High-impact exercise promotes bone gain in well-trained female athletes

Does Swimming Exercise Impair Bone Health? A Systematic Review and Meta-Analysis Comparing the Evidence in Humans and Rodent Models

BACKGROUND

The effect of swimming on bone health remains unclear, namely due to discrepant findings between studies in humans and animal models.

OBJECTIVE

The aim of this systematic review and meta-analysis is to identify the available evidence on the effects of swimming on bone mass, geometry and microarchitecture at the lumbar spine, femur and tibia in both humans and rodent animal models.

METHODS

The study followed PRISMA guidelines and was registered at PROSPERO (CRD4202236347 and CRD42022363714 for human and animal studies). Two different systematic literature searches were conducted in PubMed, Scopus and Web of Science, retrieving 36 and 16 reports for humans and animal models, respectively.

RESULTS

In humans, areal bone mineral density (aBMD) was similar between swimmers and non-athletic controls at the lumbar spine, hip and femoral neck. Swimmers' tibia diaphysis showed a higher cross-sectional area but lower cortical thickness. Inconsistent findings at the femoral neck cortical thickness were found. Due to the small number of studies, trabecular microarchitecture in human swimmers was not assessed. In rodent models, aBMD was found to be lower at the tibia, but similar at the femur. Inconsistent findings in femur diaphysis cross-sectional area were observed. No differences in femur and tibia trabecular microarchitecture were found.

CONCLUSION

Swimming seems to affect bone health differently according to anatomical region. Studies in both humans and rodent models suggest that tibia cortical bone is negatively affected by swimming. There was no evidence of a negative effect of swimming on other bone regions, both in humans and animal models.

The effect of regular running on the bone tissue of middle-aged men and women

BACKGROUND

Many authors consider running to be a protective physical activity (PA) in bone health. However, many studies also show inconsistencies in their results. The objective of the study is to analyze the effect of cumulative loading rate (TCL) on the bone mass of middle-aged runners and non-runners is assessed.

METHODS

This cross-sectional study included 322 individuals. There were 212 runners (109 male, 103 female) and those were individuals who did >10 km of running per week. There were 110 non-runners (54 male, 56 female). This group included individuals who did not adhere to the WHO (2020) recommendations for PA. The average age in the individual groups ranged from 40.9±4.1 to 42.3±4.8 years. Bone parameters were measured on the lower extremities and vertebral spine using the DXA method (Hologic QDR Horizon A). Multi-regression dependencies analysis was used to assess the results.

RESULTS

The results of the multi-regression dependencies analysis showed that the bone mineral content (BMC) and bone mineral density (BMD) are significantly influenced by the TCL and gender.

CONCLUSIONS

Therefore, we can conclude that running could be a suitable PA for preventing the reduction of BMD in the middle-aged population, especially in the lower limbs.

High prevalence of low bone mineral density but normal trabecular bone score in Norwegian elite Para athletes

Background

Low bone mineral density (BMD) increases the risk of bone stress injuries (BSI) and is one of several clinical concerns in Para athlete sports medicine. However, whether bone microarchitecture is altered in Para athletes is not known.

Objective

We aimed to investigate BMD, bone microarchitecture and incidence of bone stress injuries in Norwegian elite Para athletes.

Design

In this cross-sectional study in Para athletes, Dual energy x-ray absorptiometry (iDXA, Lunar, GE Health Care) derived areal BMD, trabecular bone score (TBS), a surrogate marker for bone microarchitecture, and body composition (body weight (BW), lean body mass (LBM), fat mass (FM), fat percentage) were investigated and compared between ambulant and non-ambulant athletes. Also, the association between BMD, TBS and body composition variables was investigated. Incidence of BSI was assessed with a questionnaire and confirmed by a sports physician in a clinical interview. BMD Z-score <-1 was defined as low and ≤-2 as osteoporotic. TBS ≥ 1.31 was normal, 1.23-1.31 intermediate and <1.23 low.

Results

Among 38 athletes (26 ± 6 yrs, 14 females), BMD Z-score was low in 19 athletes, and osteoporotic in 11 athletes' lumbar spine (LS) or femoral neck (FN). BMD was lower in non-ambulant vs. ambulant athletes both in LS (1.13 ± 0.19 vs. 1.25 ± 0.14 g/cm2, p = 0.030) and FN (0.90 ± 0.15 vs. 1.07 ± 0.16 g/cm2, p = 0.003). TBS was normal for all athletes. BMD Z-score in LS was positively associated with TBS (r = 0.408, p = 0.013), body weight (r = 0.326, p = 0.046) and lean body mass (r = 0.414, p = 0.010), but not with fat mass or fat percentage. None of the athletes reported any BSI.

Conclusions

Half of the Norwegian elite Para athletes had low BMD, and 29% had BMD Z-score <-2 suggesting osteoporosis. Non-ambulant athletes were more prone to low BMD than ambulant athletes. However, despite high prevalence of low BMD, TBS was normal in all athletes, and BSI was absent in this young population.

Bone bending strength and BMD of female athletes in volleyball, soccer, and long-distance running

PURPOSE

The purpose of the study was to determine whether sports training comprised of (1) high-impact loading sport in volleyball (VOL), (2) odd impact loading sport in soccer (SOC), and (3) low impact sport in distance running (RUN) were associated with tibial bending strength and calcaneus bone mineral density (BMD), and ulnar bending strength and wrist BMD.

METHOD

Female athletes comprised of 13 VOL, 22 SOC, and 22 RUN participated in the study. Twenty-three female non-athletes (NA) served as the comparison group. Tibial and ulnar bending strength (EI, Nm2) were assessed using a mechanical response tissue analyzer (MRTA). Calcaneus and wrist BMD were assessed using a peripheral X-ray absorptiometry. Group means differences among the study groups were determined using ANCOVA with age, weight, height, percent body fat, ethnicity/race, and training history serving as covariates.

RESULTS

Tibial EI of VOL (228.3 ± 138 Nm2) and SOC (208.6 ± 115 Nm2) were greater (p < 0.05) compared to NA (101.2 ± 42 Nm2). Ulnar EI of SOC (54.9 ± 51 Nm2) was higher (p < 0.05) than NA (27.2 ± 9 Nm2). Calcaneus BMD of VOL (0.618 ± 0.12 g/cm2), SOC (0.621 ± 0.009 g/cm2), and RUN (0.572 ± 0.007 g/cm2) were higher (p < 0.05) than NA (0.501 ± 0.08 g/cm2), but not different between athletic groups. Wrist BMD of VOL (0.484 ± .06 g/cm2) and SOC (0.480 ± 0.06 g/cm2) were higher (p < 0.05) than NA (0.443 ± 0.04 g/cm2).

CONCLUSIONS

Female VOL athletes exhibit greater tibial bending strength than RUN and NA, but not greater than SOC. Female SOC athletes exhibit greater ulnar bending strength and wrist BMD than NA.

Lower bone mineral density can be a risk for an enlarging bone marrow lesion: A longitudinal cohort study of Japanese women without radiographic knee osteoarthritis

OBJECTIVES

The aim is to elucidate the relationship between bone mineral density (BMD) at baseline and the change of bone marrow lesion (BML) during a 2-year follow-up (2YFU) period.

