Strength Training for Children and Adolescents

This essay will particular focus on the links between a child development and training load by critically discussing, bone development, muscle mass and strength, menstruation in young females, issues of obesity and physical inactivity, aerobic and anaerobic exercise, and injury. After highlighting the contemporary research surrounding these links, the findings and methodology are evaluated. To begin, a brief definition of training load is put forward. The findings founds within training load and children may not be a as straight forward as it appears as much research has looked at the link between training load and a child’s development, through peered reviewed research. The ways of assessing physical activity training load and development, as well as the reasoning why they should and should not take part in exercise, with reference to bone and muscle changes. Also the implications to menstruation in young female athletes and which exercise type of exercise is better for the young. As well as the negative issues relating to injury during physical activity, with reference to the potential affects in to adulthood. Physical activity and health is also known to be beneficial, however the methods and ways in which this is done may give different results. This will be discussed through how physical activity can improve the quality of life and also how being inactive can have issues. It will be looked at through many health conditions including cardiovascular diseases, hypertension, osteoporosis, cancers, and obesity, and also how physical activity can reduce the chance of getting some of these health conditions.

It must firstly be mentioned what training load is. Training load is the amount of exercise completed and how much energy used (Rowland, 2005). Children and adolescents have taken part in physical activity through school in physical education classes, but there are those who enjoy exercise more than others. In each case there are physiological implications which can occur, such as developmental issue which can include, bone and muscle problems, injury and health issues such as heart disease, cancers and obesity, as well as menstrual complications in females. Also there are implications for children and adolescents who do not exercise. As children progress into adolescence, the influence of peers and peer pressure becomes noticeable and a widespread decline in physical activity becomes more of a problem. Generally boys will tend to participate in some sort of exercise or sport with friends at a higher intensity than girls (Sallis, 1993). Rowland (2007) suggested that physical activity has many benefits for the young, as it promotes health, thus making you healthy in adult life. However Rowland goes on to mention that more research is needed to look at factors such as frequency and duration of physical activity during childhood as this can determine how reliable the health outcomes maybe in adulthood. Furthermore it was suggested that in the long term that if adolescents are physical active it will enhance bone health and reduce certain cancers such as breast cancer. However Twisk (2001) discussed the onset of many chronic illnesses which start at child and that strategy should be put in to plan to reduce disease early on in life. Exercise found that one important way to stop the on set of disease, but increasing physical during childhood and adolescence. Evidence found that exercise guidelines for children and adolescents is weak, and additional it was found that only a small amount of research which found that exercising when young can be related to health in adulthood. This can suggest that guidelines based on the public, should be more focused on health benefits, rather than how much exercise should be completed on a daily basis.

Behm, Faigenbaum and Klentrou, (2008) produced a review on the recommendations of resistance training on paediatrics, with the correct training methods can be safe and improve health. Studies measuring (anthropometric) children have not found to show an increase in muscular hypertrophy with resistance training in paediatrics with cystic fibrosis and cerebral palsy. Surprisingly it has been mentioned that there is no minimum age to start resistance training in children, however this does need to be structured when exercising. The resistance training in children needs to be with a qualified instruction and while being supervised. This seems in many cases to be unachievable as not every child can have instruction with exercising (e.g. a child running is exercise but does not need instruction or supervision), never the less resistance training exercise can aid in muscle strength, endurance, balance, power and co-ordination and many health benefits. Moderate stress on bones (e.g. weight-bearing exercise) builds a stronger skeleton. Heavy loads or extreme forces can retard bone growth. Therefore, power and heavy weight training should be avoided until later stages of development. Training should be closely monitored during adolescence for signs of stress / overuse. Bones are more susceptible to fractures when growth plates (cartilage sights that are not yet ossified) are still present. If bone growth accelerates faster than muscle length, then undue stress can be placed on the skeleton during growth spurts; this can be exasperated by repetitive exercises or movements. Burrows (2007) found that diseases such as osteoporosis are becoming increasingly high, however weight-bearing exercise is a good way to enhance bone mineral density, making it stronger, if this exercise is continued throughout the growth period. It has been suggested that sport needs to start at perpubertal age to obtain peak bone mass. Sports such as gymnastics and football are recommended to increase peak bone mass. Within this research area there also seems to many authors suggesting that training load will be good for muscle and bone strength, especially weight bearing training as this strengthen the body, additional some authors have mentioned professional support and instruction in training will stop the chances of getting injury, but surely injury will be enviable, as it is the individual who is doing that specific exercise or sport can have an accident.

