LAYING THE FOUNDATION TO BETTER BONE HEALTH IN OLDER AGE: EXERCISE
IN WEIGHT-BEARING, HIGH-IMPACT ACTIVITIES DURING GROWING YEARS
Gruodyte-Raciene R.1, Jurimae T.2, Jurimae J.2, Erlandson C. M.3, Baxter-Jones D.3, Adam G.3
1Lithuanian Sports University, Lithuania, 2University of Tartu, Estonia, 3University of Saskatchewan, Canada
Relevance of the research. Osteoporosis is traditionally considered to be a disease affecting the elderly. One of the most effective osteoporosis prevention strategies may be maximizing bone mineral content (BMC) during growing years by adopting weight-bearing physical activity (PA) in childhood and adolescence (French et al., 2000). Regular high-impact PA (such as ball games, racket sports, gymnastics, dance, running, or jumping exercises) during growth may play an important role in maximizing bone mineral mass gain, which may reduce the incidence of fractures in the elderly as well as in children and adolescents (Janz et al., 2010; Misra, 2008; Rizzoli et al., 2010).
Bone is a unique, metabolically active tissue that undergoes a continuous remodeling throughout its life cycle. The skeleton grows as the body grows, in length, breadth, mass, and volumetric density (Javaid, Cooper, 2002). There are two functionally distinct phases of bone development: 1) the skeletal patterning during the embryonic period; and 2) the mineralization, the location of which is influenced by mechanical strain (Davies et al., 2005). Bone mass increases substantially during the first two decades, reaching a plateau (i.e. peak bone mass) in the late teen or young adult years, remaining relatively stable throughout the early- to mid-adult years until the onset of the naturally progressive bone loss that accompanies ageing occurs (Faulkner, Bailey, 2007). Early puberty is a period of increased bone adaptation to mechanical loading due to the velocity of bone growth and endocrine changes at this time (Hind, Burrows, 2007).
The aim of the research is to investigate the effect of exercising gymnastics on bone parameters in children and adolescents.
Research methods and organization. Two studies were conducted to reveal the research aim:
1) a longitudinal (2006‒2012) study of Canadian children (4‒6 years of age at baseline; n = 165; males n = 81) involved in either recreational gymnastics (gymnasts) or other recreational sports (non-gymnasts) (Gruodyte-Raciene et al., 2013; Jackowski et al., 2015); and 2) a cross-sectional study of healthy adolescent (13–15-year-old) girls from different schools and sport clubs in Estonia (n = 202), comprising six groups, i.e. controls and those who for at least two recent years trained in sport games (basketball, volleyball, badminton), track sprint, rhythmic gymnastics, swimming, or cross-country skiing (Gruodyte, 2010). A dual-energy X-ray absorptiometry (DXA) method was used in both studies: to obtain the image of each child hip (study 1), and to measure the bone mineral density (BMD; g/cm2) and BMC (g) of the whole-body, femoral neck (FN) and lumbar spine (LS) of adolescent girls (study 2). Values of cross-sectional area (CSA), section modulus (Z), and cortical thickness (CT) at the narrow neck (NN), intertrochanter (IT), and shaft (S) of children’s hip were estimated using the hip structural analysis (HSA) program. In addition, peripheral quantitative computed tomography (pQCT) scans of their distal and shaft sites of the forearm and leg were obtained. Estradiol, insulin-like growth factor-1 (IGF-1), IGF-binding protein-3 (IGFBP-3), visfatin, adiponectin, leptin, insulin and glucose were measured in pubertal girls (study 2). Multilevel random effects models were constructed and used to develop bone structural strength development trajectories (estimate ± SEE) (study 1).
Results and discussion. Once the confounders of body size and lifestyle of children (study 1) were controlled, it was found that gymnasts had 6 % greater NN CSA than nongymnast controls (0.09 ± 0.03 cm2, p < 0.05), 7 % greater NN Z (0.04 ± 0.01 cm3, p < 0.05), 5 % greater IT CSA (0.11 ± 0.04 cm3, p < 0.05), 6 % greater IT Z (0.07 ± 0.03 cm3, p < 0.05), and 3 % greater S CSA (0.06 ± 0.03 cm3, p < 0.05). Also, individuals exposed to recreational gymnastics had significantly greater total bone area (ToA; 18.0 ± 7.5 mm2) and total bone content (ToC; 6.0 ± 3.0 mg/mm) at the distal radius (p < 0.05). This represents an 8–21 % benefit in ToA and 8–15 % benefit to ToC from 4 to 12 years of age. Exposure to recreational gymnastics had no significant effect on bone measures at the radius shaft or at the tibia (p > 0.05).
After adjusting for age, body height, and body mass, the significant correlations were found between BMD values (at both FN & LS) and the levels of estradiol, IGF-1, and IGF-1/IGFBP-3 molar ratio (r = 0.46–0.60) only in rhythmic gymnasts’ group. Similarly, only in this group the adjusted significant correlations of FN BMC with IGF-1 and IGF-1/IGFBP-3 molar ratio were found. Stepwise multiple regression analysis indicated that IGF-1 and estradiol together explained 42.6 % (R2 x 100) of the total variance at the FN BMD, and IGF-1 alone 35.4 % (R2 x 100) of the total variance at FN BMC in rhythmic gymnasts group only. Leptin concentrations correlated positively with FN & LS BMD and FN BMC in the rhythmic gymnasts’ group only, even after adjustment for age, body height, and body mass (r = 0.41–0.63).
Conclusions. These results suggest that early exposure to low level gymnastics participation confers benefits related to geometric and bone architecture properties during childhood, and if maintained may improve bone health in adolescence and adulthood. Continuous high-impact PA, especially rhythmic gymnastics, has beneficial effects on the development of various bone parameters as it was revealed in our cross-sectional study of pubertal girls with different training patterns.
