Osteoporosis, through its association with age-related fracture, is a major public health concern worldwide. Although osteoporosis was once considered a disease of the elderly, it is now recognized as a condition that has childhood antecedents. The capacity of bone to adapt is the greatest before puberty because of a higher rate of modeling and remodeling. Therefore, the amount of bone gained during childhood and adolescence has the potential to impact lifetime skeletal health. Children who participate in greater amounts of physical activity have greater bone mineral accrual in adolescence as well as a greater peak bone mass in young adulthood. Structured impact loading during growth also positively influences bone parameters. However, the intensity, duration and frequency of loading that is required to elicit skeletal benefits are not well established. Furthermore, although structured physical activity during growth has been hypothesized to delay or prevent the risk of osteoporosis and related fracture later in life there is no clear evidence of a persisting benefit once the loading stimulus has been removed. Therefore, the objective of this thesis was to investigate low-level impact loading during growth and skeletal development as well as to determine the influence of the withdrawal of the loading stimulus on adult bone parameters. Two studies were necessary to realize this objective. The findings should help to determine whether adolescent and adult bone health benefits from structured physical activity during growth. If this is found to be the case then structured gymnastic activity could be promoted as an effective means to optimize adult bone mass, structure and estimated strength.<p> Study 1: The purpose of study one was to investigate whether the differences previously reported in the skeleton of competitive female gymnasts (high level gymnastics exposure) are also demonstrated in young children with a current or past participation history in recreational or precompetitive gymnastics (low level gymnastics exposure). One hundred and sixty three children (30 gymnasts, 61 ex-gymnasts, and 72 non-gymnasts) between 4 and 6 years of age were recruited and measured annually for four years. Total body (TB), lumbar spine (LS) and femoral neck (FN) bone mineral content (BMC) was measured by dual energy x-ray absorptiometry (DXA) at each measurement occasion. Bone mass, density, structure and estimated strength was determined using peripheral quantitative computed tomography (pQCT) at the radius and tibia during the third measurement occasion. Multilevel random effects models were constructed and used to predict differences in TB, LS and FN BMC between groups while controlling for differences in body size, physical activity and diet. Analysis of covariance (covariates of sex, age and height) was used to investigate differences in bone content, density, area, and estimated strength at the radius and tibia. Gymnasts had 3% more TB and 7% more FN BMC than children participating in other recreational sports at the fourth measurement occasion (p<0.05). Gymnasts were also found have 6-25% greater adjusted BMC, volumetric bone mineral density and estimated strength at the distal radius compared to non-gymnasts (p<0.05). These findings suggest that recreational and precompetitive gymnastics participation (low level gymnastics exposure) is associated with greater bone parameters. This is important as beginner gymnastics skills are attainable by most children and do not require a high level of training. Low-level gymnastics skills can easily be integrated into school physical education programs potentially impacting skeletal health.<p> Study 2: The purpose of study 2 was to assess whether the previously reported greater bone mineral content in premenarcheal gymnasts was maintained 10 years after the cessation of participation and removal of the gymnastics loading stimulus. In 1995, thirty elite premenarcheal female gymnasts were recruited into a study investigating the role of high impact physical activity on bone mass in childhood and compared to 30 non-gymnasts. In 2009-2010 gymnasts and non-gymnasts (n=60) were re-contacted and 25 retired gymnasts and 22 non-gymnasts consented to participate. Total body, LS, and FN BMC was assessed at both measurement occasions by DXA. Bone geometric and densitometric parameters were measured by pQCT at the radius and tibia in 2009/10. ANCOVA was used to compare gymnasts and non-gymnasts bone parameters while controlling for differences in age, body composition and maturation. Gymnasts had significantly greater size adjusted TB, LS, and FN BMC (15, 17, and 12%, respectively) at 12 years of age (1995) (p<0.05). At follow-up, retired gymnasts also had significantly greater size adjusted TB, LS, and FN BMC (13, 19 and 13%, respectively) (p<0.05). Furthermore, retired female gymnasts had greater bone area, content and estimated strength at the radius and greater BMC and estimated strength at the tibia compared to non-gymnasts (p<0.05). Premenarcheal gymnasts have bone benefits that were apparent in adulthood after long-term removal of the gymnastics loading stimulus. Low level gymnastics exposure was associated with greater bone parameters in childhood. If these benefits can be maintained, as is suggested in retired competitive gymnasts, recreational gymnastics participation has the potential to positively impact lifetime skeletal health.

