Exercise-induced training effects on bone mineral content: a 7-year follow-up study with adolescent female gymnasts and runners

Skeletal Loading: Lean and Bone Mass Development in Young Elite Male Gymnasts, Swimmers, and Nonathletes Aged 6-24 Years

BACKGROUND

Exercise optimizes peak bone mass accrual, particularly if the loading is high magnitude and distributed in abnormal directions. Little is known about the influence of early intense training in sport during peak bone mass accrual, especially in boys.

METHODS

Ninety-eight males aged 6-24 years (gymnasts, swimmers, and controls) completed the bone-specific physical activity questionnaire and a 7-day exercise diary. Dual-energy X-ray absorptiometry determined bone mineral properties of the total body (less head) and lumbar spine (LS, L1-L4) and total lean mass. Subgroup analyses were conducted for juniors (prepubescent), adolescents (11-16 y), and seniors (17-24 y).

RESULTS

Lean mass was positively associated with total body less head and LS bone outcomes in all 3 age groups (R2 = .632-.770, P < .05), and bone-specific physical activity questionnaire scores were associated with LS bone mineral density in adolescents and seniors (R2 = .440 and .591, P < .05). Senior gymnasts had significantly higher LS bone mineral density (in grams per square centimeter) and Z-scores than swimmers (P = .004) and controls (P = .012).

CONCLUSIONS

Elite gymnastics is associated with superior peak bone mass accrual in young males. The benefits appear more pronounced during young adulthood compared with prepuberty, potentially reflecting an extended time course for bone adaptation.

Calcium and phosphorus supplemented diet increases bone volume after thirty days of high speed treadmill exercise in adult mice

Weight-bearing exercise increases bone mass and strength. Increasing bone loading frequency during exercise can strengthen bone. Combining exercise with a calcium- and phosphorus-supplemented diet increases cortical area more than exercise alone in mice. Thus, we hypothesized that combining high-speed treadmill exercise while feeding mice a mineral-supplemented diet would lead to greater cortical area than high-speed exercise on a standard diet and low-speed exercise on a supplemented diet. Fifteen-week old male C57BL/6 mice were assigned to seven groups—(1) baseline, (2) non-exercise fed a control diet, (3) non-exercise fed a supplemented diet, (4) low-speed exercise fed a control diet, (5) low-speed exercise fed a supplemented diet, (6) high-speed exercise fed a control diet, and (7) high-speed exercise fed a supplemented diet. Mice exercised thirty days for 20 min/day at 12 m/min or 20 m/min. Tibiae were assessed by micro-CT and 4-point bending. Cortical area fraction and trabecular bone volume fraction (BV/TV) were significantly increased by the supplemented diet. High-speed exercised mice had significantly lower body weight, with no detrimental effects to bone health. Increasing running speed can decrease body weight while maintaining the benefits of exercise and nutrition on bone health. Running can lower body weight without harming bone health.

Combined mineral-supplemented diet and exercise increases bone mass and strength after eight weeks and maintains increases after eight weeks detraining in adult mice

Exercise has long-lasting benefits to bone mass and structural strength even after cessation. Combining exercise with a calcium- and phosphorus-supplemented diet increases cortical bone mineral content (BMC), area, and yield force more than exercise alone in adult mice. These increases could also be maintained after stopping exercise if the modified diet is maintained. It was hypothesized that combining exercise with a mineral-supplemented diet would lead to greater cortical BMC, area, and yield force immediately after a lengthy exercise program and after an equally long period of non-exercise (detraining) in adult mice. Male, 16-week old C57Bl/6 mice were assigned to 9 weight-matched groups–a baseline group, exercise and non-exercise groups fed a control or mineral-supplemented diet for 8 weeks, exercise + detraining and non-exercise groups fed a control or mineral-supplemented diet for 16 weeks. Exercise + detraining consisted of 8 weeks of exercise followed by 8 weeks without exercise. The daily exercise program consisted of running on a treadmill at 12 m/min, 30 min/day. After 8 weeks, mice fed the supplemented diet had greater tibial cortical BMC and area, trabecular bone volume/tissue volume (BV/TV), bone mineral density (vBMD), yield force, and ultimate force than mice fed the control diet. Exercise increased cortical BMC and area only when coupled with the supplemented diet. After 16 weeks, both exercised and non-exercised mice fed the supplemented diet maintained greater tibial cortical BMC and area, trabecular BV/TV, vBMD, yield force, and ultimate force than mice fed the control diet. Combining exercise with a mineral-supplemented diet leads to greater bone mass and structural strength than exercise alone. These benefits remain after an equally long period of detraining. Long-term use of dietary mineral supplements may help increase and maintain bone mass with aging in adult mice.

