Competitive effect between fat free mass and adipous tissue on bone mineral density gains of lower members of sports adolescents: abcd-growth study

Author(s)

Rafael Luiz de Marco

• Document type: Master's Dissertation
• Press: Presidente Prudente. 2019-04-22.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências e Tecnologia. Presidente Prudente
• Defense date: 2019-03-28
• Advisor: Romulo Araújo Fernandes

Abstract

Bone health has received increasing attention from the academic community and society because of the great social and economic weight that osteoporosis represents. On the other hand, the development of osteoporosis in old age is strongly determined by events that occur in youth, in this case the low gains of bone mass. In this sense, the action of the muscular tissue in the strengthening of the bone structure has been investigated in young people, but many gaps still exist. Objective: To discriminate the impact of changes in lean soft tissue (LST) and body fat (BF) on the bone gain of adolescents of both sexes, as well as to identify the effect of both tissues on the bone gains in conditions involving different levels of impact mechanic, in environment of hypogra-phy (swimming), environment without sports (control group) and environment with sports practice with impact (soccer, basketball and martial arts). Methods: A longitudinal study with twelve months of follow-up (two moments of data collection) that was conducted in the city of Presidente Prudente - SP. The sample consisted of 262 young people classified as: Control, Swimming and Impact Sports (combined forms: karate, judo, kung-fu, soccer, basketball and volleyball). Bone mineral density (BMD), LST and BF were estimated by means of the dual energy X-ray absorptiometry in the i) lower limbs, ii) the left leg and iii) the right leg. Confounding variables were: chronological age, biological maturation, and vitamin D intake. Results: First, according to the analyzes presented, it can be observed that LST is the most relevant determinant of BMD gain explaining the variance found in BMD of lower limbs in 56% (adjusted R2 = 0.569) when considering the effects of gender, age and somatic maturation, on the other hand, BF does not seem to significantly affect BMD. In longitudinal analyzes (after twelve months of follow-up and adjusted for confounding factors), it can be observed that for the whole sample group and for those who practice sport of impact, LST was the most determinant variable for the accumulation of BMD in the lower limbs with mean for both legs approximately above 55% explanation. When the sample was divided by sex, it can be observed that for boys, LST was the greatest predictor for BMD accumulation in lower limbs, but for females BF was the variable that had the most explanation for BMD accumulation in lower limbs (both legs). Conclusions: The findings of the present study conclude that LST is the most relevant determinant regarding BMD gain in lower limbs in adolescent males even when considering the effects of sex, age and somatic maturation. On the other hand, longitudinally, lower limb BF seems to significantly affect BMD accumulation of lower limbs of female adolescents over 12 months. (AU)

• FAPESP's process: 17/13003-9 - Concurrent effect of lean soft tissue and adipose tissue on bone density gains of lower limbs among adolescent engaged in sports: ABCD-growth study
• Grantee: Rafael Luiz de Marco
• Support Opportunities: Scholarships in Brazil - Master