METHODS

Seventy-eight female participants (mean age: 54.9 ± 9.6 years) without radiographic knee osteoarthritis were eligible. Based on right-knee magnetic resonance imaging, maximum BML area (BMLa) was calculated by tracing the BML border. The change in BMLa was defined using the following formula: [2YFU] - [Baseline] = ΔBMLa. Positive ΔBMLa was defined as enlarged; negative ΔBMLa was defined as regressed. Dual-energy X-ray absorptiometry was performed to measure the BMD of distal radius. Young adult mean [YAM (%)] of the BMD was used for statistical analysis. Linear regression analysis was conducted with ΔBMLa as the dependent variable and YAM as the independent variable. Receiver operating characteristic curve and logistic regression analyses were conducted for YAM to predict the prevalence of BML enlargement or regression.

RESULTS

Twenty-six (33.3%) patients had enlarged BMLa, 12 (15.4%) participants showed regressing BMLa, and 40 (51.3%) patients remained stable. YAM was negatively associated with ΔBMLa (β: - 0.375, P = 0.046). The best predictor of BML enlargement risk was 85% (odds ratio: 8.383, P = 0.025).

CONCLUSIONS

Lower BMD could predict BML enlargement during a 2YFU period.

A 2-Year Longitudinal Study of Bone Mineral Density in Collegiate Distance Runners

ABSTRACT

Brimacomb, OE, Martinez, MP, McCormack, WP, and Almstedt, HC. A 2-year longitudinal study of bone mineral density in collegiate distance runners. J Strength Cond Res XX(X): 000-000, 2022-The purpose of this investigation was to examine changes in bone mineral density (BMD) of male and female collegiate distance runners over 2 years. Bone mineral density of 29 collegiate distance runners (16 men and 13 women) were measured 5 times over 24 months using dual-energy x-ray absorptiometry (DXA) at the anterior-posterior (AP) and lateral (LAT) spine, femoral neck (FN), total hip (TH), whole body (WB), and ultradistal (UD) forearm. Repeated-measures multivariate analysis of covariance, with bone-free lean mass (BFLM) as covariate, was used to compare mean BMD values. Adjusted for BFLM, there were no significant differences (p > 0.05) in BMD at any site between sexes. There were no significant differences at the AP or LAT spine, FN, or WB between visit 1 and 5 for either sex. There was a significant increase in BMD (p = 0.044) at the UD forearm over 2 years in males. However, 56% of the men (n = 9) had a Z-score < -1.0 at the UD forearm. Seven of 11 women had Z-scores < -1.0 at the LAT spine and 4 of 13 had Z-scores < -1.0 at the AP spine. There were no significant changes in BMD at any site over the 2-year time frame, except a significant increase in BMD at the nondominant forearm in men. The spine appears to be an area of concern for women in this study when examining Z-score results. Coaches and medical staff need to continually educate collegiate endurance athletes about the importance of achieving and maintaining BMD through their college years.

The 100 Most-Cited and Influential Articles in Collegiate Athletics

Background

Bibliometric citation analyses have been widely used in medicine to help researchers gain foundational knowledge about a topic and identify subtopics of popular interest for further investigations. There is a lack of similar research in collegiate athletics.

Purpose

To identify the 100 most-cited research publications related to collegiate athletics.

Study Design

Cross-sectional study.

Methods

The Clarivate Analytics Web of Knowledge database was used to generate a list of articles relating to collegiate athletics on January 24, 2022. Articles were filtered by the total number of citations, and the 100 most-cited articles were selected. For each article, we identified and analyzed the following: author name, publication year, country of origin, journal name, article type, main research topic area, competitive level, sex of study population, and level of evidence.

Results

Of the top 100 most-cited articles, 63 were related to medicine. In total, 96% of articles were published in the United States, and 80% were published in the year 2000 or later. Of the top 100 articles, 85 were observational; only 5 were experimental. The sport most represented was soccer, followed by football, baseball, and basketball. Of the top 100 articles, 21 were published in a single journal, the American Journal of Sports Medicine. Ten authors published ≥5 of the top 100 most-cited studies.

Conclusion

The majority of top 100 articles were published in the United States after 1999 and primarily focused on medicine-related topics. Soccer was studied by more articles than football, baseball, and basketball. An author's prestige may have influenced the likelihood of citation. The top 100 most-cited studies provide researchers, medical students, residents, and fellows with a foundational list of the most important and influential academic contributions to the literature on collegiate athletics.

Comparison of Tibial Geometry, Density, and Strength in College-Aged Female Eumenorrheic Dancers, Gymnasts, and Runners: A Peripheral Quantitative Computed Tomography Study

INTRODUCTION

Weightbearing activities such as gymnastics, soccer, weightlifting, and running have often been used as benchmarks in skeletal research since they have been shown to promote densitometric and geometric benefits. In comparison with other sports, there is a paucity of information in relation to dance and its osteogenic potential.

OBJECTIVE

This study aimed to compare tibial geometry, density, and strength in college-aged dancers versus gymnasts and runners.

METHODS

A total of 60 trained eumenorrheic collegiate-aged female dancers (n = 11), gymnasts (n = 11), runners (n = 19), and sedentary controls (n = 19) were included in the study. Bone measurements, including total area (ToA), volumetric (total vBMD) and cortical density (CoD), compressive bone strength (BSI), and polar strength stress index (SSIp) of the dominant limb, were assessed using peripheral quantitative computed tomography (pQCT) at the distal and proximal tibia (4% and 66% of limb length).

RESULTS

No significant differences in ToA, CoD, CoA, and total vBMD were found between dancers and the comparison athletes at the measured sites. In addition, strength indices (BSI and SSIp) at the distal and proximal sites were similar between the dancing and both athlete groups.

CONCLUSION

Results suggest dance elicits similar structural adaptations at the tibia compared to benchmark high-impact and repetitive impact sports; thus, indicating dance, in its various forms, can have a positive effect on important bone variables that influence density and strength. These adaptations may potentially delay or prevent bone fragility later in life. Future studies should compare individual styles of dance separately, longitudinally, and include other important lower (e.g., hip) and upper body (e.g., radius) sites to further identify which forms provide the greatest osteogenic benefits.

Strength Training in Swimming

This narrative review deals with the topic of strength training in swimming, which has been a controversial issue for decades. It is not only about the importance for the performance at start, turn and swim speed, but also about the question of how to design a strength training program. Different approaches are discussed in the literature, with two aspects in the foreground. On the one hand is the discussion about the optimal intensity in strength training and, on the other hand, is the question of how specific strength training should be designed. In addition to a summary of the current state of research regarding the importance of strength training for swimming, the article shows which physiological adaptations should be achieved in order to be able to increase performance in the long term. Furthermore, an attempt is made to explain why some training contents seem to be rather unsuitable when it comes to increasing strength as a basis for higher performance in the start, turn and clean swimming. Practical training consequences are then derived from this. Regardless of the athlete's performance development, preventive aspects should also be considered in the discussion. The article provides a critical overview of the abovementioned key issues. The most important points when designing a strength training program for swimming are a sufficiently high-load intensity to increase maximum strength, which in turn is the basis for power, year-round strength training, parallel to swim training and working on the transfer of acquired strength skills in swim training, and not through supposedly specific strength training exercises on land or in the water.

