skeletal adaptation in young gymnasts Abstract: This article discusses how participation in recreational gymnastics can improve the skeletal health of young girls in terms of gaining bone mass, strength, and density. Additionally, the article investigates negative skeletal adaptations, such as overuse injuries and the effects of rigorous training on growth and maturity. By Alexa Knorr, BSN, MSN, RN, CPNP
ymnastics requires the body to withstand unique forces that it would not otherwise naturally sustain. In artistic gymnastics, participants train in four different events (uneven bars, floor exercise, beam, and vault), each applying a different type of mechanical loading to the body that may far exceed the gymnast’s body weight.1,2 Rigorous training and repetition of new skills are essential in this sport and can ultimately lead to both skeletal advantages and disadvantages in developing female gymnasts. This article will discuss these potential skeletal adaptations to give nurse practitioners (NPs) insight into how gymnastics can enhance the development of healthy bones in young girls while also cautioning NPs to remain
G
vigilant for signs and symptoms of excessive training, which may lead to injury. There is general consensus that weight-bearing exercise in childhood has significant and lasting benefits to the developing skeleton.3-5 However, repeated exposure to forces applied to the body when bending, swinging, and tumbling, requires the skeletons of gymnasts to adapt appropriately to maintain control. The skeleton is able to adapt because bone can reconstruct and modify its makeup in response to the different forces and loading it experiences. Bone is particularly sensitive to adaptation during adolescence because this period of development coincides with the skeleton’s greatest bone mass growth velocity.6
Keywords: bone adaptation, bone density, bone geometry, forearm, growth, gymnastics, mechanical loading, overuse injury, pediatrics, pubertal development, spondylolisthesis, spondylolysis
38 The Nurse Practitioner • Vol. 39, No. 5
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
www.tnpj.com
Photo by Gustoimages / Science Source ©
Positive and negative
Positive and negative skeletal adaptation in young gymnasts
Positive skeletal adaptation in gymnasts includes increased densitometric and geometric structures in the upper extremities, which likely protect against common childhood fractures and later, osteoporosis. These positive skeletal benefits are not solely reserved for elite gymnasts who practice upwards of 25 hours per week, since increased bone density and size can be achieved from gymnastics at the recreational level (training less than 10 hours per week). Although participation in gymnastics can have several lasting benefits to young girls’ developing skeletons, the extensive training time and intensity required to advance in the world of elite gymnastics can leave a skeletally immature gymnast at risk for injury. These maladaptations typically present as overuse injuries in the form of physeal injuries, spondylolysis, and resulting spondylolisthesis. ■ Upper extremity adaptation Skeletal benefits for recreational gymnasts are localized to the upper distal extremities.7-12 This finding is not particularly surprising considering that gymnasts repeatedly practice skills and exercises in an inverted position, causing them to bear a considerable amount of weight on their wrists. Research has shown that gymnasts experience no greater bone strength or size in their lower extremities than nongymnasts. For example, Tournis et al. failed to find a difference in tibial bone mineral density when comparing gymnasts and nongymnasts.13 This is likely due to the probability that many nongymnasts participate in physical activity involving weight-bearing, jumping, and compression exercises of the lower legs, making changes in bone parameters between gymnasts and nongymnasts less apparent in the lower extremities than the upper extremities.14-16 Greene and Wiebe also did not find differences in bone adaptation of the lower extremities after repeated simulation of droplandings.17 Though this study did not include gymnasts, the inconclusive results may demonstrate that the femur is less sensitive to adaptation due to its weight-bearing function in everyday life.17 ■ Radial bone adaptation Several studies have found increased bone mineral density and size in the distal radius using quantitative peripheral computed tomography to assess forearm bone adaptation to mechanical loading. 2,7,8,10-12,14 However, while bone strength and size were greater in recreational gymnasts at the distal radial site, gymnasts participating in more intense training showed increased density at both the distal and proximal areas of the radius.7 This indicates that bone mass accrual and strength are positively correlated to the amount and intensity of exercise. A longitudinal study further www.tnpj.com
