Anatomical & Physiological Changes: Children, Adolescents, Adults & Seniors

Throughout one's lifetime, the body goes through several anatomical and physiological changes. This event is due to the evolution of several systems in our body, some of which include the skeletal, muscular, integumentary, respiratory and regulatory systems. These changes can lead to barriers impacting exercise and overall activity (Williamson, 2019). However, the correct approach to an exercise plan can help a child, adolescent, adult, and/or senior, exercise efficiently and safely.

Anatomical and physiological differences between youth and adult population

I. Growth & Development

Every child and adolescent has bones, joints, and muscles that grow at a rapid rate (Williamson, 2019). An epiphyseal growth plate acts as a layer of protection and is the main site for the longitudinal growth of long bones (Pines & Hurwitz, 1991). The bones, joints, and muscles continue to grow in size, in response to several hormonal changes happening in the body. This event can be an uncomfortable process for many children and adolescents, causing physical discomfort, and a decline in psychosocial health. Compared to the adult population, these significant changes can result in several barriers to exercise that cause long term effects. First, neuromuscular control develops over time,  as motor neurons and muscle fibers learn to communicate better. However, during this process, balance and coordination can be hard to achieve (Williamson, 2019). Approximately 6% of children are diagnosed with developmental coordination disorder, affecting the development of their motor functions, leading to lack of balance, falls and coordination (Fong et al., 2016).

There is also concern for an increased risk of musculoskeletal injury, due to epiphyseal plate damage and intervertebral disc rupture (Williamson, 2019). Many times, this has been related to improper form during heavy loads in bouts of resistance training. It’s essential that resistance training is properly monitored and prescribed. The correct exercise type, load, set, and repetition will enhance a child's growth period, without causing growth plate injuries. A proper resistance training program can improve lipid profiles, fat free mass, balance, bone density and self esteem in children and adolescents (Dehab and McCambridge, 2009).

II. Response to exercise

A child's energy expenditure is much higher during endurance activities. They require 20-30% more oxygen per unit of body mass while running or jogging. A higher respiratory frequency caused by a shorter respiratory cycle causes less efficient respiration, compared to adults. They also have a lower stroke volume, lower cardiac output and higher heart rate (Williamson, 2019). Hence, when training children, the typical formula (220-age) for finding maximum heart rate is not an accurate representation. Instead, when training those under 16, a target heart rate is typically around 170-180 bpm (Williamson, 2019). Also, a child's integumentary system functions differently from an adult, making their sweat rate less efficient. Children produce more heat than adults, but have underdeveloped sweat glands. Hence, during physical activity, they can overheat much faster than adults can (Williamson, 2019). Exercise professionals must monitor their water and electrolyte intake. Clark et al. (2014) recommends a longer warmup and cooldown to avoid overheating. They also state to limit workouts to under 30 minutes in hot and humid environments (Clark et al., 2014).

Anatomical and Physiological differences between the senior population and the adult population

As we age, there are several changes that occur in our body that can make daily activities and exercise more difficult. One's biological age is determined by several factors. While habits such as tobacco use, high stress levels, and obesity can negatively affect our biological age, physical activity is the most influential factor in reducing negative changes that coincide with getting older (Williamson, 2019). Bodies naturally go through apoptosis, where the body's cells begin to die. However, they are then replaced with newer cells. As we get older, the loss of cells can outpace the replacement of newer cells, which results in lack of efficiency over time. Analogous to children, a side effect of this is the inability to control core body temperature. The number of capillaries and sweat glands decline over time, and interferes with their ability to evaporate sweat (Williamson, 2019). Larose et al. (2014) performed a study to determine age related differences in heat loss. They analyzed sixty men in five different age groups. In dry humid conditions, the groups of ages 40-85 years of age produced 13-38% more heat than the 20-30 year old group (Larose et al., 2014). Hence, exercise professionals need to monitor the room's temperature and comfort levels of their senior exerciser.

