Effect of physical training on bone mineral density in prepubertal girls: A comparative study between impact-loading and non-impact-loading sports

Abstract

Physical activity is known to have an anabolic effect on bone tissue. It has been shown to increase the bone mineral density (BMD) in young adults, as well as in teenagers. But there is little information about the effect of intensive physical activity in childhood, particularly at the prepubertal stage. To examine the influence of an early intensive physical training on BMD, we have studied a group of elite prepubertal girls, at the starting phase of their peak bone mass acquisition. Subjects were engaged either in sport requiring significant impact loading on the skeleton, or in sport without impact loading. Forty-one healthy prepubertal girls took part in this study. The sport group consisted of 10 swimmers (10.5 +/- 1.4 years old) and 18 gymnasts (10.4 +/- 1.3 years old), who had performed 3 years of high-level sport training (8-12 h per week for swimmers, 10-15 h per week for gymnasts). Thirteen girls (10.7 +/- 1 years old) doing less than 3 h per week of physical activity served as a control group. BMD measurements were done using dual-energy X-ray absorptiometry. There was no statistical significant difference between groups as regards age, body height and weight, and body composition. There was no statistical significant difference between swimmers and controls for all the BMD measurements. Mean BMD in gymnasts was statistically higher than in the control group for mid-radius (+15.5%, p < 0.001), distal radius (+33%, p < 0.001), L2-4 vertebrae (+11%, p < 0.05), femoral neck (+15%, p < 0.001) and Ward's triangle (+15%, p < 0.01). Moreover, in gymnasts, BMD at radius, trochanter and femoral neck was above normative values. We conclude that physical activity in childhood could be an important factor in bone mineral acquisition in prepubertal girls, but only if the sport can induce bone strains during a long-term program: gymnastics has such characteristics, unlike swimming. Such acquisition could provide protection against risks of osteoporosis in later life, but this remains debatable.

Daily Physical Education in the School Curriculum in Prepubertal Girls during 1 Year is Followed by an Increase in Bone Mineral Accrual and Bone Width—Data from the Prospective Controlled Malmö Pediatric Osteoporosis Prevention Study

“…The so far published prospective controlled exercise intervention studies, most elegant support this view (14)(15)(16)(18)(19)(20), whereas similar effects could not be found in the post-pubertal period (12). Furthermore, published data indicate that the physical activity ought to include high-impact activities (21)(22)(23)(24) and that the training should probably be initiated before or in early puberty (25), if the purpose is to reach the most beneficial anabolic skeletal effects. There is also evidence that moderate intense school-based physical education classes do increase the level of physical activity and improve the physical fitness (26).…”

The Effects of Trabecular-Bone Loading Variables on the Surface Signaling Potential for Bone Remodeling and Adaptation

“…In growth or adaptation they change the shape of trabecular morphology and adapt it to external loading direction and magnitude 7,41,43 in a process called 'modeling'. 12 In adulthood the tissue is continuously renewed by the same cells in a process called 'remodeling'.…”

Level of serum undercarboxylated osteocalcin correlates with bone quality assessed by calcaneal quantitative ultrasound sonometry in young Japanese females

“…All subjects were physically active college students, as the majority of them belonged to a college sports club, though they were not initially selected based on physical activity. This may account for the improved bone quality of this group, since physical activity positively correlates with bone status (27,28).…”

“…Ohta et al (30) reported that the 25-OH-D level in 274 Japanese women aged 19-25 years was 18.7±4.8 ng/ml. As with bone quality, the physical activity of the subjects may contribute to the vitamin D status (27,28), though it is unknown whether subjects in the Ohta et al study were more physically active.…”