Impact of Treadmill Interval Running on the Appearance of Zinc Finger Protein FHL2 in Bone Marrow Cells in a Rat Model: A Pilot Study

Although the benefits of physical exercise to preserve bone quality are now widely recognized, the intimate mechanisms leading to the underlying cell responses still require further investigations. Interval training running, for instance, appears as a generator of impacts on the skeleton, and particularly on the progenitor cells located in the bone marrow. Therefore, if this kind of stimulus initiates bone cell proliferation and differentiation, the activation of a devoted signaling pathway by mechano-transduction seems likely. This study aimed at investigating the effects of an interval running program on the appearance of the zinc finger protein FHL2 in bone cells and their anatomical location. Twelve 5-week-old male Wistar rats were randomly allocated to one of the following groups (n = 6 per group): sedentary control (SED) or high-intensity interval running (EX, 8 consecutive weeks). FHL2 identification in bone cells was performed by immuno-histochemistry on serial sections of radii. We hypothesized that impacts generated by running could activate, in vivo, a specific signaling pathway, through an integrin-mediated mechano-transductive process, leading to the synthesis of FHL2 in bone marrow cells. Our data demonstrated the systematic appearance of FHL2 (% labeled cells: 7.5%, p < 0.001) in bone marrow obtained from EX rats, whereas no FHL2 was revealed in SED rats. These results suggest that the mechanical impacts generated during high-intensity interval running activate a signaling pathway involving nuclear FHL2, such as that also observed with dexamethasone administration. Consequently, interval running could be proposed as a non-pharmacological strategy to contribute to bone marrow cell osteogenic differentiation.

Effect of 6-month high-impact step aerobics and resistance training on BMD and tibial bending strength in sedentary premenopausal women

The rationale of this study was to examine the effectiveness of 6-month high-impact step aerobics (SA) or moderate-intensity resistance training exercise (RT) on bone mineral density (BMD) and bone bending strength in sedentary women. Results show that SA enhanced BMD in the heel, lower leg, and lumbar spine 2.

INTRODUCTION

To determine the effectiveness of 6 months of high-impact step aerobics (SA) or moderate-intensity resistance training (RT) on areal bone mineral density (aBMD) and tibial bending strength in sedentary premenopausal women.

METHODS

Sixty-nine women (20-35 years old) who were randomly assigned to RT (n = 22), SA (n = 26), or non-treatment control (CON, n = 21) groups completed the study. SA had a minimum of 50 high-impact landings each training session. RT had a periodized lower body resistance training program incorporating eight exercises (65-85% of 1 repetition maximum: 1-RM). Both RT and SA met 3 times weekly. aBMD was assessed using dual X-ray absorptiometry (DXA). Tibial bending strength was assessed using mechanical response tissue analysis (MRTA). Measurements at 6 months were compared to baseline using ANCOVA, adjusted for baseline measures and covariates with α = 0.05.

RESULTS

Calcaneus aBMD (0.0176 vs -0.0019 or -0.0009 g/cm² relative to RT, p < 0.004, and CON, p < 0.006, respectively), lower leg aBMD (0.0105 vs -0.0036 g/cm², relative to RT, p = 0.02), and lumbar spine 2 (L2) aBMD (0.0082 vs -0.0157 g/cm² relative to CON, p < 0.02) were significantly greater in the SA group after 6 months. Tibial bending strength and bone resorption biomarkers were unchanged in all three groups after 6 months.

CONCLUSION

Sedentary premenopausal women engaging in 6 months of high-impact aerobic exercise improved aBMD in the calcaneus, lower leg, and L2.

COMPARISON OF BONE PARAMETERS BY BODY REGION IN UNIVERSITY ATHLETES: SYSTEMATIC REVIEW

ABSTRACT Introduction: Bone mineral density (BMD) and bone mineral content (BMC) vary depending on the type of sport practiced and the body region, and their measurement can be an effective way to predict health risks throughout an athlete’s life. Objective: To describe the methodological aspects (measurement of bone parameters, body regions, precision errors and covariates) and to compare BMD and BMC by body region (total body, upper limbs, lower limbs and trunk) among university athletes practicing different sports. Methods: A search was performed on the databases PubMed, Web of Science, Scopus, ScienceDirect, EBSCOhost, SportDiscus, LILACS and SciELO. Studies were selected that: (1) compared BMD and BMC of athletes practicing at least two different sports (2) used dual-energy X-ray absorptiometry (DXA) to assess bone parameters (3) focused on university athletes. The extracted data were: place of study, participant selection, participants’ sex, sport practiced, type of study, bone parameters, DXA model, software used, scan and body regions, precision error, precision protocol, covariates and comparison of bone parameters between different sports by body region. Results: The main results were: 1) BMD is the most investigated bone parameter; 2) total body, lumbar spine and proximal femur (mainly femoral neck) are the most studied body regions; 3) although not recommended, the coefficient of variation is the main indicator of precision error; 4) total body mass and height are the most commonly used covariates; 5) swimmers and runners have lower BMD and BMC values; and 6) it is speculated that basketball players and gymnasts have greater osteogenic potential. Conclusions: Swimmers and runners should include weight-bearing exercises in their training routines. In addition to body mass and height, other covariates are important. The results of this review can help guide intervention strategies focused on preventing diseases and health problems during and after the athletic career. Level of evidence II; Systematic Review.

Combining Anthropometry and Bioelectrical Impedance to Predict Body Fat in Female Athletes

CONTEXT

Accurate methods for predicting percent body fat in female athletes are needed for those who lose weight for competition. Methods mandated by sports-governing bodies for minimal weight determination in such athletes lack validation.

OBJECTIVE

To determine whether combining anthropometry (skinfolds, SF) and bioelectrical impedance analysis (BIA) in a 3 component model (3C) would improve the prediction of percentage body fat (%Fat) in female athletes. Secondarily, the Slaughter skinfold equation was evaluated. We hypothesized that compared to outcomes for SF or BIA alone, 3C-determined %Fat would not differ from our criterion method (accuracy) and would be a stronger predictor (higher r2) of the criterion.

DESIGN

Cross sectional.

SETTING

Laboratory-based study during the pre-season for collegiate sport.

PARTICIPANTS

Female athletes (n=18 D1 NCAA) recruited from swim and gymnastic teams.

MAIN OUTCOME VARIABLES

%Fat based on a four-compartment (4C) criterion incorporating body density (air displacement plethysmography), total body water (D2O dilution), and bone mineral mass (DEXA) compared to predicted %Fat using SF alone (Slaughter equation), bioelectrical impedance analysis (single frequency for TBW estimate) and combined skinfolds and BIA (3C).

RESULTS

Regression revealed that for %Fat using the criterion 4C, the highest adjusted coefficient of determination and lowest prediction error (r2 ±standard error of estimate) was 3C (r2=0.87 ±2.8%) followed by BIA (r2=0.80 ±3.5%) and SF (r2=0.76 ± 3.8%) (for all, p<0.05). Means differed for %Fat determined using BIA (26.6 ±7.5) and 3C (25.5 ±7.2) vs. the 4C (23.5 ±7.4) (ANOVA and post hoc p<0.05). The SF estimate (24.0 +7.8) did not differ from the 4C value.

