Children and Adolescents in Exercise

Growth, Development, and Maturation in Children and Adolescents:

Throughout this chapter, we explore the physiological responses and adaptations to exercise in children and adolescents, focusing on the differences and similarities between this age group and adults. Pediatric exercise physiologists have made significant contributions to our understanding of how children and adolescents respond to physical activity, which is particularly important given the role of exercise in combatting childhood obesity and promoting lifelong healthy habits.

Growth, Development, and Maturation:

  • Growth: Refers to the increase in the size of the body or its parts. It involves physical growth in terms of height, weight, and body proportions.
  • Development: Involves the differentiation of cells along specialized lines of function, which reflects functional changes occurring with growth. It includes the development of organ systems and physiological functions.
  • Maturation: This process involves taking on adult form and becoming fully functional, specific to the system or function being considered. Skeletal maturity, for instance, means having a fully developed skeletal system, while sexual maturity refers to a fully functional reproductive system.

Phases of Life:

  • Infancy: The first year of life.
  • Childhood: The period between the end of infancy (around the first birthday) and the onset of adolescence. Childhood is often divided into early childhood (preschool) and middle childhood (elementary school).
  • Adolescence: A period that varies in onset and termination but is generally defined by the onset of puberty (development of secondary sex characteristics) and ends with the completion of growth and development processes, such as attaining adult height. Adolescence typically spans from 8 to 19 years for girls and from 10 to 22 years for boys.

Understanding the physiological aspects of growth and development is crucial, especially in the context of youth sports and efforts to combat childhood obesity. Children and adolescents are not merely miniature versions of adults; their growth and development profoundly affect their physiological and performance capacities. As they grow in size, most of their functional capacities, including motor abilities, strength, cardiovascular and respiratory functions, and aerobic and anaerobic capacities, increase as well.

In the subsequent sections, we delve into age-related changes in various physical abilities in children, considering their physical state and growth and development of selected body tissues.

Growth, Height, and Weight:

Specialists in growth and development have extensively studied the changes in height and weight throughout childhood and adolescence, focusing on the rates of change in these two variables. Changes in height are measured in centimeters per year, while changes in weight are measured in kilograms per year.

  • Height Change: Height increases rapidly during the first two years of life, with a child reaching approximately 50% of adult height by age 2. Afterward, the rate of height increase progressively slows throughout childhood, resulting in a decline in the rate of change. Just before puberty, there is a marked increase in the rate of height change, followed by an exponential decrease in rate until full adult height is achieved, typically around age 16 for girls and 18 for boys, though some boys may continue growing into their early 20s. The peak rate of height growth occurs at around 12 years for girls and 14 years for boys.
  • Weight Change: The peak rate of weight growth occurs slightly later than that of height, at around 12.5 years for girls and 14.5 years for boys. This delayed peak in weight growth compared to height reflects the intricate changes that occur during adolescence.

Bone Development:

  • Bones and Ossification: Bones, joints, cartilage, and ligaments form the structural support of the body. Bones serve various functions, including muscle attachment points, protection of delicate tissues, calcium and phosphorus storage, and involvement in blood cell formation. Bone development begins in fetal development and continues through the initial 14 to 22 years of life through ossification, where membranes and cartilage transform into bone. The growth plate in bones plays a crucial role in this process.
  • Closing of Growth Plates: The average age at which growth plates close and ossification completes varies widely, but bones typically begin fusing in the preteen years and are fully fused by the early 20s. Girls tend to achieve full bone maturity several years earlier than boys due to hormonal differences, particularly estrogen’s role in signaling the growth plates to close.
  • Bone Structure: Mature long bones have a complex structure and are living tissues requiring essential nutrients and a rich blood supply. Bone consists of cells distributed within a lattice-like arrangement, and it is dense and hard due to deposits of calcium salts, primarily calcium phosphate and calcium carbonate. Adequate calcium intake is vital for bone health, especially during periods of growth and aging when bone mineral content can decrease, leading to increased fragility.
  • Bone Health: Bone health is evaluated through measures such as bone mineral density (BMD) and blood markers of bone formation and resorption. BMD significantly increases during childhood and adolescence, generally peaking in the second decade and declining later in life. Adolescence is a critical period for increasing BMD through proper nutrition and weight-bearing exercises, as illustrated in the potential long-term benefits of high-impact exercises such as box jumping during prepubescent years.