Despite this there are other issues with training load on the young, especially in females and menstruation, as Eliakim & Beyth, (2003) study found when looking at exercise training, menstrual irregularities and bone development in children and adolescents. Weight bearing exercise has been know to be important in bone development, this is even more important in children and adolescents, as bone mineral density reaches around 90% of its peak by the second decade. Physical activity in childhood and adolescence can reduce the risk on bone disease such as osteoporosis in later life. However strenuous exercise in females can affect there reproductive system causing athletic amenorrhea (this is the stopping of menstruation for six months or more). This is becoming more popular as it is 4-20 times higher than the general populations, especially in the female athlete. This can lead to skeletal fractures, unstable spine and vertebral joints, as well as menstrual abnormalities. As a result female athletes would have to reduce training, to reduce skeletal affects, as this is more harmful to bones growth, especially if a child or adolescence is still at the rapid growth stage at this time and prevent changes in menstruation.

Further issues relating to adolescents and training load are growth, maturation and strength. Bernadette (2006) study looked at whether moderate-high amounts of dance training would influence linear growth and sexual maturation if girl ages 8-11 years old, through puberty. Results found that no change of height velocity of the dancers in year one. However when controlling the groups for maturations, fat mass, lean mass and also extracurricular activities (not dancing), there where found to be no changes in growth or velocity growth in height, sitting height or leg length. Thus finding that there was link between age at menarche and hours and years of dance training. Also resulting in no affect occurring in moderate high level of dance training in linear growth or maturation. However it has been found that preadolescent boys and girls can see meaningful gains in strength with proper training. Although it has been documented that adults and adolescents can achieve significant improvements with strength training, training gains for children have been questioned. The argument that led to the false belief that children couldn’t benefit from training was based on two presumptions. First, it was considered unlikely that notable changes in muscular strength and endurance could occur prior to puberty, due to lower levels of circulating androgens (e.g., testosterone). The underlying assumption was that higher levels of androgens were necessary for improvements in muscle size and strength to occur. Second, children naturally become stronger as they grow, and strength gains beyond that were thought improbable. Previous studies, which seemed to support this, were often limited in study design and research methodology (such as low intensity, low volume or short duration training protocols). Nevertheless, this data seemed to suggest that resistance training was ineffective in the very young population. Faigenbaum (2000)

A growing body of scientific evidence in support of children’s strength training has arisen within the past decade. The literature provides strong documentation that both male and female preadolescents can improve strength significantly with well-designed resistance-training programs. Recent reviews analyze the available research by comparison. Although a relatively small number of studies were included, one review revealed that a majority of studies demonstrated strength gains between 13 and 30 percent as a result of training (Falk & Tenenbaum, 1996). Another reported similar results for children and youth, and each of the studies included in this review indicated that resistance training was generally effective, regardless of participants or study characteristics (Payne, Morrow, Johnson & Dalton, 1997). Gains from strength training for preadolescents are generally attributed to neural adaptations and motor learning, rather than circulating androgens. Muscle hypertrophy, or an increase in the cross-sectional area of a muscle, is not usually detected in children as a result of training. Since muscle size has been correlated with strength, studies indicating no increase in muscle hypertrophy implied that strength training was ineffective in younger participants.

On the opposite side of the scale there are those children and adolescence who do not exercise. It is well known that obesity is one of the biggest health problems across the world, but with children becoming less physical active this will be inevitable, along with several other major diseases which can include coronary heart disease, hypertension, osteoporosis, diabetes mellitus, lung disease and some cancers. Watts, Jones, Davis & Green (2005) study found evidence that non physically active children are most like to become less physically active in adulthood, furthermore it is encouraged that physical activity habits in children help patterns of exercise in adulthood. Random control trails have been designed to look at exercise training in both children and adolescence. The studies found exercise does have beneficial outcomes, but it does always reduce bodyweight, it does however have more beneficial effects to changes in fat and lean body mass, thus showing the need for better assessment in future exercising training studies. Exercise can improve cardiovascular fitness and muscle strength, but little affect on blood lipids and blood pressure in obese youths. Similar important studies have found that exercise improves vascular endothelial function, which was found to be a substitute measure to predict the atherosclerotic risk in children and adolescents who are obese (Celermajer, Sorensen & Gooch, 1992).Training studies have found an improvement in vascular function, however an absence in changes in lipid fractions, haemodynamic variables or glucose metabolism as exercise appears to have a beneficial effect on the vasculature (Watts, Beye & Siafarikas et al, 2004)