CONCLUSIONS

Combining SF and BIA might improve the prediction and lower the prediction error for determining %Fat in female athletes compared to SF or BIA separately. Regardless, the Slaughter skinfold equation appeared accurate for determining the mean %Fat in these female athletes.

Serum levels of bone formation and resorption markers in relation to vitamin D status in professional gymnastics and physically active men during upper and lower body high-intensity exercise

Purpose/introduction

To compare serum levels of bone turnover markers in athletes and non-athletes, and to evaluate the relationship between serum levels of vitamin D metabolites and exercise-induced changes in biomarker levels.

Methods

Sixteen elite male artistic gymnasts (EG; 21.4 ± 0.8 years-old) and 16 physically active men (the control group, PAM; 20.9 ± 1.2 years-old) performed lower and upper body 30-s Wingate anaerobic tests (LBWT and UBWT, respectively). For biomarker analysis, blood samples were collected before, and 5 and 30 min after exercise. Samples for vitamin D levels were collected before exercise. N-terminal propeptide of type I collagen (PINP) was analysed as a marker of bone formation. C-terminal telopeptide of type I collagen (CTX) was analysed as a marker of bone resorption.

Results

UBWT fitness readings were better in the EG group than in the PAM group, with no difference in LBWT readings between the groups. UBWT mean power was 8.8% higher in subjects with 25(OH)D₃ levels over 22.50 ng/ml and in those with 24,25(OH)₂D₃ levels over 1.27 ng/ml. Serum CTX levels increased after both tests in the PAM group, with no change in the EG group. PINP levels did not change in either group; however, in PAM subjects with 25(OH)D₃ levels above the median, they were higher than those in EG subjects.

Conclusion

Vitamin D metabolites affect the anaerobic performance and bone turnover markers at rest and after exercise. Further, adaptation to physical activity modulates the effect of anaerobic exercise on bone metabolism markers.

Bone mineral density and hip structure changes over one-year in collegiate distance runners and non-athlete controls

Modification of bone is continuous throughout life and influenced by many factors, including physical activity. This study investigated changes in areal bone mineral density (aBMD) and hip structure among male and female collegiate distance runners and non-athlete controls over 12 months. Using dual-energy x-ray absorptiometry (DXA) and hip structure analysis (HSA) software, aBMD at the posterior-anterior (PA) and lateral spine, femoral neck, total hip (TH), whole body (WB), and bone geometry at the narrow neck (NN) of the femur was measured three times over 12 months. HSA included cross-sectional area (CSA), cross-sectional moment of inertia (CSMI), and Z-section modulus (Z). Male runners had significantly higher aBMD at TH and WB and greater CSA, CSMI, and Z than male controls at the end of 12 months. Female controls had higher aBMD at the PA spine than female runners at the end of 12 months. Male runners had significant increases in aBMD at the PA (p = 0.003) and lateral spine (p = 0.002), and TH (p = 0.002), female runners had significant decreases in aBMD at TH (p = 0.015) and WB (p = 0.002), male controls had significant increases in aBMD at the PA spine (p < 0.001) and WB (p < 0.001), and female controls had significant decreases in aBMD at lateral spine and TH (p = 0.008) over the year. When applying covariates of bone-free lean mass and vitamin D, male distance runners demonstrated significant improvement in CSA (3.602 ± 0.139 vs. 3.675 ± 0.122 cm², p = 0.05), CSMI (3.324 ± 0.200 to 3.467 ± 0.212 cm⁴, p < 0.05), and Z (1.81 ± 0.08 to 1.87 ± 0.08 cm³, p = 0.05) during the study. No other changes in hip structure occurred over the year. Distance running may be beneficial to aBMD and hip structure in college-age males but not females. Further research is needed on potential influences of weight-bearing activity, energy availability, and hormonal status on aBMD and hip structure in males and females.

Relative energy deficiency in sports (RED-S): elucidation of endocrine changes affecting the health of males and females

The purpose of this review is to present a different perspective of the relative energy deficiency syndrome, to improve understanding of associated endocrine alterations, and to highlight the need for further research in this area. The term "female athlete triad" was coined over 25 years ago to describe three interrelated components: disordered eating, menstrual dysfunction, and low bone mass. The syndrome's etiology is attributed to energy intake deficiency relative to energy expenditure required for health, function, and daily living. Recently, it became clear that there was a need to broaden the term, as the disorder is not an issue of only three interrelated problems but of a whole spectrum of insults resulting from low energy availability (LEA; i.e., insufficient energy availability to cover basic physiological demands) that can potentially affect any exerciser, irrespective of gender. The new model, termed relative energy deficiency in sport (RED-S), has received greater scrutiny in sports medicine due to its effects on both health and performance in athletes of both sexes. RED-S results from low-energy diets (intentional or unintentional) and/or excessive exercise. Energy deficiency reduces hypothalamic pulsatile release of gonadotropin-releasing hormone, this impairing anterior pituitary release of gonadotropins. In women, reduced FSH and LH pulsatility produces hypoestrogenism, causing functional hypothalamic amenorrhea and decreased bone mass. In men, it reduces testosterone and negatively affects bone health. Moreover, LEA alters other hormonal pathways, causing physiological consequences, such as alteration of the thyroid hormone signaling pathways, leptin levels, carbohydrate metabolism, the growth hormone/insulin-like growth factor-1 axis, and sympathetic/parasympathetic tone. This review explains and clarifies the effects of RED-S in both sexes.

Examining Bone, Muscle and Fat in Middle-Aged Long-Term Endurance Runners: A Cross-Sectional Study

Aerobic exercise training has many known cardiovascular benefits that may promote healthy aging. It is not known if long-term aerobic exercise training is also associated with structural benefits (e.g., lower fat mass, higher areal bone mineral density (BMD) and greater muscle mass). We evaluated these parameters in middle-aged long-term endurance runners compared to sex-, age-, height-, and weight-matched non-running controls. Total and regional lean and fat mass and areal BMD were assessed by dual-energy X-ray absorptiometry. Sagittal magnetic resonance images captured the cross-sectional area and thickness of the lumbar multifidus. Runners (n = 10; all male) had a mean (standard deviation; SD) age of 49 (4) years, height of 178.9 (4.9) cm, weight of 67.8 (5.8) kg, body mass index (BMI) of 21.4 (1.4) kg/m² and had been running 82.6 (27.9) km/week for 23 (13) years. Controls (n = 9) had a mean (SD) age of 51 (5) years, height of 176.0 (5.1) cm, weight of 72.8 (7.1) kg, and BMI of 23.7 (2.1) kg/m². BMI was greater in controls (p = 0.010). When compared to controls on average, runners had a 10 percentage-point greater total body lean mass than controls (p = 0.001) and 14% greater trunk lean mass (p = 0.010), as well as less total body (8.6 kg; p < 0.001), arm (58%; p = 0.002), leg (52%; p < 0.001), trunk (73%; p < 0.001), android (91%; p < 0.001), and gynoid fat mass (64%; p < 0.001). No differences were observed between groups for BMD outcomes or multifidus size. These results underscore the benefits of endurance running to body composition that carry over to middle-age.