Exercise characteristics influence femoral cross-sectional geometry: a magnetic resonance imaging study in elite female athletes

The associations between mid-femoral cross-sectional geometry and exercise characteristics were investigated in female athletes. The effects on bone geometry for weight-bearing sports with low-to-high-impact were greater than those for non-impact weight-bearing sports, whereas low-impact or high-strain-magnitude/low-strain-rate sports had less of an effect on bone geometry compared with higher-impact sports.

INTRODUCTION

Many previous studies have investigated tibial geometry in athletes; however, few studies have examined the associations between femoral cross-sectional geometry and exercise characteristics. The aim of this study was to investigate these relationships using magnetic resonance imaging (MRI) at the femoral mid-shaft.

METHODS

One hundred and fifty-three female elite athletes, aged 18-34 years, were classified into five groups based on the characteristics of their sports. Sports were considered non-impact (n = 27), low- or moderate-impact (n = 39), odd-impact (n = 38), high-strain-magnitude/low-strain-rate (n = 10), or high-impact (n = 39). Bone geometrical parameters, including cortical area, periosteal perimeter, and moment of inertia (bone strength index), were determined using MRI images.

RESULTS

Higher-impact groups displayed bone expansion, with significantly greater periosteal perimeters, cortical areas (~37.3%), and minimum moments of inertia (I(min,) ~92.3%) at the mid-femur than non- and low-impact groups. After adjusting for age, height, and weight, the cortical area and I(min) of the low-impact and high-strain-magnitude/low-strain-rate groups were also significantly greater than those of the non-impact group.

CONCLUSIONS

Higher-impact sports with high strain rates stimulated periosteal bone formation and improved bone geometry and strength indices at the femoral mid-shaft. Although our results indicate that weight-bearing sports are beneficial even if they are low impact, the effects of lower-impact or high-strain-magnitude/low-strain-rate sports on bone geometry were less pronounced than the effects of higher-impact sports at the femoral mid-shaft.

Skeletal adaptations associated with pre-pubertal gymnastics participation as determined by DXA and pQCT: a systematic review and meta-analysis

Participation in gymnastics prior to puberty offers an intriguing and unique model, particularly in girls. The individuality comes from both upper and lower limbs being exposed to high mechanical loading through year long intensive training programs, initiated at a young age. Studying this unique model and the associated changes in musculoskeletal health during growth is an area of specific interest. Previous reviews on gymnastics participation and bone health have been broad; and not limited to a particular maturation period, such as pre-puberty.

OBJECTIVES

To determine the difference in skeletal health between pre-pubertal girls participating in gymnastics compared with non-gymnasts.

DESIGN

Meta-analysis.

METHODS

Following a systematic search, 17 studies were included in this meta-analysis. All studies used dual-energy X-ray absorptiometry to assess bone mineral density and bone mineral content. In addition, two studies included peripheral quantitative computed tomography.

RESULTS

Following the implementation of a random effects model, gymnasts were found to have greater bone properties than non-gymnasts. The largest difference in bone health between gymnasts and non-gymnasts was observed in peripheral quantitative computed tomography-derived volumetric bone mineral density at the distal radius (d=1.06).

CONCLUSIONS

Participation in gymnastics during pre-pubertal growth was associated with skeletal health benefits, particularly to the upper body.