superior temporal lobe.
White matter volume changes also were evidenced following the aerobic fitness intervention, with increases in white matter tracts being observed within the anterior third of the corpus callosum. These brain regions are important for cognition, as they have been implicated in the cognitive control of attention and memory processes.
These findings suggest that aerobic training not only spares age-related loss of brain structures but also may in fact enhance the structural health of specific brain regions. In addition to the structural changes noted above, research has investigated the relationship between aerobic fitness and changes in brain function. That is, aerobic fitness training has also been observed to induce changes in patterns of functional activation.
Functional MRI fMRI measures, which make it possible to image activity in the brain while an individual is performing a cognitive task, have revealed that aerobic training induces changes in patterns of functional activation.
This approach involves inferring changes in neuronal activity from alteration in blood flow or metabolic activity in the brain. In a seminal paper, Colcombe and colleagues examined the relationship of aerobic fitness to brain function and cognition across two studies with older adults.
In the second study, 29 participants aged were recruited and randomly assigned to either a fitness training i. In both studies, participants were given a task requiring variable amounts of attention and inhibition.
Results indicated that fitness study 1 and fitness training study 2 were related to greater activation in the middle frontal gyrus and superior parietal cortex; these regions of the brain are involved in attentional control and inhibitory functioning, processes entailed in the regulation of attention and action.
These changes in neural activation were related to significant improvements in performance on the cognitive control task of attention and inhibition. Taken together, the findings across studies suggest that an increase in aerobic fitness, derived from physical activity, is related to improvements in the integrity of brain structure and function and may underlie improvements in cognition across tasks requiring cognitive control.
Although developmental differences exist, the general paradigm of this research can be applied to early stages of the life span, and some early attempts to do so have been made, as described below.
Given the focus of this chapter on childhood cognition, it should be noted that this section has provided only a brief and arguably narrow look at the research on physical activity and cognitive aging. Considerable work has detailed the relationship of physical activity to other aspects of adult cognition using behavioral and neuroimaging tools e. The interested reader is referred to a number of review papers and meta-analyses describing the relationship of physical activity to various aspects of cognitive and brain health Etnier et al.
Child Development, Brain Structure, and Function Certain aspects of development have been linked with experience, indicating an intricate interplay between genetic programming and environmental influences. During typical development, experience shapes the pruning process through the strengthening of neural networks that support relevant thoughts and actions and the elimination of unnecessary or redundant connections.
Examples of neural plasticity in response to unique environmental interaction have been demonstrated in human neuroimaging studies of participation in music Elbert et al. Effects of Regular Engagement in Physical Activity and Physical Fitness on Brain Structure Recent advances in neuroimaging techniques have rapidly advanced understanding of the role physical activity and aerobic fitness may have in brain structure. In children a growing body of correlational research suggests differential brain structure related to aerobic fitness.
Chaddock and colleagues ab showed a relationship among aerobic fitness, brain volume, and aspects of cognition and memory. Specifically, Chaddock and colleagues a assigned 9- to year-old preadolescent children to lower- and higher-fitness groups as a function of their scores on a maximal oxygen uptake VO2max test, which is considered the gold-standard measure of aerobic fitness.
They observed larger bilateral hippocampal volume in higher-fit children using MRI, as well as better performance on a task of relational memory. It is important to note that relational memory has been shown to be mediated by the hippocampus Cohen and Eichenbaum, ; Cohen et al. Further, no differences emerged for a task condition requiring item memory, which is supported by structures outside the hippocampus, suggesting selectivity among the aspects of memory that benefit from higher amounts of fitness.
Lastly, hippocampal volume was positively related to performance on the relational memory task but not the item memory task, and bilateral hippocampal volume was observed to mediate the relationship between fitness and relational memory Chaddock et al. Such findings are consistent with behavioral measures of relational memory in children Chaddock et al.
In a second investigation Chaddock et al. The authors observed differential findings in the basal ganglia, a subcortical structure involved in the interplay of cognition and willed action. Specifically, higher-fit children exhibited greater volume in the dorsal striatum i. Such findings are not surprising given the role of the dorsal striatum in cognitive control and response resolution Casey et al.
Chaddock and colleagues b further observed that higher-fit children exhibited increased inhibitory control and response resolution and that higher basal ganglia volume was related to better task performance. These findings indicate that the dorsal striatum is involved in these aspects of higher-order cognition and that fitness may influence cognitive control during preadolescent development.
Effects of Regular Engagement in Physical Activity and Physical Fitness on Brain Function Other research has attempted to characterize fitness-related differences in brain function using fMRI and event-related brain potentials ERPswhich are neuroelectric indices of functional brain activation in the electro-encephalographic time series.
To date, few randomized controlled interventions have been conducted. Notably, Davis and colleagues conducted one such intervention lasting approximately 14 weeks that randomized 20 sedentary overweight preadolescent children into an after-school physical activity intervention or a nonactivity control group.
The fMRI data collected during an antisaccade task, which requires inhibitory control, indicated increased bilateral activation of the prefrontal cortex and decreased bilateral activation of the posterior parietal cortex following the physical activity intervention relative to the control group. Such findings illustrate some of the neural substrates influenced by participation in physical activity.
Two additional correlational studies Voss et al. That is, Chaddock and colleagues observed increased activation in prefrontal and parietal brain regions during early task blocks and decreased activation during later task blocks in higher-fit relative to lower-fit children.
Given that higher-fit children outperformed lower-fit children on the aspects of the task requiring the greatest amount of cognitive control, the authors reason that the higher-fit children were more capable of adapting neural activity to meet the demands imposed by tasks that tapped higher-order cognitive processes such as inhibition and goal maintenance. Voss and colleagues used a similar task to vary cognitive control requirements and found that higher-fit children outperformed their lower-fit counterparts and that such differences became more pronounced during task conditions requiring the upregulation of control.
Further, several differences emerged across various brain regions that together make up the network associated with cognitive control. Collectively, these differences suggest that higher-fit children are more efficient in the allocation of resources in support of cognitive control operations. Other imaging research has examined the neuroelectric system i.
Several studies Hillman et al. Classical theory suggests that P3 relates to neuronal activity associated with revision of the mental representation of the previous event within the stimulus environment Donchin, P3 amplitude reflects the allocation of attentional resources when working memory is updated Donchin and Coles, such that P3 is sensitive to the amount of attentional resources allocated to a stimulus Polich, ; Polich and Heine, P3 latency generally is considered to represent stimulus evaluation and classification speed Kutas et al.
Therefore the above findings suggest that higher-fit children allocate greater attentional resources and have faster cognitive processing speed relative to lower-fit children Hillman et al. Given that higher-fit children also demonstrate better performance on cognitive control tasks, the P3 component appears to reflect the effectiveness of a subset of cognitive systems that support willed action Hillman et al.