Contribution of High School Sport Participation to Young Adult Bone Strength

INTRODUCTION

Nearly 8 million American adolescents participate in sports. Participation declines in young adulthood.

PURPOSE

This study assessed longitudinal effects of high school sport participation and muscle power on young adult bone strength.

METHODS

Two hundred twenty-eight young adults from the Iowa Bone Development Study completed an interscholastic sport participation questionnaire. Current physical activity (PA) behaviors were assessed via questionnaire. Dual x-ray absorptiometry assessed hip areal bone mineral density and was used with hip structure analysis to estimate femoral neck section modulus and hip cross-sectional area. Peripheral quantitative computed tomography provided strength-strain index and bone strength index at 38% and 4% midshaft tibial sites, respectively. Vertical jump estimated muscle power at 17 yr. Sex-specific multiple linear regression predicted young adult bone outcomes based on sport participation groups. Mediation analysis analyzed the effects of muscle power on relationships between sport participation and bone strength.

RESULTS

At follow-up, males participating in any interscholastic sport had greater bone strength than males who did not participate in sport. The explained variability in bone outcomes was 2% to 16%. Females who participated in sports requiring muscle power had greater bone strength than females who did not participate in sports or females who participated in nonpower sports (explained variability was 4%-10%). Muscle power mediated 24.7% to 41% of the effect of sport participation on bone outcomes in males and 19.4% to 30% in females.

CONCLUSIONS

Former male interscholastic sport participants and female interscholastic power sport participants have stronger bones than peers even when adjusting for current PA. Muscle power did not fully explain differences in all bone outcomes, suggesting that sport participation has additional bone health benefits.

Exercise-based correlates to calcaneal osteogenesis produced by a chronic training intervention

Thirty workouts on a gravity-independent device (Impulse Training Systems, Newnan GA) evoked significant calcaneal bone mineral content (BMC, +29%) and density (BMD, +33%) gains. High speeds and impact loads were produced per repetition. We examined exercise performance variables from the 30-workout intervention to identify correlates to delta (∆) calcaneal BMC and BMD variance. Workouts included hip extension and seated calf press exercises done with subject's left legs. ∆ values were obtained from the first and 12th workouts for the hip extension movement, and for the first and 24th workouts for the seated calf press exercise. Per exercise the following variables were quantified: peak force (∆PF), peak acceleration (∆PA), impulse (∆I), and dwell times (∆DT). Dwell times are the elapsed time between the end of the eccentric phase, and the start of the next repetition's concentric phase. Pearson Coefficients assessed correlations between performance and criterion variables. With hip extension ∆DT calculated with data from the first and 12th workouts, there were significant correlations with calcaneal ∆BMC (r = -0.64) and ∆BMD (r = -0.63). With seated calf press ∆DT derived as the difference from the first and 24th workouts, there was a significant correlation with calcaneal ∆BMC (r = -0.48), but only a trend (r = -0.45) with ∆BMD as the criterion. No other variables correlated with significant amounts of calcaneal ∆BMC and ∆BMD variance. Negative correlations infer shorter dwell times evoked greater gains. The gravity-independent device warrants continued inquiry to treat and abate calcaneal losses.

Site-Specific Load-Induced Expansion of Sca-1+Prrx1+ and Sca-1-Prrx1+ Cells in Adult Mouse Long Bone Is Attenuated With Age

Aging is associated with significant bone loss and increased fracture risk, which has been attributed to a diminished response to anabolic mechanical loading. In adults, skeletal progenitors proliferate and differentiate into bone‐forming osteoblasts in response to increasing mechanical stimuli, though the effects of aging on this response are not well‐understood. Here we show that both adult and aged mice exhibit load‐induced periosteal bone formation, though the response is significantly attenuated with age. We also show that the acute response of adult bone to loading involves expansion of Sca‐1⁺Prrx1⁺ and Sca‐1⁻Prrx1⁺ cells in the periosteum. On the endosteal surface, loading enhances proliferation of both these cell populations, though the response is delayed by 2 days relative to the periosteal surface. In contrast to the periosteum and endosteum, the marrow does not exhibit increased proliferation of Sca‐1⁺Prrx1⁺ cells, but only of Sca‐1⁻Prrx1⁺ cells, underscoring fundamental differences in how the stem cell niche in distinct bone envelopes respond to mechanical stimuli. Notably, the proliferative response to loading is absent in aged bone even though there are similar baseline numbers of Prrx1 + cells in the periosteum and endosteum, suggesting that the proliferative capacity of progenitors is attenuated with age, and proliferation of the Sca‐1⁺Prrx1⁺ population is critical for load‐induced periosteal bone formation. These findings provide a basis for the development of novel therapeutics targeting these cell populations to enhance osteogenesis for overcoming age‐related bone loss. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Sport and Triad Risk Factors Influence Bone Mineral Density in Collegiate Athletes

PURPOSE

Athletes in weight-bearing sports may benefit from higher bone mineral density (BMD). However, some athletes are at risk for impaired BMD with female athlete triad (Triad). The purpose of this study is to understand the influence of sports participation and Triad on BMD. We hypothesize that athletes in high-impact and multidirectional loading sports will have highest BMD, whereas nonimpact and low-impact sports will have lowest BMD. Triad risk factors are expected to reduce BMD values independent of sports participation.

METHODS

Two hundred thirty-nine female athletes participating in 16 collegiate sports completed dual-energy x-ray absorptiometry (DXA) scans to measure BMD z-scores of the lumbar spine (LS) and total body (TB). Height and weight were measured to calculate body mass index (BMI). Triad risk assessment variables were obtained from preparticipation examination. Mean BMD z-scores were compared between sports and by sport category (high-impact, multidirectional, low-impact, and nonimpact). Multivariable regression analyses were performed to identify differences of BMD z-scores accounting for Triad and body size/composition.

RESULTS

Athlete populations with lowest average BMD z-scores included synchronized swimming (LS, -0.34; TB, 0.21) swimming/diving (LS, 0.34; TB, -0.06), crew/rowing (LS, 0.27; TB, 0.62), and cross-country (LS, 0.29; TB, 0.91). Highest values were in gymnastics (LS, 1.96; TB, 1.37), volleyball (LS, 1.90; TB, 1.74), basketball (LS, 1.73; TB, 1.99), and softball (LS, 1.68; TB, 1.78). All Triad risk factors were associated with lower BMD z-scores in univariable analyses; only low BMI and oligomenorrhea/amenorrhea were associated in multivariable analyses (all P < 0.05). Accounting for Triad risk factors and body size/composition, high-impact sports were associated with higher LS and TB BMD z-scores and nonimpact sports with lower LS and TB BMD z-scores compared to low-impact sport (all P < 0.05).

CONCLUSIONS

Both sport type and Triad risk factors influence BMD. Athletes in low-impact and nonimpact sports and athletes with low BMI and oligomenorrhea/amenorrhea are at highest risk for reduced BMD.

Transwomen in elite sport: scientific and ethical considerations

The inclusion of elite transwomen athletes in sport is controversial. The recent International Olympic Committee (IOC) (2015) guidelines allow transwomen to compete in the women's division if (amongst other things) their testosterone is held below 10 nmol/L. This is significantly higher than that of cis-women. Science demonstrates that high testosterone and other male physiology provides a performance advantage in sport suggesting that transwomen retain some of that advantage. To determine whether the advantage is unfair necessitates an ethical analysis of the principles of inclusion and fairness. Particularly important is whether the advantage held by transwomen is a tolerable or intolerable unfairness. We conclude that the advantage to transwomen afforded by the IOC guidelines is an intolerable unfairness. This does not mean transwomen should be excluded from elite sport but that the existing male/female categories in sport should be abandoned in favour of a more nuanced approach satisfying both inclusion and fairness.

Bone Accrual in Children and Adolescent Nonelite Swimmers: A 2-Year Longitudinal Study

OBJECTIVE

To examine differences in bone mass between children and adolescents swimming competitively at nonelite levels (locally and regionally) and nonathletes and to assess changes in bone mass in these 2 groups over 24 months after taking into consideration several known confounders of bone mass.

DESIGN

Observational prospective study.

PARTICIPANTS

White nonelite swimmers (n = 128) and nonathletes (n = 106) 8 to 18 years of age from Memphis, Tennessee, USA.

MAIN OUTCOME MEASURES

Participants underwent dual-energy x-ray absorptiometry to assess total body and hip bone mineral content (BMC) at baseline and 12 and 24 months later.

RESULTS

At baseline, swimmers had 4.2% and 6.1% higher adjusted BMC for the total body and hip, respectively, compared with nonathletes (P values < 0.027). Averaging across assessment points, swimmers had 73.5 and 2.2 g higher BMC for the total body and hip, respectively, than nonathletes. Although there was a significant annual increase in total body and hip BMC in both groups (33.5 and 0.7 g, respectively), there was no difference in annualized bone accrual between swimmers and nonathletes for either total body BMC (swim by time effect; P = 0.213) or hip BMC (P = 0.265).

CONCLUSIONS

Competitive swimming at nonelite levels during childhood and adolescence does not seem to compromise bone accrual.

Impact of a Professional Nutrition Program on a Female Cross Country Collegiate Athlete: A Case Report

Low caloric intake or excessive energy expenditure can lead to a negative energy balance, which, in female athletes, may result in a condition called the female athlete triad. While several guidelines identified proper nutrition as a first line of treatment, little research has been reported to show the effect of a professional nutrition program (PNP) on the female athlete triad. The purpose of this case report was to measure the short- and long-term effects of a PNP on a female athlete presenting triad characteristics. A 20-year-old female track-and-field athlete at a Division I university who was in negative energy balance and amenorrheic underwent a one-month PNP. Short- and long-term effects measured by a dual X-ray absorptiometry scan prior to and after attending a PNP showed increased total energy intake from 2188 kcals to 3187 kcals, which resulted in an increase in body fat percent (BF%) from 4.7% to 6.7%. However, by the end of four months, energy intake and BF% (5.7% and 6.0%) values were reduced, respectively. After the twelve-month follow-up, BF% was increased (10.5%), suggesting that increasing energy intake to meet energy demands, without compromising athletic training, can be an effective treatment for the female athlete triad.

Specific Modulation of Vertebral Marrow Adipose Tissue by Physical Activity

Marrow adipose tissue (MAT) accumulation with normal aging impacts the bone, hemopoiesis, and metabolic pathways. We investigated whether exercise was associated with lower MAT, as measured by vertebral marrow fat fraction (VFF) on magnetic resonance imaging. A total of 101 healthy individuals (54 females) aged 25 to 35 years without spine or bone disease but with distinct exercise histories were studied. Long-distance runners (67 km/wk, n = 25) exhibited lower mean lumbar VFF (27.9% [8.6%] versus 33.5% [6.0%]; p = 0.0048) than non-sporting referents (n = 24). In habitual joggers (28 km/wk, n = 30), mean lumbar VFF was 31.3% (9.0%) (p = 0.22 versus referents) and 6.0 percentage points lower than referents at vertebrae T₁₀ , T₁₁ , and T₁₂ (p ≤ 0.023). High-volume road cycling (275 km/wk, n = 22) did not impact VFF. 3D accelerations corresponding to faster walking, slow jogging, and high-impact activities correlated with lower VFF, whereas low-impact activities and sedentary time correlated with higher mean lumbar VFF (all p ≤ 0.05). Given an estimated adipose bone marrow conversion of 7% per decade of life, long distance runners, with 5.6 percentage points lower VFF, showed an estimated 8-year younger vertebral marrow adipose tissue phenotype. Regression analysis showed a 0.7 percentage point reduction in mean lumbar VFF with every 9.4 km/wk run (p = 0.002). This study presents the first evidence in humans or animals that specific volumes and types of exercise may influence the age-determined adipose marrow conversion and result in low MAT. These results identify a potentially modifiable risk factor for prevalent chronic conditions related to bone metabolism, hemopoietic production, and other metabolic functions with potential global health applications. © 2017 American Society for Bone and Mineral Research.

Mechanically induced Ca2+ oscillations in osteocytes release extracellular vesicles and enhance bone formation

The vast osteocytic network is believed to orchestrate bone metabolic activity in response to mechanical stimuli through production of sclerostin, RANKL, and osteoprotegerin (OPG). However, the mechanisms of osteocyte mechanotransduction remain poorly understood. We've previously shown that osteocyte mechanosensitivity is encoded through unique intracellular calcium (Ca2+) dynamics. Here, by simultaneously monitoring Ca2+ and actin dynamics in single cells exposed to fluid shear flow, we detected actin network contractions immediately upon onset of flow-induced Ca2+ transients, which were facilitated by smooth muscle myosin and further confirmed in native osteocytes ex vivo. Actomyosin contractions have been linked to the secretion of extracellular vesicles (EVs), and our studies demonstrate that mechanical stimulation upregulates EV production in osteocytes through immunostaining for the secretory vesicle marker Lysosomal-associated membrane protein 1 (LAMP1) and quantifying EV release in conditioned medium, both of which are blunted when Ca2+ signaling was inhibited by neomycin. Axial tibia compression was used to induce anabolic bone formation responses in mice, revealing upregulated LAMP1 and expected downregulation of sclerostin in vivo. This load-related increase in LAMP1 expression was inhibited in neomycin-injected mice compared to vehicle. Micro-computed tomography revealed significant load-related increases in both trabecular bone volume fraction and cortical thickness after two weeks of loading, which were blunted by neomycin treatment. In summary, we found mechanical stimulation of osteocytes activates Ca2+-dependent contractions and enhances the production and release of EVs containing bone regulatory proteins. Further, blocking Ca2+ signaling significantly attenuates adaptation to mechanical loading in vivo, suggesting a critical role for Ca2+-mediated signaling in bone adaptation.

Bone mineral density in pre-professional female ballet dancers: A systematic review and meta-analysis

OBJECTIVES

To quantitatively compare bone mineral density (BMD) outcomes between pre-professional female adolescent ballet dancers and control populations.

DESIGN

Systematic review and meta-analysis.