Understanding the changes in height, weight, and bone development in children and adolescents is essential for assessing their growth, physical development, and potential long-term health outcomes.

Muscle Growth and Development:

  • Birth to Adolescence: Muscle mass steadily increases from birth through adolescence, alongside overall body weight. In males, skeletal muscle mass increases from approximately 25% of total body weight at birth to about 40-45% or more in young men aged 20-30 years. The most significant muscle development occurs during puberty when testosterone production undergoes a sudden, nearly tenfold increase. In contrast, girls do not experience such rapid muscle growth during puberty, but their muscle mass continues to increase, albeit at a slower rate than boys, reaching about 30-35% of their total body weight as young adults. These gender differences are largely attributed to hormonal variations during puberty.
  • Muscle Growth Mechanisms: Increases in muscle mass primarily result from hypertrophy, which involves an increase in the size of existing muscle fibers, with limited or no hyperplasia (an increase in the number of muscle fibers). Hypertrophy occurs due to an increase in myofilaments and myofibrils within the muscle fibers. As young bones elongate, muscle length increases through the addition of sarcomeres at the muscle-tendon junction and the lengthening of existing sarcomeres. Muscle mass typically peaks in females between ages 16 to 20 and in males between ages 18 to 25, unless it is further increased through factors like exercise and diet.

Fat Accumulation:

  • Fat Development: The formation of fat cells and the deposition of fat in these cells begin during fetal development and continue throughout life. Each fat cell can increase in size at any age. The amount of fat accumulated in the body is influenced by diet, exercise habits, and heredity.
  • Fat Distribution with Growth and Aging: At birth, approximately 10-12% of total body weight consists of fat. By the time of physical maturity, fat content increases to approximately 15% of total body weight in males and approximately 25% in females. This gender difference in fat accumulation, similar to muscle growth, is primarily attributed to hormonal variations. During puberty, girls experience increased estrogen levels and tissue exposure, which promote the deposition of body fat.
  • Changes in Body Fat Percentage: It is important to note that both fat mass and fat-free mass increase during this period, meaning that an increase in absolute fat does not necessarily equate to an increase in relative fat.

Understanding the patterns of muscle growth and fat accumulation during childhood and adolescence is essential for assessing physical development, hormonal influences, and the potential impact of factors like exercise and diet on body composition.

Nervous System Development:

  • Balance, Agility, and Coordination: As children grow, they undergo improvements in balance, agility, and coordination as a result of the ongoing development of their nervous systems. These enhancements are essential for performing skilled and precise movements.
  • Role of Myelination: Myelination, the process of forming a protective sheath around nerve fibers, is crucial for efficient nerve signal transmission. It must be completed for fast reactions and the execution of skilled movements because the conduction of nerve impulses along fibers is significantly slower in the absence or incomplete myelination. Myelination of nerve fibers, including those in the cerebral cortex, occurs most rapidly during childhood but continues beyond puberty.
  • Impact on Skill Development: While practicing an activity or skill can lead to performance improvements to some extent, the full development of these activities or skills depends on the full maturation and myelination of the nervous system. This maturation is necessary for achieving a high level of proficiency in various motor skills.
  • Strength Development: The development of strength in children is also likely influenced by the process of myelination. Efficient neural communication, facilitated by myelination, is essential for the recruitment and activation of muscle fibers during strength-related activities.

Understanding the role of myelination and the maturation of the nervous system is essential for comprehending the progression of motor skills, balance, agility, coordination, and strength in children as they grow and develop.

