Course:KIN366/ConceptLibrary/Puberty

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Movement Experiences for Children
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KIN 366
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Instructor: Dr. Shannon S.D. Bredin
Email: shannon.bredin@ubc.ca
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Puberty is the period in an individual's life in which he or she is transitioning from a child into an adult (Sisk & Foster, 2004). During this time, there is a remarkable amount of growth in the individual in body composition, size, and shape (Rogol, Roemmich, & Clark, 2002). There is a significant increase in height, changes to body hair and, in males, even changes to the voice (Rogol et al., 2002).

The hormones involved in growth are magnified during this period, but hormone levels differ between sex (Rogol et al., 2002). With the increase in hormone levels, there are physical and emotional changes (Davies & Rose, 2000). Development of the body between sexes are distinct in the body composition, size, and shape, and also includes the development of sex characteristics (Rogol et al., 2002). There is the onset of breast development and the beginning of the menstrual cycle in females while males gain the ability to develop sperm in conjunction with ejaculatory capability (Rogol et al., 2002).

The pubertal period usually is ongoing between 2-6 years, but the length of this phase depends highly on the individual (Rogol et al., 2002).

Factors Affecting the Onset of Puberty

Although puberty occurs in all individuals eventually (Rogol et al., 2002), there are some factors that influence the timing of it.

Sex

The onset of puberty is highly dependent on whether the individual is male or female. Puberty usually has an earlier onset at the average age of 11 years old in females as compared to the average of 13 years old in males (Rogol et al., 2002). As such, females will show physically evident signs of puberty before males (Sisk & Foster, 2004). Research has been inconclusive as to what causes this onset to be earlier in females, but it is thought to be determined in the brain and is possibly genetically programmed in each individual by sex steroids (Sisk & Foster, 2004).

Exercise

Normally, exercise does not have an effect on the start of puberty if it is done in moderation. However, it has been found that excessive amounts of physical activity before the onset of puberty in childhood and adolescence inhibits growth and development. Part of this delayed growth is postponing the onset of puberty, but excessive amounts of exercise also leads to large amounts of energy and nutrients lost from the body, which results in the hindrance of growth. This is often seen in elite athletes who participate in sports like dancing, gymnastics and wrestling where weight control is crucial and energy use is high. (Rogol et al., 2002).

In females, excessive physical activity can also result in development of amenorrhea, which is the lack of a menstrual cycle, even after puberty has begun. Research shows that those who develop this condition may possibly have a lower bone mineral density when they are adults. (Rogol et al., 2002).

Disproportionate amounts of physical activity can only delay the onset of puberty. When physical activity is decreased and the body has sufficient energy and nutrients, the pubertal growth period can begin. Exercise-induced amenorrhea is also likely to subside. (Rogol et al., 2002).

Nutrition

Nutrition is one of the biggest determinants in growth and the onset of sexual development, which is why it is a significant factor in the onset of puberty. In physical growth, nutrition most highly influences muscle development, which thereby influences development of bone. (Rogol et al., 2002).

Studies have shown that in the United States, undernutrition is often a result of a self-induced food restriction or a systemic disease. Undernutrition is largely connected to the late commencement of the female menstrual cycle, as well as retards growth and development. Conversely, obesity has been shown to facilitate sex maturation at an earlier age. (Rogol et al., 2002).

Growth Changes

Sex Differences

When an individual enters the pubertal period, there are many changes that occur that have differences between sexes.

Height

Females average a height gain of 25 cm, while boys average a height gain of 28cm. (Rogol et al., 2002).

Weight

Both sexes experience a weight gain, but the onset of weight gain is earlier in males, simultaneous with the start of their height growth. In females, height begins to increase first before weight gain associated with puberty is present. (Rogol et al., 2002).

Hormones

Some are developed based on sex as they contribute to the development of sex characteristics. Androgens trigger breast development in females and the testicular growth in males, along with developments that are present in both sexes. Sexual hair grows in, a change in body odor occurs and, depending on the individual, acne begins to develop. These changes begin to occur around 1-2 years before gonadal hormones increase. (Rogol et al., 2002).

Gonadal steroid hormones are mostly testosterone in males and estradiol in females. When these hormones begin to increase, it is an indication that puberty is in its most significant stages. (Rogol et al., 2002).

Growth hormone is also a large contributor of development during puberty. It is the primary hormone in growth and its levels are heightened depending on the stage of growth in the individual. For example, when a female begins to develop breasts, the level of growth hormone in her body is higher due to the growth that is occurring at her chest. (Rogol et al., 2002).

Other Components of Body Composition

There are changes in the amount of water retained by the body during puberty. Changes to muscle, bone, and fat also occur. However, in males, muscle and bone content usually increase more than they do in females. (Rogol et al., 2002).

Muscle Development

Of course muscle development is part of the growth that occurs during puberty, but it is an area that is lacking research as it is difficult to create a procedure that properly evaluate muscle growth during puberty (Neu et al., 2001). However, it is known that muscle growth occurs before bone growth does (Rauche et al., 2003). It has also been found in Neu et al.'s (2001) study that the muscle size of the forearm increases proportional to the change in body size during the pubertal period. This could also be the case with other muscles in the body, but there is no research to confirm it. Muscle growth has been found to be dependent on changes in hormones (Neu et al., 2001).

While both males and females experience an increase in muscle size and mass, males gain a significant amount more muscle mass than females. Muscle cells double in males over the course of puberty, resulting in a greater loss of fat during that period as well. (Rogol et al., 2002).

Bone Development

Bone development is a key role in growth of the body as it influences body composition. At the end of puberty, the mass of the skeletal system will have nearly doubled. This is because approximately 90% of bone mineral is deposited as individuals transition to adulthood. (Saggese, Baroncelli, & Bertelloni, 2002).

Factors composed by Saggese et al. (2002) that affect the development of bone mass include: • Muscle mass, which regulates the thresholds for bone modelling and remodelling • Sex steroids • Growth hormone • I 25-dihydroxyvitamin D, as it stimulates retention of calcium and absorption into the bones • Insulin-like growth factors

The formation of bone is influenced by calcium. The rate at which bone modelling occurs is much higher during the pubertal period. This process is incredibly significant for bone formation and resorption as it is a major determinant in the strength of the bones in the later years of adulthood. Build up of bone mass during puberty becomes a predictor for risk of osteoporotic fracture in old age. Increased bone modelling can be stimulated by stressing the skeletal system in some form of physical activity. As bone modelling increases, the strength and the mass of the bones also improve. (Saggese et al., 2002).

Motor Development

There is no specific surge of development throughout puberty for motor skills. As children grow and develop, there is obvious improvement in motor skills as time goes by, but the pubertal period does not speed up this process. Adolescents instead develop motor skills at a greater rate before the onset of puberty, rather than during. As such, the limbs lengthen and the muscles get stronger only after motor skills have gone through their most significant changes. While it is often said that individuals move more "awkwardly" during puberty because the changes of the body are arising so rapidly, coordination is actually not impaired and the awkwardness is only a perception of others. (Davies & Rose, 2000).

As with all other aspects of puberty, there are sex differences in motor skill development that have been found. Tasks that require precise coordination are performed better by females, whereas males excel at tasks that involve throwing motions or strength. However, this seems to be the case in not just puberty, but throughout adolescent growth. (Davies & Rose, 2000).

Practical Application

Bone Health

In general, exercise is beneficial during all stages of life as it can preserve functions of daily living and lower risk of cardiovascular disease, among other benefits (Grosclaude & Ziltener, 2001). It is most impactful, however, in bone strength development at the time surrounding and during puberty (Daly, 2007). Doing high-impact weight-bearing activities before the onset puberty, during puberty, and after puberty can decrease risk of osteoporosis later in life, with the period before the onset of puberty being the most effective (Daly, 2007).

The time around and during puberty is extremely important to bone growth, and it is an age where physical activity is managed by teachers, parents, and sport coaches. As such, when planning physical activity for children in the age range of the pubertal period, high-impact weight-bearing activities should be incorporated into the plan. Bone-loading activities during regular physical activity as well as recreational play will improve bone mineral accumulation, evident in the strength of the outer layers of bones (Daly, 2007).

Participation in Sport

Sport participation is highly affected by an individual's subjective perception of how successful and competent they are in the sport (Wellard, 2006). If success is low, the individual is less inclined to continue participating in that sport, and vice versa if success is high (Wellard, 2006). After puberty, the body is bigger, bones are stronger, and muscles are more powerful (Rauch et al., 2004). Motor skills also continue to develop during this time (Davies & Rose, 2000). The outcome is a stronger body that can produce more precise movements, an advantage in most sports. Therefore, the changes that happen to the body during puberty may increase participation in sport if an individual finds that their grown body has helped him or her improve at the sport.

Conversely, body image is a large factor that affects participation in sport as well, and the developments associated with puberty produce a major change in an individual's body image. The majority of males have been shown to continue to enjoy sport after the onset of puberty and beyond, happy with their body image, but many females, on the other hand, have felt too "masculine" participating in a certain sport to continue with it following puberty. (Wellard, 2006).

The changes that occur during puberty can be overwhelming for individuals. It is important for parents and teachers to address any insecurities that may arise with puberty and can become barriers for participating in sports (Wellard, 2006). Additionally, an elite athlete can be a role model who can also encourage adolescents to remain in sports to enjoy the benefits of physical activity later in life (Adriaanse & Crosswhite, 2008). Parents and teachers can assist in finding an inspirational figure in the elite athlete world for both males and females.

References

Adriaanse, J. A., & Crosswhite, J. J. (2008). David or mia? the influence of gender on adolescent girls' choice of sport role models. Women's Studies International Forum, 31(5), 383.

Daly, R. (2007). The effect of exercise on bone mass and structural geometry during growth. Optimizing Bone Mass and Strength, 51, 33.

Davies, P., & Rose, J. (2000). Motor skills of typically developing adolescents. Physical & Occupational Therapy in Pediatrics, 20(1), 19-42.

Grosclaude, M., & Ziltener, J. (2010). Benefits of physical activity. Revue Médicale Suisse, 6(258), 1495.

Neu, C. M., Rauch, F., Rittweger, J., Manz, F., & Schoenau, E. (2002). Influence of puberty on muscle development at the forearm. American Journal of Physiology - Endocrinology and Metabolism, 283(1), 103-107.

Rauch, F., Bailey, D. A., Baxter-Jones, A., Mirwald, R., & Faulkner, R. (2004). The ‘muscle-bone unit’ during the pubertal growth spurt. Bone, 34(5), 771-775.

Rogol, A. D., Roemmich, J. N., & Clark, P. A. (2002). Growth at puberty. Journal of Adolescent Health, 31(6), 192-200.

Saggese, G., Baroncelli, G. I., & Bertelloni, S. (2002). Puberty and bone development. Best Practice & Research, Clinical Endocrinology & Metabolism, 16(1), 53.

Wellard, I. (2006). Able bodies and sport participation: Social constructions of physical ability for gendered and sexually identified bodies. Sport, Education and Society, 11(2), 105-119.