Pain in sport serves the adaptive functions of signalling impending or actual injury and signalling the achievement of optimum workload to produce a conditioning effect. It is important to be able to distinguish what pain is signalling in order to respond to it effectively. The different functions of pain present a challenge for athletes wanting to improve their skill and conditioning level in the most efficient manner without becoming injured. However, this challenge could prove dangerous to children who have only a partial understanding of the value of pain, or who believe that they must endure great amounts of pain in order to become successful in sport. Previous research with general populations has demonstrated that children have a naive understanding of pain causation and do not understand the value of pain. In addition, previous research demonstrated that social factors such as peer and parental pressure may lead to situations where child athletes suffer preventable injuries because they ignore the warning signals of pain. Because coaches and parents are often responsible for deciding what to do when children present with pain, it is important for these adults to be aware of the cognitive limitations of children regarding the causes and meaning of pain. To date, there is no research which examines what athletes know about sport-related pain. Participants for this research project were 68 gymnasts aged 6 to 13 years. Several questions were asked in this study: (a) can gymnasts of various ages distinguish different types of sport-related pain?; (b) do gymnasts respond differently to different types of sport-related pain?; (c) what reasons do gymnasts give for continuing or discontinuing gymnastics when they have pain?; (d) do gymnasts understand the concept of pain causality?; (e) do gymnasts understand the value of pain?; (0 do gymnasts use pain for secondary gain? These questions were investigated in the context of an interview designed for this study. Two subtests from the Stanford-Binet Intelligence Scale and tests of cognitive developmental level based on Piagetian theory were also administered. The effects of age, gender, level of cognitive development, experience with sport, and experience with pain and injury were examined for their influence on responses to the above questions. Results revealed age differences in the gymnasts' ability to distinguish types of pain such that older gymnasts identified more pain types. However, even the youngest participants were able to discuss more than one type of pain. There were age differences in gymnasts' understanding of pain causality. Contrary to previous research demonstrating children to be unable to identify a physiological cause of pain, 32% of the gymnasts aged 9 to 13 were able to describe the role of the brain and/or nerves in pain causality. Also contrary to previous research with general populations, the gymnasts were able to discuss the value of pain, especially as a signal of hard work and as a warning to stop what they are doing. Forty percent of participants reported using pain (sport-related and/or non sport-related) for secondary gain. Not a single gymnast reported using pain as an excuse for a poor performance. Six of them did, however, report pretending to be in pain to avoid something in the gym that caused them fear. Further demonstrating an appreciation of different types of pain, results showed the gymnasts to respond differently to various pain types. These young athletes demonstrated an awareness of the need to stop their sport in some cases and to continue gymnastics in other cases, depending upon the type of pain. When continuing gymnastics despite pain, participants usually justified their decision by saying that the pain was not harmful to them. When describing why they discontinued gymnastics because of pain, participants often stated that the pain or injury may worsen. Few participants stated a concern for their future functioning. No participant described pressure from coaches, parents or peers to continue gymnastics while experiencing pain. Results are discussed in a variety of contexts: (a) comparison of these results to those of similar research done with general populations of children; (b) implications for training practices, coach and athlete education. and sport policy in general; (c) support for a theory of cognition that encompasses both nativist and constructivist components; and (d) directions for future research.