Senior regulatory systems are significantly affected with age. They can experience a loss of neurons, neurotransmitters, blood flow to the central nervous system and several hormonal level decreases. There also appears to be a correlation between the endocrine system and the muscular and skeletal system. Williamson, (2019) states that the pituitary gland reduces its amount of human growth hormone with age. In return, this affects the strength of skeletal muscles. Gupta & Kumar (2022) states that a decline in hormones such as testosterone, estrogen, insulin-like growth factor (IGF-1), and dehydroepiandrosterone can lead to sarcopenia. They continue to demonstrate that a reduction in these hormones is linked to the occurrence of sarcopenia, which proves that sarcopenia is a result of endocrine failure (Gupta & Kumar, 2022). The article highlights how exercise is crucial in preventing the effects of sarcopenia. Exercise can enhance our immune system, cardiovascular system, and increase muscle strength, and endurance. Muscular force generation and overall physical performance are improved by muscle protein synthesis and muscle fiber growth (Gupta & Kumar, 2022; Williamson, 2019). We can also see this correlation with osteoporosis, which is the condition where old bone breaks down at a faster rate than new bone being developed. In women, bone mass decreases with age, largely due to the loss of estrogen (Williamson, 2019). Also, the skeletal system goes through various changes hindering a seniors mobility, flexibility, coordination and overall range of motion. As humans get older, articular cartilage begins to wear away, collagen fibers shorten and synovial joint fluid is reduced. These side effects can lead to sprains, bursitis, and arthritis (Williamson, 2019). An article from Backer et al., 2020 discusses basal arthritis, which is arthritis of the thumb. This type of arthritis originates at the base of the thumb where the metacarpal bone meets the trapezium bone in the wrist. Basal arthritis causes extreme discomfort and pain, making it hard for sufferers to do everyday activities, such as buttoning a shirt, opening a jar, or gripping a pen to write (Bäcker et al., 2020).

References

Bäcker, H. C., Freibott, C. E., Rizzo, M., Lee, D. H., Glickel, S. Z., Strauch, R. J., & Rosenwasser, M. P. (2020). Thumb disability examination (TDX) as a new reliable tool for basal joint arthritis. Journal of wrist surgery, 9(3), 209–213. https://doi.org/10.1055/s-0040-1701510

Clark, M., Sutton, B. G., Lucett, S., & National Academy of Sports Medicine. (2014). 

NASM Essentials of Personal Fitness Training. Jones & Bartlett Learning.

Dahab, K. S., & McCambridge, T. M. (2009). Strength training in children and adolescents: raising the bar for young athletes?. Sports health, 1(3), 223–226. https://doi.org/10.1177/1941738109334215

Fong, S. S. M., Guo, X., Cheng, Y. T. Y., Liu, K. P. Y., Tsang, W. W. N., Yam, T. T. T., Chung, L. M. Y., & Macfarlane, D. J. (2016). A novel balance training program for children with developmental coordination disorder: A Randomized Controlled Trial. Medicine, 95(16), e3492. https://doi.org/10.1097/MD.0000000000003492

Gupta, P., & Kumar, S. (2022). Sarcopenia and endocrine ageing: Are they related?. Cureus, 14(9), e28787. https://doi.org/10.7759/cureus.28787

Larose, J., Boulay, P., Wright-Beatty, H. E., Sigal, R. J., Hardcastle, S., & Kenny, G. P. (2014). Age-related differences in heat loss capacity occur under both dry and humid heat stress conditions. Journal of applied physiology (Bethesda, Md. : 1985), 117(1), 69–79. https://doi.org/10.1152/japplphysiol.00123.2014

Pines, M., & Hurwitz, S. (1991). The role of the growth plate in longitudinal bone growth. Poultry science, 70(8), 1806–1814. https://doi.org/10.3382/ps.0701806

Williamson, P. (2019). Exercise for special populations. Wolters Kluwer.