Course:KIN366/ConceptLibrary/Skeletal System

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Movement Experiences for Children
KIN 366
Instructor: Dr.Shannon S.D. Bredin
Office Hours:
Class Schedule:
Important Course Pages
Lecture Notes
Course Discussion

The skeletal system is the body system that provides a framework or boney support structure for the body. It contains all the bones, cartilages, joints and any of their associated structures. The skeleton is made up of 206 bones at the time of adulthood. There are two different classifications of the skeletal system: the axial and appendicular skeleton. The axial skeleton involves the vertebral column, skull and rib cage while the appendicular skeleton involves the limbs and extremities. The major functions of the skeletal system are support and protects other organs, acts as an attachment site for skeletal muscles, stores minerals such as calcium and phosphorus and produces different blood cell lineages (Alimohammadi & Doroudi, 2013)

Because of the many crucial functions that the skeletal system plays on the human body, it is important to acknowledge the diseases and problems associated with the skeletal system. One major disease that is detrimental to the skeletal system is osteoporosis.

Bone Development

Bones are part of a dynamic organization in which they are constantly being formed and broken down. The process of old bones being removed and replaced by new bones occurs the most during childhood and adolescence where their bones are growing in size and density. There are two processes that cause this constantly changing bone development: modelling and remodeling. Modelling involves the growth of new bone on one site and removal of old bone on a different site of the same bone while remodeling involves removal and replacement of bone on the same site. (“The Basics of Bone,” 2004). Remodeling occurs throughout life but is most dominant at the time of peak bone mass. Peak bone mass which is the point of bone’s maximum strength and density occurs normally in people’s twenties (“Kids and Their Bones,” 2012). At a certain age bone can be withdrawn at a much larger rate than deposition which can lead to problems in bone strength and women are especially susceptible to this after menopause. This is why now there is a mentality for children and adolescents to build up as much bone as they can while they can so it may last longer as they get older.

Problems in Bone Health: Osteoporosis

A very widely known and common bone disease is osteoporosis. Osteoporosis is characterized in a decrease in bone mass that is associated with an unacceptably high risk of fracture (Riggs & Melton, 1995). Low bone mass, bone thinning and weakening of bone tissue causes greater bone fragility especially in the hip, spine, wrist and shoulder. Osteoporosis can occur at any age and affects both men and women although postmenopausal women are the most susceptible to this disease. Both men and women see a start in bone reduction in their mid-30’s but as women nearing menopause, they lose bone at a rate near 2-3% a year (“Osteoporosis Facts,” 2014). Menopause causes estrogen levels, which helps keep bones healthy to decrease dramatically. Osteoporosis Canada (2014) have some facts and figures that show the significance of how harmful osteoporosis can be:

  1. 1 in 3 women and 1 in 5 men will suffer from an osteoporotic fracture.
  2. Fractures from osteoporosis are more common than heart attack, stroke and breast cancer combined.
  3. The overall yearly cost to the Canadian healthcare system of treating osteoporosis and the related fractures was over $3.9 billion in 2010.

Health Canada (2008) states that in addition to age other factors that could increase the risk of developing osteoporosis are family history, low body weight, low calcium diet, low levels of physical activity, smoking, vitamin D deficiency and excessive caffeine or alcohol intake.

Reducing Risk of Osteoporosis

Both genetics and environmental factors contribute to bone health. Although genetic disposition is not controllable, one can control environmental factors to ensure reducing the risks and effects of osteoporosis. Some preventive actions such as eat well, ensure adequate amount of calcium and vitamin D in diet, avoid smoking and excessive caffeine and alcohol, and to be active every day. As well, it would be a good idea to get a bone density test especially for the aging population particularly postmenopausal women.