Another area which is essential in a children development is the aerobic and anaerobic development in children and adolescence. Cardiovascular function being in childhood but is also different of those of an adult. Children have smaller heart chambers and lower volume than adults, thus finding a lower stroke volume than an adult during rest and exercise. Children have a smaller stroke volume, but a child has a higher maximal heart rate compared to an adult. An adolescent, max heart could be found to be higher than an adult but not quiet as high as a child’s (Sharp, 1995). Although higher heart rates can not be compensated for a child’s lower stroke volume and there’s a child’s cardiac output is lower than in adults (Wilmore & Costill, 1994). Thus suggesting that more of the cardiac output goes to working the muscle in children than it would in adults (Wilmore & Costill, 1994). Children are found to be more naturally aerobic, rather than anaerobic, but unfortunately there are few studies which have found that aerobic capacity in children will improve with training aerobically. Furthermore Rowlands (1992) argued that no study’s have been complied which has the specific outline of 12 weeks training, over three days per week, with heart rates of 160 beats per minute over twenty minutes as a minimum requirement, as well as a large group of participants, with a control, thus being similar to an adults training schedule. Rowland found that if children complete a similar aerobic training routine and intensity to an adult, they would improve there V02 max between 7 and 26%. Which suggests children can improve aerobic fitness from an adult training program. Sharp (1995) found that children have a lower lactate production and the anaerobic threshold in children give heart rates of between 165-170 beat per minute, which is similar to a trained endurance adult. Yet sedentary adult’s anaerobic threshold is between 120-150 beats per minute. Which means that heart rate will be higher in a sedentary child than an adult. More evidence has supported high intensity stimulus theory that activity level in children is not related to V02 max (Rowland, 1992). As children are not as active as they once were, Armstrong & Welsman (1994) stated that they are still aerobically fit, which suggest children are naturally fit. Thus, to improve a child’s natural fitness, a good, strong training program is needed.

Whether children exercise aerobically or anaerobic, there is the issue of heat conditions, also know as thermoregulation. Falk (2008) found that children produce more heat per kilogramme body weight than adults, but their thermoregulatory system is not as good. This is partly because they sweat less. For example, a 12-year-old boy may sweat 400ml per square meter of skin per hour, compared to an adult man’s 800ml. Girls and women sweat proportionately the same, although less in absolute quantity terms. Children also tend to have higher skin temperatures, which hinder the flow of heat from body core to the periphery. However, children have a proportionately greater skin surface area the smaller they are. A young adult weighing 64kg will have a surface area of about 1.80 square meters; an eight year- old weighing 25kg will have a skin area of 0.95 square meters, i.e. 36 per cent more surface area per unit of weight. This helps to correct thermal imbalances, but can be a disadvantage when running in direct sun (or swimming in cold water) – with the possibility of a faster rate of overheating (or overcooling).

Injury is another common occurrence in children who take part in sport and exercise during there development. Adirim (2003) found that within the US around 30 million children take part in sport and exercise, and many of those have an injuries, which is due to overuse, also of those injuries over one third where of school age. With the physical and physiological differences of children and adults, this is one reason why children are more susceptible to injury. Overuse injuries are common, overuse injuries occur from the repetitive application of submaximal stresses to otherwise normal tissues. (Outerbridge & Micheli, 1995) Injuries which are the most common are the ankle and knee. Overtraining and exposure to excessive levels of physical activity can cause an increased chance of injury, overuse injuries can affect normal physical growth and maturation. Prevention is the key, gradual rather than sudden increases in stresses and intensity can usually avoid physical breakdown. Early changes of the training program can ensure successful return to sport.

In conclusion, it can be found after looking through peered reviewed research that training load can have both positive and negative aspects. In research it has found that Moderate stress on bones builds a stronger skeleton. Furthermore heavy loads or extreme forces can retard bone growth. Thus, power and heavy weight training should be avoided until later stages of development. Training load and menstruation in female athletes can have detrimental affects on reproductive development. As a result female athletes would have to reduce training, to reduce skeletal affects, as this is more harmful to bones growth, especially if a child or adolescence is still at the rapid growth stage at this time and prevent changes in menstruation. Surprisingly children are becoming more susceptible to many more health conditions as a result of falling physical activity levels, even when knowing that exercise can improve cardiovascular fitness and muscle strength, but little affect on blood lipids and blood pressure in obese youths. Although it has been found that children are most aerobically fit rather than anaerobic, but unfortunately there are few studies which have found that aerobic capacity in children will improve with training aerobically. Children also have a lower lactate production and the anaerobic threshold in children give heart rates which are similar to a trained endurance adult. Furthermore thermoregulation in children produce more heat than adults, but their thermoregulatory system is not as good. However to correct thermal imbalances, but can be a disadvantage when running in direct sun, with the possibility of a faster rate of overheating or overcooling. Finally injury is another aspect which occurs during a child’s development, when taking part in sport and exercise. The most common injuries are overuse (joints commonly affected are ankle and knee). Children are most susceptible to injury during development as they are not coordinated and react slower than adults. It’s also been found that instructions in training will stop the chances of getting injury.

References
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Celermajer DS, Sorensen KE, Gooch VM, et al. Non-invasive detection of endothelial dysfunction in children and adults at risk of atherosclerosis. Lancet 1992; 340: 1111-5
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