supports this conclusion by investigating bone parameter adaptation in recreational gymnasts. The researchers found no significant differences in skeletal benefits until after year 3 of gymnastics participation.11 Bone parameter measurements differed at various sites along the radius, suggesting that different types of mechanical loading cause different effects at specific locations on the bone (see Radial adaptation). Specifically, the radial epiphysis was shown to increase mainly in density, whereas the shaft of the bone primarily gained geometric benefits with an increased cross-sectional area.8,9 These findings illustrate how the dynamic forces that gymnasts experience can elicit sitespecific bone changes. For example, increased density at the distal radius is likely due to repetitive compression forces, and increased bone shaft size is an adaptation to bending forces. Even though there were significant differences in skeletal benefits found between sites of the radial bone, less dramatic skeletal benefits were found in the diaphysis when compared with the epiphysis.9,11 Burt et al. compared bone adaptation among three groups of gymnasts with different levels of training and found that both the low-level and high-level groups had increased epiphysis bone density, while only the high-level gymnast group had increased diaphysis size.7 In addition, Ducher et al. found that retired elite gymnasts maintained their bone benefits years after ceasing gymnastics activity.14 Again, these earlier and longerlasting changes in the radial epiphysis may indicate that positive bone adaptation may be dose-dependent and that bone shaft adaptation may not start until after more rigorous gymnastics training. ■ Ulnar bone adaptation While most research on skeletal adaptation of gymnasts has been focused on radial bone parameters, Burt et al. and Ducher et al. contend that the ulna should also be considered when studying the acquired skeletal benefits of recreational gymnastics participation.8,14 While both studies found increased bone parameters in both the radius and ulna in gymnasts, the researchers made an important discovery when uncovering how structural changes specific to the ulna occur differently than they do in the radius (see Ulnar adaptation). As discussed, the radial bone of gymnasts generally shows the greatest adaptation at the epiphysis, and interestingly, the ulna demonstrates greatest adaptation at the diaphysis. While the radius has also shown increases in size at the diaphysis, comparatively, the bone shaft of the ulna exhibits an even greater size increase at the same site.8,14 Furthermore, opposite to radial adaptation patterns, the epiphysis of the ulna shows less bone mineral accrual than the epiphysis of the radius. These findings may be explained The Nurse Practitioner • May 2014 39
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Positive and negative skeletal adaptation in young gymnasts
Radial adaptation7-11,14 Age of subjects
Goal of research
Hours training
Results
Burt, Naughton, Greene, Courteix, and Ducher, 2011 6-11 years
Comparing bone adaptation in recreational gymnasts and nongymnasts
Recreational gymnasts were assigned to three categories: High-training gymnasts: 6-16 hours/week Low-training gymnasts: 1-5 hours/week Nongymnasts:
ymnastics requires the body to withstand unique forces that it would not otherwise naturally sustain. In artistic gymnastics, participants train in four different events (uneven bars, floor exercise, beam, and vault), each applying a different type of mechanical loading to the body that may far exceed the gymnast’s body weight.1,2 Rigorous training and repetition of new skills are essential in this sport and can ultimately lead to both skeletal advantages and disadvantages in developing female gymnasts. This article will discuss these potential skeletal adaptations to give nurse practitioners (NPs) insight into how gymnastics can enhance the development of healthy bones in young girls while also cautioning NPs to remain
G
vigilant for signs and symptoms of excessive training, which may lead to injury. There is general consensus that weight-bearing exercise in childhood has significant and lasting benefits to the developing skeleton.3-5 However, repeated exposure to forces applied to the body when bending, swinging, and tumbling, requires the skeletons of gymnasts to adapt appropriately to maintain control. The skeleton is able to adapt because bone can reconstruct and modify its makeup in response to the different forces and loading it experiences. Bone is particularly sensitive to adaptation during adolescence because this period of development coincides with the skeleton’s greatest bone mass growth velocity.6
Keywords: bone adaptation, bone density, bone geometry, forearm, growth, gymnastics, mechanical loading, overuse injury, pediatrics, pubertal development, spondylolisthesis, spondylolysis
38 The Nurse Practitioner • Vol. 39, No. 5
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
www.tnpj.com
Photo by Gustoimages / Science Source ©
Positive and negative
Positive and negative skeletal adaptation in young gymnasts