Osteoporosis, through its association with age-related fracture, is a major public health concern worldwide. Although osteoporosis was once considered a disease of the elderly, it is now recognized as a condition that has childhood antecedents. The capacity of bone to adapt is the greatest before puberty because of a higher rate of modeling and remodeling. Therefore, the amount of bone gained during childhood and adolescence has the potential to impact lifetime skeletal health. Children who participate in greater amounts of physical activity have greater bone mineral accrual in adolescence as well as a greater peak bone mass in young adulthood. Structured impact loading during growth also positively influences bone parameters. However, the intensity, duration and frequency of loading that is required to elicit skeletal benefits are not well established. Furthermore, although structured physical activity during growth has been hypothesized to delay or prevent the risk of osteoporosis and related fracture later in life there is no clear evidence of a persisting benefit once the loading stimulus has been removed. Therefore, the objective of this thesis was to investigate low-level impact loading during growth and skeletal development as well as to determine the influence of the withdrawal of the loading stimulus on adult bone parameters. Two studies were necessary to realize this objective. The findings should help to determine whether adolescent and adult bone health benefits from structured physical activity during growth. If this is found to be the case then structured gymnastic activity could be promoted as an effective means to optimize adult bone mass, structure and estimated strength.<p> Study 1: The purpose of study one was to investigate whether the differences previously reported in the skeleton of competitive female gymnasts (high level gymnastics exposure) are also demonstrated in young children with a current or past participation history in recreational or precompetitive gymnastics (low level gymnastics exposure). One hundred and sixty three children (30 gymnasts, 61 ex-gymnasts, and 72 non-gymnasts) between 4 and 6 years of age were recruited and measured annually for four years. Total body (TB), lumbar spine (LS) and femoral neck (FN) bone mineral content (BMC) was measured by dual energy x-ray absorptiometry (DXA) at each measurement occasion. Bone mass, density, structure and estimated strength was determined using peripheral quantitative computed tomography (pQCT) at the radius and tibia during the third measurement occasion. Multilevel random effects models were constructed and used to predict differences in TB, LS and FN BMC between groups while controlling for differences in body size, physical activity and diet. Analysis of covariance (covariates of sex, age and height) was used to investigate differences in bone content, density, area, and estimated strength at the radius and tibia. Gymnasts had 3% more TB and 7% more FN BMC than children participating in other recreational sports at the fourth measurement occasion (p<0.05). Gymnasts were also found have 6-25% greater adjusted BMC, volumetric bone mineral density and estimated strength at the distal radius compared to non-gymnasts (p<0.05). These findings suggest that recreational and precompetitive gymnastics participation (low level gymnastics exposure) is associated with greater bone parameters. This is important as beginner gymnastics skills are attainable by most children and do not require a high level of training. Low-level gymnastics skills can easily be integrated into school physical education programs potentially impacting skeletal health.<p> Study 2: The purpose of study 2 was to assess whether the previously reported greater bone mineral content in premenarcheal gymnasts was maintained 10 years after the cessation of participation and removal of the gymnastics loading stimulus. In 1995, thirty elite premenarcheal female gymnasts were recruited into a study investigating the role of high impact physical activity on bone mass in childhood and compared to 30 non-gymnasts. In 2009-2010 gymnasts and non-gymnasts (n=60) were re-contacted and 25 retired gymnasts and 22 non-gymnasts consented to participate. Total body, LS, and FN BMC was assessed at both measurement occasions by DXA. Bone geometric and densitometric parameters were measured by pQCT at the radius and tibia in 2009/10. ANCOVA was used to compare gymnasts and non-gymnasts bone parameters while controlling for differences in age, body composition and maturation. Gymnasts had significantly greater size adjusted TB, LS, and FN BMC (15, 17, and 12%, respectively) at 12 years of age (1995) (p<0.05). At follow-up, retired gymnasts also had significantly greater size adjusted TB, LS, and FN BMC (13, 19 and 13%, respectively) (p<0.05). Furthermore, retired female gymnasts had greater bone area, content and estimated strength at the radius and greater BMC and estimated strength at the tibia compared to non-gymnasts (p<0.05). Premenarcheal gymnasts have bone benefits that were apparent in adulthood after long-term removal of the gymnastics loading stimulus. Low level gymnastics exposure was associated with greater bone parameters in childhood. If these benefits can be maintained, as is suggested in retired competitive gymnasts, recreational gymnastics participation has the potential to positively impact lifetime skeletal health.

A computer simulation model of the table contact phase of gymnastics vaulting was developed to gain an understanding of the mechanics of this phase of the vault. The model incorporated a gymnast and a vaulting table, and used a novel two-state contact phase representation to simulate the interaction between these two bodies during the table contact phase. The gymnast was modelled in planar form using seven segments, with torque generators acting at the wrist, shoulder, hip and knee joints. The model also allowed for shoulder retraction and protraction, displacement of the glenohumeral joint centre and flexion/extension of the fingers. The table was modelled as a single rigid body that could rotate. The model was personalised to an elite gymnast so that simulation outputs could be compared with the gymnast's performance. Kinematic data of vaulting performances were obtained using a optoelectronic motion capture system. Maximal voluntary joint torques were also measured using an isovelocity dynamometer, and a torque - angle - angular velocity relationship was used to relate joint torques to joint angles and angular velocities. A set of model system parameters was determined using a gymnast-specific angle-driven model by matching four simulations to their respective performances concurrently. The resulting parameters were evaluated using two independent trials, and found to be applicable to handspring entry vaults. The torque-driven model was successfully evaluated, and shown to produce realistic movements, with mean overall differences between simulations and recorded performances of 2.5% and 8.6% for two different handspring entry vaults. The model was applied to further understanding of the mechanics of the table contact phase of gymnastics vaulting. Optimisation showed that there was limited potential (1.3%) for the gymnast to improve performance through technique changes during the table contact phase. However, with additional changes in configuration at table contact post-flight rotation could be increased by 9.8% and post-flight height could be increased by 0.14m. Angular momentum was found to always decrease during the table contact phase of the vault, although the reductions were less when maximising post-flight rotation.

Thesis (Ph. D.)--University of California, San Diego, 2000. / Vita. Includes bibliographical references (leaves 431-445).

Thesis (M.S.)--Western Washington University, 2005. / Includes bibliographical references (leaves 114-123). Also available online (PDF file) by a subscription to the set or by purchasing the individual file.

Thesis (M.S.)--Western Washington University, 2005. / Includes bibliographical references (leaves 114-123).

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