Benefits of Exercise on Bone Health

As well as genetics and nutrition, exercise is very important to bone health. Exercise or physical activity has been shown to increase skeletal mass. Anderson (2000) states that there is a shown relationship between muscle mass and skeletal mass in subjects that exercised and then when put under conditions of inactivity, both skeletal and muscle tissues showed atrophy. There is a correlation between muscle mass/strength and bone mass related to the specific muscle(s). Gains in bone mass seem to be similar and benefit from the same activities as skeletal muscle mass. He also states that in recent decades there have been much more understanding of the anatomical and functional aspects muscles and bones and their relationship. The strains put on the skeletal system during exercise are sensed by mechanoreceptors, which then transduces a signal to initiate bone remodeling by guiding osteoblast activity and osteoclastic resorption (Bonnet & Ferrari, 2010). The most beneficial types of exercise for the skeletal system are weight-bearing exercises and ones that put high strain rates on the individual because as mentioned above, the skeletal system responds to strain similar to skeletal muscle and needs to have pressure. The skeletal system also has to respond to gravitational forces during weight bearing exercises. A study done by Heinonen, Oja, Kannus, Sievanen, Haapasalo, Manttari & Vuori (1995) found when comparing three female sports differencing in skeletal loading characteristics, the sports training that used high strain rates in versatile movements and high peak forces are more effective in bone formation than the training with a large number of low-force repetitions. Anderson (2000) also confirms that power and weight lifters show increases in bone mass to almost all bones of the body while tennis players only show significant increases in their dominant tennis arm. He also states that dancers, skaters, hockey players and gymnasts see gains in bone mineral content and density mostly in their legs. That proves that bone strength and density is closely related to the amount of loads and strains put on it.

Exercise and Bone Health in Children and Adolescents

Most of the time bone health is only considered an issue during adulthood and is usually overlooked during the child and adolescence years. Recently, more people have realized that skeletal system health is something that needs to be concentrated on before it’s too late later on in life. There have been an abundant amount of studies and evidence showing that exercise has positive results in the bone health of individuals especially children and adolescents. When children and adolescents are growing, there is more bone deposition than withdrawal. Their bones are growing in size and bone mass density at a great rate. Due to the increase in bone loss and fragility in older individuals, it is important for children to strengthen their skeletal system and keep it as healthy as possible to prepare for later on in life. Backrach (2001) states that because the basis of skeletal health is established at a young age, optimizing gains in bone mineral throughout childhood and adolescence is an important osteoporosis prevention tactic.

Like adults, weight-bearing activities that put strain on the skeletal system is the most effective exercise method to increase skeletal system health. Weight-bearing activities by youths were shown to have a significant influence on the gain of bone mineral density in the lumbar region of the spine (Anderson, 2000). Anderson (2000) also states that mechanical loading of proper intensity promotes an increase in skeletal mass especially during growth in the first two decades of life. As stated earlier, peak bone mass occurs during people’s twenties and because that is the point when the skeletal system is at the maximum strength and density, it makes sense that sufficient exercise in children and adolescence can positively affect their skeletal system and peak bone mass. An article written by Sifferlin (2013) states that researchers from Skane University Hospital found that children who had forty minutes of exercise a day showed higher bone density in the spine and less reported fractures than the children in the control group who did not exercise. She also reports that exercise during childhood may be related to lower fracture incidences as people age, due to their increased peak bone mass that occurs in growing children who carry out consistent physical activity. After peak bone mass, there are minimal gains compared to the huge growing rate during childhood and adolescence. An article in the New York Times written by Brody (2013) states that strong evidence shows that increasing peak bone mass in childhood by just 10 percent could delay osteoporosis by about 13 years. If true that is a huge statement because it shows how beneficial increasing peak bone mass could be for the future.

Practical Applications for Children


While any type of movement and exercise is beneficial to children’s health such as preventing obesity, but there are certain physical activities and exercise that are more favorable to increasing skeletal system health. For children to get the most gains in bone density and strength, they need to participate in weight-bearing exercises that put strain on the skeletal muscle and skeletal system. Some basic weight-bearing exercises are running, walking and jumping. But because the skeletal system responds most effectively to high strain and peak forces so constant low strain activities might not be the very best. There are some studies that even say that athletes who participate in endurance non-weight bearing activities have weaker bones and more fractures than sprinters, and ball sports athletes. The physical activities that put the best strain on bones are ones where children stop and go. Some examples of activities such as gymnastics, dancing, soccer, basketball, hockey, cross-training and lifting weights. It has to be kept in mind though that children lifting weights need to be closely monitored and watched because there are studies and evidence that say children should not be resistance training. Children should be participating in exercise daily and should not be sedentary. Children should partake in 60 minutes or more of physical activity daily (Strong, Malina, Blimkie, Daniels, Dishman, Gutin, Hergenroeder, Must, Nixon, Pivarnik, Rowland, Trost & Trudeau, 2005). It doesn’t matter whether the activities are organized or un-organized; it’s just important that they are getting the proper amount of exercise a day. Children can get the recommended amount through P.E class, sport teams, play or unorganized games, or anything else that encourages exercise.

Other Considerations

Although exercise is a major factor in promoting skeletal system health, it is important to remember it’s not the only influence. Nutrition is the other key external aspect that affects children’s bone health as well as health in general. A sufficient diet that includes adequate amounts of calcium and vitamin D should be implemented. Calcium is a mineral that is very important to bone health. Flynn (2003) states that the diet requirements of calcium are determined by the needs for bone development and maintenance with great needs during the periods of rapid growth in childhood and adolescence. Children and adolescents should also be monitored to make sure that they aren’t pressured to be aesthetically thin because if they do not eat enough to match their energy expenditure, then there might not be enough energy in the body to sustain bone health. This can lead to bone fragility and increased fractures. As well, inadequate diets and over-training can lead to female athlete triad in which one of the symptoms is loss of their menstrual cycle. The female athlete triad can be compared to menopause in that there is a loss of their menstrual cycle and similar to menopause, it negatively affects bone health.


It’s important for adults to understand the importance of bone health in children and how it can affect them presently and also in the future. All measures should be taken to increase children’s bone strength and density to decrease fracture incidences and for osteoporosis prevention when they age. For children, other than genetics, nutrition and exercise are the most important factors related to skeletal system health. Parents, coaches, teachers, or any other people that are involved with children’s care should be aware of the daily need for plenty of exercise and that even though all exercise is positive, it is the weight-bearing activities that best promote healthy bones. The best tip is to just give children and adolescence the best opportunity to move and play because their bodies and bones are already designed to respond positively to these actions.


Alexandra Sifferlin. (2013, March). Kids Who Exercise Are Less Likely to Have Fractures in Old Age. Time Healthland. Retrieved from

Alimohammadi, M., & Doroudi, M. (2013). M&M Essential Anatomy. Boston, MA: Pearson Learning Solutions.

Anderson, J.J.B. (2000). The important role of physical activity in skeletal development: how exercise may counter low calcium intake. American Journal of Clinical Nutrition, 71, 1384-1386. Retrieved from

Backrach, L.K. (2001). Acquisition of optimal bone mass in childhood and adolescence. Trends in Endocrinology & Metabolism, 12, 22-28. Retrieved from

Bonnet, N., & Ferrari, S.L. (2010). Exercise and the skeleton: How it works and what it really does. IBMS BoneKEy, 7, 235-248. doi:10.1138/20100454

Flynn, A. (2003). The role of dietary calcium in bone health. Preceedings of the Nutrition Society, 62, 851-858. Retrieved from

Heinonen, A., Oja, K., Kannus, P, Sievanen H., Haapasalo, H., Manttari, A., & Vuori, I. (1995). Bone mineral density in female athletes representing sports with different loading characteristics of the skeleton. Bone, 17, 197-203. Retrieved from

Jane E. Brody. (2013, August). To Ensure Bone Health, Start Early. The New York Times, D5. Retrieved from

Kids and their bones: A guide for parents. (2012). NIH Osteoporosis and Related Bone Diseases National Resource Center. Retrieved from

Osteoporosis Facts & Statistics. (2014). Osteoporosis Canada. Retrieved from

Riggs, B.L., & Melton, L.J. (1995). The worldwide problem of osteoporosis: Insights afforded by epidemiology. Bone, 17, 505-511. Retrieved from

Seniors and Aging – Osteoporosis. (2007). Health Canada. Retrieved from

Strong, W.B., Malina, R.M., Blimkie, C.J.R., Daniels, S.R., Dishman, R.K., Gutin, B., Hergenroeder, A.C., Must, A., Nixon, P.A., Pivarnik, J.M., Rowland, T., Trost, S., & Trudeau, F. (2005). Evidence based physical activity for school-age youth. The Journal of Pediatrics, 146, 732-737. Retrieved from

The basics of bone in health and disease. (2004). Office of the Surgeon General (US). Retrieved from