METHODS

Six electronic databases and relevant journals were systematically searched up to August 2017. Included articles examined BMD in adolescent females undergoing pre-professional ballet training and healthy age-matched controls with an available English full text. Dancers were aged 15-19 years and trained in ballet at least 10h per week. BMD data were analysed via standardized mean difference to account for differences in reporting methods RESULTS: From 3984 potential articles, 8 cross-sectional studies were accepted for inclusion, which compared 293 dancers (16.9±0.8 years) to 333 controls (16.9±0.9 years). No data were available from longitudinal studies. Dancers displayed lower BMD at the radius and higher BMD at the femoral neck, femoral trochanter and Ward's triangle. No significant differences were observed in the lumbar spine or tibia. The overall study quality was low and heterogeneity was present in some analyses.

CONCLUSIONS

This meta-analysis indicates that there may be a site-specific osteogenic effect of pre-professional classical ballet training in adolescent females, with a notable and concerning finding of reduced upper limb BMD compared to age-matched controls. Longitudinal cohort studies are required to confirm the effects of pre-professional ballet training on BMD during adolescence.

Strain and Vibration in Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are multipotent cells capable of differentiating into any mesenchymal tissue, including bone, cartilage, muscle, and fat. MSC differentiation can be influenced by a variety of stimuli, including environmental and mechanical stimulation, scaffold physical properties, or applied loads. Numerous studies have evaluated the effects of vibration or cyclic tensile strain on MSCs towards developing a mechanically based method of differentiation, but there is no consensus between studies and each investigation uses different culture conditions, which also influence MSC fate. Here we present an overview of the response of MSCs to vibration and cyclic tension, focusing on the effect of various culture conditions and strain or vibration parameters. Our review reveals that scaffold type (e.g., natural versus synthetic; 2D versus 3D) can influence cell response to vibration and strain to the same degree as loading parameters. Hence, in the efforts to use mechanical loading as a reliable method to differentiate cells, scaffold selection is as important as method of loading.

Swimming and peak bone mineral density: A systematic review and meta-analysis

This meta-analysis aims to determine the effects of regular swimming on bone mineral density (BMD) in young adults (18-30 years). A systematic search was performed in Pubmed, SPORTDiscus and the Cochrane Library from the earliest possible year to March 2016. Swimmers were compared to non-athletic controls (CG) and to high-impact athletes (HIGH). Effect sizes with the Hedges g in random effects models were developed. Fourteen studies met the inclusion criteria and were included in the meta-analyses. Swimmers presented similar BMD values to CG in whole-body (g = -0.20; P = 0.251), femoral neck (g = -0.05; P = 0.818) and lumbar spine (g = 0.18; P = 0.492); and lower BMD in the whole-body (g = -1.21; P < 0.001), femoral neck (g = -1.51; P < 0.001) and lumbar spine (g = -0.84; P = 0.017) than the HIGH. For the whole-body differences, the higher the latitude the smaller the differences between swimmers and HIGH (B = 0.10; P = 0.001). For the femoral neck differences, age also seemed to reduce the differences between groups (B = 0.19; P = 0.020). Young adult swimmers present similar BMD values than CG and lower values than HIGH.

Effects of water-based exercise on bone health of middle-aged and older adults: a systematic review and meta-analysis

BACKGROUND

Age-related bone loss is a major health concern. Only exercises associated with high-impact and mechanical loading have been linked to a positive effect on bone turnover; however, these types of exercises may not always be appropriate for middle-aged and older adults due to physical decline or chronic disorders such as osteoarthritis. Water-based exercise (WBE) has been shown to affect different components of physical fitness, has lower risks of traumatic fracture, and applies less stress to joints. However, the effects of WBE on bone health are unclear.

OBJECTIVE

This study aimed to explore whether WBE is effective in preventing age-related bone deterioration in middle-aged and older adults.

METHODS

A search of relevant databases and the references of identified studies was performed. Critical narrative synthesis and meta-analyses were conducted.

RESULTS

Eleven studies, involving 629 participants, met all inclusion criteria. All participants were postmenopausal women. Eight studies compared WBE to a sedentary control group, and four studies had land-based exercise (LBE) participants as a comparison group. Meta-analyses revealed significant differences between WBE and control group in favor of WBE for changes in bone mineral density (BMD) at the lumbar spine (mean difference [MD] 0.03 g/cm²; 95% confidence interval [CI]: 0.01 to 0.05) and femoral neck (MD 0.04 g/cm²; 95% CI: 0.02 to 0.07). Significant differences were also revealed between WBE and LBE in favor of LBE for changes in lumbar spine BMD (MD -0.04 g/cm²; 95% CI: -0.06 to -0.02). However, there was no significant difference between WBE and LBE for changes in femoral neck BMD (MD -0.03 g/cm²; 95% CI: -0.08 to 0.01).

CONCLUSION

WBE may have benefits with respect to maintaining or improving bone health in postmenopausal women but less benefit when compared to LBE. Further research is required on this topic.

Impact sports and bone fractures among adolescents

The objective of the present study was to investigate the effects of different sports on stress fractures among adolescents during a 9-month follow-up period. The sample was composed of 184 adolescents divided into three groups (impact sports [n = 102]; swimming [n = 35]; non-sports [n = 47]). The occurrence of stress fracture was reported by participants and coaches. As potential confounders we considered age, sex, resistance training, body composition variables and age at peak of height velocity. There were 13 adolescents who reported fractures during the 9-month period. Bone mineral density values were higher in adolescents engaged in impact sports (P-value = 0.002). Independently of confounders, the risk of stress fracture was lower in adolescents engaged in impact sports than in non-active adolescents (hazard ratio [HR] = 0.23 [95% confidence interval (CI) = 0.05 to 0.98]), while swimming practice was not associated to lower risk of fracture (HR = 0.49 [95% CI = 0.09 to 2.55]). In conclusion, the findings from this study indicate the importance of sports participation among adolescents in the reduction of stress fracture risk, especially with impact sports. More importantly, these results could be relevant for recognising adolescents in danger of not reaching their potential for peak bone mass and later an increased risk of fractures.

No difference in the level of physical activity between children who have or have never sustained a fracture

This study investigates whether children with an acute fracture have a different level of physical activity compared to children who have never sustained a fracture, as measured by the Physical Activity Questionnaire for older children (PAQ-C). The PAQ-C scores of 683 children (295 girls) aged 6-12 years (mean age 9.4 years) who presented to our institution with an acute fracture were compared to the PAQ-C scores of 151 random children (81 girls) aged 6-12 years (mean 9.1 years) in the same area who had never sustained a fracture. Multivariate regression analysis was employed, controlling for age and gender. The mean PAQ-C score of the children who presented to the institution with an acute fracture was 2.85 (95% confidence interval [CI], 2.80-2.91). For the children who had never sustained a fracture, the mean PAQ-C score was 2.78 (95% CI, 2.69-2.87). If there is a true difference in the level of physical activity between children who have or have never sustained a fracture, the PAQ-C questionnaire is not sensitive enough to identify it.

Prolonged Practice of Swimming Is Negatively Related to Bone Mineral Density Gains in Adolescents

BACKGROUND

The practice of swimming in "hypogravity" conditions has potential to decrease bone formation because it decreases the time engaged in weight-bearing activities usually observed in the daily activities of adolescents. Therefore, adolescents competing in national levels would be more exposed to these deleterious effects, because they are engaged in long routines of training during most part of the year. To analyze the effect of swimming on bone mineral density (BMD) gain among adolescents engaged in national level competitions during a 9-month period.