Strength Development in Children and Adolescents:

  • Improvement with Age: Strength development in children and adolescents is closely linked to the increase in muscle mass as they grow. As they age, their muscle strength generally improves.
  • Puberty-Related Strength Increase: During puberty, both boys and girls experience marked increases in strength. In pubescent males, these increases are particularly significant due to the development of increased muscle mass.
  • Role of Hormones: Hormonal changes during puberty, such as increased testosterone production in males, contribute to the substantial strength gains observed in pubescent individuals.
  • Neural Maturity: The extent of muscle development and performance capacity also depends on the relative maturation of the nervous system. The neural control of muscle function is limited before sexual maturity, primarily because myelination of many motor nerves is incomplete.
  • Sex Differences: Longitudinal data on strength development are more readily available for boys than for girls. Cross-sectional data suggest that girls experience a more gradual and linear increase in absolute strength and do not exhibit significant changes in strength relative to body weight after puberty.

Understanding the patterns of strength development in children and adolescents is essential for designing age-appropriate training programs and recognizing the influence of factors like hormones and neural maturity on strength gains during growth and development.

Cardiovascular and Respiratory Function in Children and Adolescents:

Cardiovascular function goes through significant changes as children grow and age, particularly in terms of aerobic power. These changes impact their ability to perform both submaximal and maximal exercise.

Rest and Submaximal Exercise:

  • Blood Pressure: Blood pressure levels at rest and during submaximal exercise are lower in children compared to adults. However, these levels progressively increase to reach adult values during the late teenage years. The relationship between blood pressure and body size is direct, meaning that larger individuals tend to have higher blood pressure levels. Therefore, children’s lower blood pressure values can be partially attributed to their smaller size.
  • Blood Flow: During exercise, blood flow to active muscles in children can be more substantial relative to muscle volume compared to adults. This phenomenon arises because children have less peripheral resistance. As a result, for a given submaximal workload, children experience lower blood pressure, and their muscles are relatively overperfused with blood.
  • Cardiac Output: Cardiac output, which is the product of heart rate and stroke volume (the volume of blood pumped per heartbeat), is influenced by the child’s heart size and total blood volume. In children, both heart size and blood volume are smaller, leading to lower stroke volumes at rest and during exercise compared to adults.
  • Heart Rate Response: To compensate for the lower stroke volume and maintain adequate cardiac output, children exhibit a higher heart rate response to a given rate of submaximal work, such as during cycling on an ergometer. This higher heart rate response is observed when the absolute oxygen requirement matches that of an adult. As children grow and their heart size and blood volume increase along with their body size, stroke volume also increases, resulting in a decreased heart rate response.
  • Cardiac Output in Children: Despite the higher submaximal heart rate, children’s cardiac output remains somewhat lower than that of adults when performing the same absolute rate of work or oxygen consumption. To ensure sufficient oxygen uptake during submaximal exercise, children rely on an increased arterial-mixed venous oxygen difference (a-v¯O2 difference). This difference indicates that a larger percentage of the cardiac output is directed to the active muscles, compensating for the lower stroke volume.

Understanding these cardiovascular and respiratory differences in children and adolescents compared to adults is crucial for designing appropriate exercise programs and assessing their physiological responses during various levels of physical activity.

Maximal Exercise in Children and Adolescents:

During maximal exercise, children and adolescents exhibit distinct characteristics compared to adults. These differences are essential to consider when evaluating their exercise performance and physiological responses.

  • Maximum Heart Rate (HRmax): Children have a higher maximum heart rate (HRmax) than adults. It’s not uncommon for children under the age of 10 to have HRmax values exceeding 210 beats per minute. In contrast, the average 20-year-old adult typically has an HRmax of around 195 beats per minute. As children age, their HRmax decreases linearly. Cross-sectional studies suggest a decline of slightly less than 1 beat per minute per year in adults aged 25-30 and older. However, longitudinal studies propose a slower decrease of 0.5 beats per minute per year. This decline in HRmax over one’s life is due to a reduced sensitivity of cardiac beta-adrenergic receptors.
  • Maximal Stroke Volume Limitation: During maximal exercise, children’s smaller hearts and blood volumes limit the maximal stroke volume they can achieve. Despite their high HRmax, it cannot fully compensate for this limitation, resulting in children having a lower maximal cardiac output compared to adults. This limitation becomes more evident at high absolute workloads, such as pedaling at 100 watts on a cycle ergometer or aiming for the same absolute oxygen consumption (VO2) as adults. The child’s capacity for oxygen delivery is thus less than that of an adult, impacting their performance at such workloads.
  • Relative Workloads: In contrast, at high relative workloads where the child is primarily responsible for moving their body mass (e.g., running on a treadmill at the same speed with no grade), the limitation posed by the lower maximal cardiac output is not as significant. For instance, in running, a 25 kg (55 lb) child requires considerably less oxygen than a 90 kg (198 lb) adult man, proportional to their body size. However, when scaling for body size, the rate of oxygen consumption is approximately the same for both.

Understanding these differences in maximal exercise responses between children, adolescents, and adults is crucial for designing age-appropriate exercise programs and interpreting physiological responses during various levels of physical exertion in the younger population.

Lung Function in Children and Adolescents:

Lung function undergoes significant changes as children grow and develop. These changes are important to consider when assessing respiratory performance and capacity in the younger population.

  • Lung Volumes: All lung volumes increase as a child grows, reaching their peak values when growth is complete. The various lung volumes, such as tidal volume, inspiratory reserve volume, and expiratory reserve volume, all follow this pattern of growth. These changes in lung volumes are matched by corresponding changes in the highest ventilation that can be achieved during exhaustive exercise. This maximum ventilation, known as maximal expiratory ventilation (V . Emax) or maximal minute ventilation, increases with age until physical maturity and then starts to decrease with advancing age. For instance, at around 4-6 years of age, boys typically have an average V . Emax of about 40 liters per minute (L/min). However, at full maturity, this value increases substantially to a range of 110 to 140 L/min. Girls also exhibit a similar pattern of change, but their absolute values post-puberty tend to be lower due to their smaller body size. These alterations in lung volumes and V . Emax are closely related to the growth of the pulmonary system.
  • Growth and Lung Size: The growth of the pulmonary system in children parallels their overall growth patterns. As children grow and develop, their body size increases, leading to an increase in lung size and function. This growth is a natural part of the maturation process.

Understanding these changes in lung function is crucial for assessing respiratory health and capacity in children and adolescents. It helps healthcare professionals and educators tailor interventions and exercise programs to accommodate the specific needs of this population at different stages of development.

Metabolic Function and Aerobic Capacity in Children and Adolescents:

Metabolic function and substrate utilization, both at rest and during exercise, undergo changes as children and adolescents grow and develop. These changes are closely related to the alterations seen in muscle mass, strength, and cardiorespiratory function.

  • Aerobic Capacity (VO2max): Aerobic capacity, often measured as VO2max, represents the maximum amount of oxygen that an individual can utilize during intense exercise. With growth and development, cardiovascular and respiratory adaptations occur to accommodate the increased oxygen demands of exercising muscles. These changes suggest that aerobic capacity should increase as well.
  • Peak VO2max: Early studies, such as one conducted by Robinson in 1938, observed that V . O2max peaks between the ages of 17 and 21 in boys and then decreases linearly with age. Subsequent research confirmed these findings. In girls and women, a similar trend is observed, with a decline in aerobic capacity starting at a younger age, generally around 12 to 15.
  • Relative VO2max: Expressing VO2max relative to body weight (ml · kg–1 · min–1) provides a different perspective. For boys, little change in relative VO2max occurs from age 6 to young adulthood. In girls, there is minimal change from age 6 to 13, but after age 13, a gradual decrease is observed. These changes in relative VO2max may reflect sex differences in increasing body mass and changing body composition.
  • Limitations of Body Weight Normalization: There are concerns about the validity of using body weight to scale VO2max for differences in size during periods of growth and development. Arguments against this practice include the fact that VO2max values expressed relative to body weight may remain stable or decline with age, despite improvements in endurance performance. Additionally, the relationship between VO2max, body dimensions, and physiological functions during growth is complex, and body weight may not be the most appropriate way to account for differences in body size in children and adolescents.