Positive skeletal adaptation in gymnasts includes increased densitometric and geometric structures in the upper extremities, which likely protect against common childhood fractures and later, osteoporosis. These positive skeletal benefits are not solely reserved for elite gymnasts who practice upwards of 25 hours per week, since increased bone density and size can be achieved from gymnastics at the recreational level (training less than 10 hours per week). Although participation in gymnastics can have several lasting benefits to young girls’ developing skeletons, the extensive training time and intensity required to advance in the world of elite gymnastics can leave a skeletally immature gymnast at risk for injury. These maladaptations typically present as overuse injuries in the form of physeal injuries, spondylolysis, and resulting spondylolisthesis. ■ Upper extremity adaptation Skeletal benefits for recreational gymnasts are localized to the upper distal extremities.7-12 This finding is not particularly surprising considering that gymnasts repeatedly practice skills and exercises in an inverted position, causing them to bear a considerable amount of weight on their wrists. Research has shown that gymnasts experience no greater bone strength or size in their lower extremities than nongymnasts. For example, Tournis et al. failed to find a difference in tibial bone mineral density when comparing gymnasts and nongymnasts.13 This is likely due to the probability that many nongymnasts participate in physical activity involving weight-bearing, jumping, and compression exercises of the lower legs, making changes in bone parameters between gymnasts and nongymnasts less apparent in the lower extremities than the upper extremities.14-16 Greene and Wiebe also did not find differences in bone adaptation of the lower extremities after repeated simulation of droplandings.17 Though this study did not include gymnasts, the inconclusive results may demonstrate that the femur is less sensitive to adaptation due to its weight-bearing function in everyday life.17 ■ Radial bone adaptation Several studies have found increased bone mineral density and size in the distal radius using quantitative peripheral computed tomography to assess forearm bone adaptation to mechanical loading. 2,7,8,10-12,14 However, while bone strength and size were greater in recreational gymnasts at the distal radial site, gymnasts participating in more intense training showed increased density at both the distal and proximal areas of the radius.7 This indicates that bone mass accrual and strength are positively correlated to the amount and intensity of exercise. A longitudinal study further www.tnpj.com
supports this conclusion by investigating bone parameter adaptation in recreational gymnasts. The researchers found no significant differences in skeletal benefits until after year 3 of gymnastics participation.11 Bone parameter measurements differed at various sites along the radius, suggesting that different types of mechanical loading cause different effects at specific locations on the bone (see Radial adaptation). Specifically, the radial epiphysis was shown to increase mainly in density, whereas the shaft of the bone primarily gained geometric benefits with an increased cross-sectional area.8,9 These findings illustrate how the dynamic forces that gymnasts experience can elicit sitespecific bone changes. For example, increased density at the distal radius is likely due to repetitive compression forces, and increased bone shaft size is an adaptation to bending forces. Even though there were significant differences in skeletal benefits found between sites of the radial bone, less dramatic skeletal benefits were found in the diaphysis when compared with the epiphysis.9,11 Burt et al. compared bone adaptation among three groups of gymnasts with different levels of training and found that both the low-level and high-level groups had increased epiphysis bone density, while only the high-level gymnast group had increased diaphysis size.7 In addition, Ducher et al. found that retired elite gymnasts maintained their bone benefits years after ceasing gymnastics activity.14 Again, these earlier and longerlasting changes in the radial epiphysis may indicate that positive bone adaptation may be dose-dependent and that bone shaft adaptation may not start until after more rigorous gymnastics training. ■ Ulnar bone adaptation While most research on skeletal adaptation of gymnasts has been focused on radial bone parameters, Burt et al. and Ducher et al. contend that the ulna should also be considered when studying the acquired skeletal benefits of recreational gymnastics participation.8,14 While both studies found increased bone parameters in both the radius and ulna in gymnasts, the researchers made an important discovery when uncovering how structural changes specific to the ulna occur differently than they do in the radius (see Ulnar adaptation). As discussed, the radial bone of gymnasts generally shows the greatest adaptation at the epiphysis, and interestingly, the ulna demonstrates greatest adaptation at the diaphysis. While the radius has also shown increases in size at the diaphysis, comparatively, the bone shaft of the ulna exhibits an even greater size increase at the same site.8,14 Furthermore, opposite to radial adaptation patterns, the epiphysis of the ulna shows less bone mineral accrual than the epiphysis of the radius. These findings may be explained The Nurse Practitioner • May 2014 39
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Positive and negative skeletal adaptation in young gymnasts
Radial adaptation7-11,14 Age of subjects
Goal of research
Hours training
Results
Burt, Naughton, Greene, Courteix, and Ducher, 2011 6-11 years
Comparing bone adaptation in recreational gymnasts and nongymnasts
Recreational gymnasts were assigned to three categories: High-training gymnasts: 6-16 hours/week Low-training gymnasts: 1-5 hours/week Nongymnasts:
