High-Impact Exercise and Bones of Growing Girls: A 9-Month Controlled Trial

Abstract

The maximum amount of bone a person can obtain during the first two decades of life is an important determinant of bone mass in later life, and an increase in peak bone mass has been associated with decreased risk for osteoporotic fractures. It is known that growth of bone and thus development of peak bone mass are strongly controlled by genetic factors, but information on the role of environmental factors, such as exercise and nutrition, (e.g., exercise) on growing bone is limited. We tested a hypothesis that in growing girls the benefit of mechanical loading on bone mineral mass and bone strength is better before rather than after the menarche. Sixty-four girls (25 premenarcheal, 39 postmenarcheal) carried out a supervised 9-month step-aerobic program (two sessions per week), each session complemented with additional jumps. Sixty-two girls (33 premenarcheal, 29 postmenarcheal) served as controls. Bone mineral content (BMC) at the lumbar spine and proximal femur was measured by dual-energy X-ray absorptiometry (DXA). In addition, the cortical density (CoD, mg/cm3) and cortical cross-sectional area (CoA, mm2) and the density-weighted polar section modulus (BSI, mm3) of the tibial midshaft were determined by peripheral quantitative tomography (pQCT). In the premenarcheal girls, BMC increased statistically significantly more in the trainees than controls at the lumbar spine (p = 0.012) (8.6% vs 5.3%) and femoral neck (p = 0.014) (9.3% vs 5.3%). In the tibial midshaft, the intergroup differences (CoD, CoA and BSI) were not significant. The postmenarcheal girls showed no significant post-training intergroup differences in any of the bone parameters (BMC increased in the lumbar spine 6.0% vs 4.9%; femoral neck 3.4% vs 3.2%; and trochanter 2.6% vs 3.5%). Although a large proportion of bone mineral increase in the growing girls of this study was attributable to growth itself, this 9-month exercise intervention showed that a clear and large additional bone gain could be obtained in exercising premenarcheal girls, but not in exercising postmenarcheal girls. In other words, exercise seemed more beneficial for additional bone mineral acquisition before menarche (i.e., during the growth spurt) rather than after it.

Higher premenarcheal bone mass in elite gymnasts is maintained into young adulthood after long-term retirement from sport: A 14-year follow-up

“…This finding suggests a potential for the gymnastics loading stimulus to be overriding the natural tendency for later-maturing individuals to have less bone mass in young adulthood. However, it should also be noted that other studies suggest bone may be most responsive to mechanical loading before puberty, (42,43) which was when the current cohort was actively training.…”

Effects of a Specialist-Led, School Physical Education Program on Bone Mass, Structure, and Strength in Primary School Children: A 4-Year Cluster Randomized Controlled Trial

“…(3) However, of the four school-based exercise interventions that used pQCT to assess bone geometry, all failed to observe any significant exercise-induced benefits on measures of tibial bone structure, (6,(26)(27)(28) which may relate to the relatively short duration of these trials (9 to 16 months). In contrast, we observed that our 4-year generalized PE program focusing on core movements, coordination and agility, skill activities, movement challenges and games, and dynamic movement control improved midshaft cortical area and/or thickness in young girls and boys, but this did not translate into greater gains in bone strength.…”

Does Exercise Influence Pediatric Bone? A Systematic Review

“…Heinonen et al [23] reported greater gains in femoral neck and spine bone mineral content in females in early puberty who participated in the exercise intervention than those who did not, but no difference was observed in females who were postpubertal. A school-based study by Meyer et al [41] included two different age groups (6-7 and 11-12 year olds) to specifically determine whether the bone response to exercise Fig.…”

“…Of these trials, 14 were excluded because of duplication of study populations (Table 1), and one did not present measures of variance for changes in bone outcomes [8]. Two studies had inconsistencies between tables or between tables and graphs resulting in only a fraction of the bone data being used [23,42]. Authors of two studies provided mean percent changes and SDs of percent change by sex and pubertal status for control and intervention groups because these could not be determined from the articles [41,54].…”

“…Results from each of these subgroups were used in this review. In addition, three studies were designed specifically to investigate the effect of exercise on bone by pubertal status [23,35,41]. To compare study findings, mean percent changes in bone outcomes were determined for each subgroup and results were expressed as percent change from baseline.…”