Understanding the nuances of how metabolic function and aerobic capacity change during growth and development is crucial for assessing the fitness and health of children and adolescents. It helps professionals appropriately tailor exercise programs and interventions to accommodate the unique needs of this population at different stages of their physical development.

Running Economy in Children and Adolescents:

Running economy is a critical factor in a child’s or adolescent’s performance in activities like distance running. It refers to the efficiency of their energy utilization while running at a fixed speed. Understanding how growth-related changes in aerobic capacity impact a child’s running economy is essential for assessing their athletic performance.

  • Aerobic Capacity and Endurance Performance: In activities that require a fixed rate of work, such as cycling on an ergometer, a child’s lower VO2max (aerobic capacity) can limit their endurance performance. This is because VO2max determines the maximum amount of oxygen that can be supplied to the working muscles. A lower VO2max means that oxygen delivery to muscles is limited, impacting performance.
  • Running vs. Cycling: However, for activities like distance running where body weight is the primary resistance to movement, children may not necessarily be at a disadvantage due to their lower VO2max values. This is because when VO2max is expressed relative to body weight (ml · kg–1 · min–1), children’s values are often already at or near adult levels. In this context, their aerobic capacity per unit of body weight is comparable to that of adults.
  • Running Economy Improvement: Children can still maintain a competitive running pace compared to adults due to differences in running economy. Running economy refers to how efficiently a person utilizes energy while running at a specific speed. Several factors contribute to this improvement:
    • Growth-Related Changes: As children grow, their legs lengthen, their muscles become stronger, and their running skills improve. These growth-related changes contribute to improved running economy.
    • Stride Frequency: One of the most crucial factors in improving running economy as children grow is increased stride frequency. Children and adolescents naturally increase their stride frequency as they develop, which enhances their running efficiency.
  • Considerations About Scaling: It’s worth noting that scaling oxygen consumption to body weight during growth and development may not be the most appropriate approach. The relationship between aerobic capacity, body dimensions, and physiological functions during growth is complex. Therefore, using body weight as the sole factor to account for differences in body size in children and adolescents may not accurately reflect their athletic performance.

While children may have a lower absolute aerobic capacity compared to adults, their running economy can improve significantly as they grow and develop. Factors like increased stride frequency and improved running skills play a crucial role in allowing children and adolescents to maintain competitive running paces, even without a proportional increase in VO2max.

Anaerobic Capacity in Children and Adolescents:

Anaerobic capacity refers to the ability to perform short, high-intensity activities that rely primarily on non-oxygen-dependent energy pathways. While children and adolescents have a lower glycolytic capacity compared to adults, their anaerobic capacity undergoes changes with age and development. Here are key points related to anaerobic capacity in children and adolescents:

  • Limited Glycolytic Capacity: Children have a limited ability to perform anaerobic activities due to a lower glycolytic capacity. This limitation is demonstrated by several factors:
    • Muscle Glycogen Content: Muscle glycogen content in children is approximately 50% to 60% of that in adults. This lower glycogen content affects their ability to sustain high-intensity efforts.
    • Lactate Concentrations: Children do not achieve the same concentrations of lactate in muscles or blood during maximal and supramaximal exercise compared to adults. This suggests a lower glycolytic capacity in children.
    • Enzyme Activity: Children also have lower activity levels of key enzymes involved in anaerobic glycolysis, such as phosphofructokinase and lactate dehydrogenase.
  • ATP and Phosphocreatine Stores: Children’s resting stores of adenosine triphosphate (ATP) and phosphocreatine (PCr) are similar to those of adults. These energy stores are critical for short-duration, high-intensity activities lasting up to 10 to 15 seconds. Therefore, children are not compromised in activities within this time frame.
  • Anaerobic Power Output: Anaerobic mean and peak power output, as measured by tests like the Wingate anaerobic power test (a 30-second all-out maximal effort on a cycle ergometer), are lower in children compared to adults.
  • Development of Anaerobic Capacity: The development of anaerobic capacity in children and adolescents is age-dependent. It generally increases with age and growth, although the rate of increase can vary. For boys and girls aged 9 to 16, with 18 years as the criterion for 100% of the adult value, changes in anaerobic and aerobic capacity can be observed. Aerobic power is represented by V . O2max, while anaerobic power is assessed using field tests like the Margaria step-running test.
  • Gender Differences: Gender differences may also be observed in the development of anaerobic capacity. For example, aerobic fitness remains relatively constant for boys but tends to decline for girls between the ages of 12 and 16.

Endocrine Responses and Substrate Utilization During Exercise in Children and Adolescents:

Exercise has a significant impact on the endocrine system, influencing the release of metabolic regulatory hormones that mobilize carbohydrates and fats for use as fuel. These hormonal responses to exercise can also play a role in growth and development, especially in children and adolescents. Here are key points regarding endocrine responses and substrate utilization during exercise in this population:

  • Growth Hormone (GH) and Insulin-Like Growth Factor (IGF): Exercise, especially high-intensity exercise, can lead to the release of growth hormone (GH) and influence the insulin-like growth factor (IGF) axis. There has been speculation that increased GH resulting from intense exercise might contribute to increased growth during adolescence, although this hypothesis has not been definitively confirmed. Nonetheless, exercise can alter the normal daily cycling of GH, leading to peaks in GH levels in children and adolescents.
  • Insulin Response: Pediatric-focused studies indicate that the insulin response to exercise varies depending on pubertal stage and gender. Children tend to have a higher stress response to exercise, leading to differences in blood glucose control. At the beginning of exercise, children often experience relative hypoglycemia. This may be attributed to factors such as lower muscle glycogen content and an immature capacity for hepatic glycogenolysis.
  • Fuel Utilization: Children rely more heavily on fat oxidation as a fuel source during exercise, potentially due to reduced endogenous glucose production and lower muscle glycogen levels. However, their exogenous glucose oxidation rates appear to be relatively high. This profile of fuel utilization changes during puberty, with adolescents exhibiting a decreased relative rate of fat oxidation, becoming more similar to adults in this regard.
  • Impact on Body Composition: The changes in substrate utilization during exercise throughout growth and development can have implications for body composition. It may also affect nutritional requirements for optimal performance in children and adolescents.

Physiological Adaptations to Exercise Training in Children and Adolescents:

Exercise training can have a significant impact on the physiological adaptations of children and adolescents. While children are distinct from adults in various physiological aspects, they still respond positively to training programs that are tailored to their specific age groups. Here are key considerations and adaptations associated with training in children and adolescents:

  • Body Composition: Both resistance and aerobic training can lead to changes in body weight and composition in children. When participating in such training programs, boys and girls tend to experience decreases in body weight and fat mass, as well as increases in fat-free mass. However, it’s important to note that the increase in fat-free mass may be less pronounced in children compared to adolescents and adults. Additionally, high-impact weight-bearing exercises can contribute to significant bone growth beyond what is observed during normal growth.
  • Strength: Strength training can lead to improvements in muscle strength and size in children and adolescents. The growth of muscle mass and strength is influenced by factors like puberty and neural maturity. It’s important to consider the child’s developmental stage when designing strength training programs, as neural control of muscle function is limited before reaching sexual maturity.
  • Aerobic Capacity: Aerobic training can increase aerobic capacity (V . O2max) in children. However, the training-induced changes in aerobic capacity may vary depending on factors such as age and sex. Training programs should be designed to accommodate the child’s age-specific physiological characteristics.
  • Anaerobic Capacity: Children have a limited capacity for anaerobic activities due to factors like lower muscle glycogen content and glycolytic capacity. Training can improve anaerobic power and capacity to some extent, particularly in adolescents. Programs should be tailored to the child’s age, considering their metabolic capabilities.

In designing training programs for children and adolescents, it’s essential to take into account their developmental factors, including age, pubertal stage, and neural maturity. Properly structured training programs can optimize performance gains while minimizing the risk of injury. Additionally, training should be age-appropriate and aligned with the child’s individual goals and abilities.

It’s important to emphasize the need for supervision and guidance from qualified professionals, such as coaches and trainers, when implementing exercise programs for children and adolescents to ensure their safety and well-being.

Strength Training in Children and Adolescents:

The use of resistance training to enhance muscular strength and endurance in children and adolescents was once a subject of controversy and concern. There were fears that resistance training might lead to injuries and potentially stunt growth. Additionally, some scientists believed that resistance training would have minimal effects on prepubescent boys due to their low circulating androgen levels. However, recent research has led to a more widespread acceptance of resistance training as safe and beneficial for youth and adolescents.

Key points regarding strength training in children and adolescents:

  1. Safety: Research indicates that the risk of injury associated with resistance training in youth is very low. In fact, resistance training may offer some protection against injuries by strengthening muscles that support joints. Nonetheless, a cautious approach is recommended when prescribing resistance exercises for children, especially preadolescents.
  2. Effectiveness: Numerous studies have demonstrated that resistance training is highly effective in increasing strength in children and adolescents. The magnitude of strength gains is influenced by the volume and intensity of training. Percentage increases in strength for children and adolescents are similar to those observed in young adults.
  3. Mechanisms: The mechanisms underlying strength gains in children are largely similar to those in adults. However, prepubescent strength gains often occur without significant changes in muscle size and are primarily attributed to improvements in neural mechanisms. This includes enhanced motor skill coordination, increased motor unit activation, and other neurological adaptations. In adolescents, strength gains result from both neural adaptations and increases in muscle size and specific tension.
  4. Prescription: Resistance training programs for children should follow similar principles as those for adults, with an emphasis on teaching proper lifting techniques. Several professional organizations, such as the American Orthopaedic Society for Sports Medicine, the American Academy of Pediatrics, and the American College of Sports Medicine, have established guidelines for resistance training in youth. These guidelines include recommendations for the progression of resistance exercise in children.
  5. Progression: outlines basic guidelines for the progression of resistance exercise in children. These guidelines serve as a framework for developing age-appropriate and safe training programs.

Aerobic and Anaerobic Training in Children and Adolescents:

The effectiveness of aerobic training in prepubescent boys and girls to improve their cardiorespiratory systems has been a topic of controversy. Early studies suggested that training in prepubescent children did not significantly increase their V . O2max values, which measure aerobic capacity. However, these children did show improved running performance, likely due to enhanced running economy.

Key points regarding aerobic and anaerobic training in children and adolescents:

  1. Aerobic Training: While prepubescent children may not experience substantial increases in V . O2max with training, their running performance can still improve significantly. Some studies have reported small increases in aerobic capacity (about 5% to 15%) in prepubescent children, but these gains are less than those typically seen in adolescents and adults (about 15% to 25%). More substantial changes in V . O2max seem to occur after puberty, possibly due to heart growth and other factors.
  2. Anaerobic Training: Anaerobic training can enhance children’s anaerobic capacity. After training, children exhibit increased resting levels of phosphocreatine (PCr), adenosine triphosphate (ATP), and glycogen, as well as increased phosphofructokinase activity and maximal blood lactate levels. Ventilatory threshold, a marker of lactate threshold, has also been reported to increase with endurance training in 10- to 14-year-old boys.
  3. Training Principles: Standard training principles for adults can generally be applied to children and adolescents. While children can be trained similarly to adults, it is essential to consider their unique developmental stage. A conservative approach is advised to reduce the risk of injury, overtraining, and a loss of interest in sports or physical activities.
  4. Motor Skills Development: Childhood and adolescence are opportune times to focus on acquiring various motor skills. Encouraging children to explore a range of activities and sports can be beneficial for their physical and motor skill development.

Motor Ability and Sport Performance in Children and Adolescents:

Motor ability and sport performance in children and adolescents exhibit specific developmental patterns influenced by factors such as age, neuromuscular development, endocrine changes, and physical activity levels. Here are key points regarding motor ability and sport performance in this age group:

  1. Motor Ability Development: Motor ability generally improves with age during the first 17 years of life. These improvements are primarily attributed to the maturation of neuromuscular and endocrine systems, alongside increased physical activity. Notably, girls tend to reach a plateau in motor ability around the age of puberty for most assessed items.
  2. Factors Influencing Plateau in Girls: Several factors contribute to the observed plateau in motor ability among girls during puberty. First, increased estrogen concentrations and fat deposition can lead to decreased performance. Second, girls typically have less muscle mass than boys. Lastly, the trend of decreased physical activity among girls during puberty, influenced by social conditioning, plays a significant role in plateauing motor abilities. However, changing social attitudes and increased opportunities for sports and physical activity for girls are altering this trend.
  3. Sport Performance Improvement: Sport performance in children and adolescents improves in tandem with growth and maturation. Age-group records in sports like swimming and track and field demonstrate this progression. Records for anaerobic events (e.g., 100 m swim and run) and aerobic activities (e.g., 400 m swim and 1,500 m run) consistently show performance improvements with increasing age-groups.
  4. Weightlifting Records: While specific age-group records for weightlifting may not be readily available, it is assumed that weightlifting records would markedly increase during late childhood and adolescence, especially among boys. This assumption is based on normal strength gains associated with growth and development.

Special Issues in Growth and Development During Childhood and Adolescence:

As children progress through their growth and development stages from childhood to adolescence, there are specific considerations and challenges to address:

  1. Thermal Stress: Children appear to be more susceptible to heat- and cold-related illnesses or injuries in controlled laboratory settings, but this doesn’t always align with reported cases. Some key considerations regarding thermal stress in children include:
    • Children rely more on convection and radiation for heat dissipation, which is supported by greater peripheral vasodilation.
    • Their higher ratio of body surface area to mass can be an advantage for heat dissipation through radiation, convection, and conduction unless the environmental temperature exceeds skin temperature.
    • Children tend to have a lower sweating rate and slower sweat gland response to temperature changes.
    • Acclimatization to exercise in hot conditions is slower in young boys compared to adults. Limited data are available for girls.
    • Few studies have explored children’s responses to exercise in cold conditions, but they may have an advantage in conductive heat loss due to their higher surface area-to-mass ratio.

    While more research is needed, it is prudent to take a conservative approach when children engage in physical activity in extreme temperatures.

    • Regular training does not appear to impact the growth in height; children continue to grow taller at a normal rate.
    • Training can affect weight and body composition.
    • Peak height velocity (the age at which maximum growth in height occurs) and skeletal maturation rates are generally not influenced by regular training.
    • The influence of training on sexual maturation is less clear. Some data suggest potential delays in menarche (the onset of menstruation) in highly trained girls, but these findings are confounded by various factors and require further investigation.Growth and Maturation with Training: There is ongoing interest in understanding how regular physical training affects growth and maturation in children. Key observations include:
 
 
Scroll to Top