METHODS

Fifty-five adolescents; the control group contained 29 adolescents and the swimming group was composed of 26 athletes. During the cohort study, BMD, body fat (BF) and fat free mass (FFM) were assessed using a dual-energy x-ray absorptiometry scanner. Body weight was measured with an electronic scale, and height was assessed using a stadiometer.

RESULTS

During the follow-up, swimmers presented higher gains in FFM (Control 2.35 kg vs. Swimming 5.14 kg; large effect size [eta-squared (ES-r)=0.168]) and BMD-Spine (Swimming 0.087 g/cm(2) vs. Control 0.049 g/cm(2); large effect size [ES-r=0.167]) compared to control group. Male swimmers gained more FFM (Male 10.63% vs. Female 3.39%) and BMD-Spine (Male 8.47% vs. Female 4.32%) than females. Longer participation in swimming negatively affected gains in upper limbs among males (r=-0.438 [-0.693 to -0.085]), and in spine among females (r=-0.651 [-0.908 to -0.036]).

CONCLUSIONS

Over a 9-month follow-up, BMD and FFM gains were more evident in male swimmers, while longer engagement in swimming negatively affected BMD gains, independently of sex.

The Female Athlete Triad

The number of girls participating in sports has increased significantly since the introduction of Title XI in 1972. As a result, more girls have been able to experience the social, educational, and health-related benefits of sports participation. However, there are risks associated with sports participation, including the female athlete triad. The triad was originally recognized as the interrelationship of amenorrhea, osteoporosis, and disordered eating, but our understanding has evolved to recognize that each of the components of the triad exists on a spectrum from optimal health to disease. The triad occurs when energy intake does not adequately compensate for exercise-related energy expenditure, leading to adverse effects on reproductive, bone, and cardiovascular health. Athletes can present with a single component or any combination of the components. The triad can have a more significant effect on the health of adolescent athletes than on adults because adolescence is a critical time for bone mass accumulation. This report outlines the current state of knowledge on the epidemiology, diagnosis, and treatment of the triad conditions.

A review of the effect of swim training and nutrition on bone mineral density in female athletes

PURPOSE

The present paper reviews the physiological adaptation to swim training and dietary supplementation relating to bone mineral density (BMD) in female swimmers. Swim training still seems to have conflicting effects on bone health maintenance in athletes.

METHODS

This review article focuses on swim training combined with dietary supplementation with respect to BMD in female athletes.

RESULTS

Upon review of previous studies, it became obvious that the majority of studies did not collect physical activity data on the swimmers outside of their swimming activities. These activities may have some influence on the BMD of swimmers and therefore, future studies need to examine additional physical activity history data as well as swim training. This additional information may help to explain why swimmers' BMD tends to be lower than the BMD of control individuals in many studies. Moreover, dietary supplementation such as calcium, magnesium, and vitamin D also affect bone health in swimmers, and it is extremely important to evaluate BMD in the context of dietary supplementation.

CONCLUSION

A review of the literature suggests that exercise intervention studies, including longitudinal and randomized control trials, need to attempt to introduce various exercise programs to female swimmers in order to determine the optimal exercise prescription for bone health.

Comparisons of Bone Mineral Density Between Recreational and Trained Male Road Cyclists

OBJECTIVE

To compare measures of training, performance, body composition, and areal bone mineral density (aBMD) between age-matched recreational and competitively trained male road cyclists.

DESIGN

Cross-sectional.

SETTING

Laboratory.

PARTICIPANTS

Male cyclists (N = 28) aged 21-54 years riding more than 3 hours per week.

ASSESSMENT OF RISK FACTORS

Men who train at high (≥8 h/wk) and moderate volumes (3-8 h/wk).

MAIN OUTCOME MEASURES

Areal bone mineral density assessments by dual energy x-ray absorptiometry of the whole body, lumbar spine (L1-L4), right and left hips, maximal oxygen uptake (V[Combining Dot Above]O2max), and training history.

RESULTS

Trained cyclists had higher power to weight (5.3 ± 0.4 vs 4.7 ± 0.3 W/kg, P = 0.001), V[Combining Dot Above]O2max (57.2 ± 4.5 vs 53.0 ± 6.1 mL·kg·min, P = 0.049) and training volume (10.6 ± 2.1 vs 6.3 ± 0.9 h/wk, P < 0.001) than recreational cyclists. Trained cyclists had lower right (0.898 ± 0.090 vs 0.979 ± 0.107 g/cm, P = 0.047) and left hip aBMD (0.891 ± 0.079 vs 0.973 ± 0.104 g/cm, P = 0.032). Z-scores identified lumbar (L1-L4) aBMD as osteopenic (-2.5 < Z-score < -1.0) in trained cyclists (-1.39 ± 1.09). Lumbar scans identified 12 trained and 4 recreational cyclists as osteopenic and 3 trained cyclists as osteoporotic.

CONCLUSIONS

Areal bone mineral density is lower in trained male road cyclists compared with recreational, specifically at the hips. Lumbar aBMD is low in both trained and recreational cyclists. Research is needed to determine the chronic effects of cycling on aBMD and interventions that improve aBMD in this population.

CLINICAL RELEVANCE

This study suggests road cycling may compromise aBMD and potentially increase the likelihood of low-trauma fractures; health care professionals should consider this exposure when exercise prescriptions are designed for patients at-risk for osteopenia/osteoporosis, for example, women and older adults.

Peak-bone-mass development in young adults: effects of study program related levels of occupational and leisure time physical activity and exercise. A prospective 5-year study

SUMMARY

Young adulthood is characterized by profound life-style changes. This study suggests that reduction of sport or exercise, induced by alteration of the occupational situation, negatively impacts generation/maintenance of peak bone mass. In order to compensate occupational-related reductions of physical activity, workplace exercise programs will be helpful.

INTRODUCTION

Only few studies have determined the effect of physical activity or physical exercise on bone mineral density (BMD) in the period of late skeletal maturation, i.e. around peak bone mass. The aim of this article was to determine the long-term effect of different levels of physical activity and exercise directly and indirectly derived by occupation during young adulthood.

METHODS

Sixty-one male and female dental students (DES) and 53 male and female sport students (SPS) 21±2 years old were accompanied over the course (4.8±0.5 years) of their study program. BMD at the lumbar spine (LS), hip, and whole body (WB) were determined using dual-energy X-ray absorptiometry.

RESULTS

Parameters of physical activity increased non-significantly in both groups with no relevant differences between the groups. Indices of exercise, however, increased significantly in the SPS group while a significant decrease was assessed for the DES group. Independent of gender, BMD of the SPS increased significantly (p≤0.007) at all skeletal sites (LS, 2.4±3.9%; hip, 1.6±3.5%; WB, 1.8±2.8%) while BMD of the DES remained unchanged at LS (-0.6±4.4%, p=0.432) and WB (0.5±1.9%, p=0.092) but decreased significantly at the hip (-1.9±4.3%, p=0.010). BMD-changes at LS, hip, and WB differ significantly between SPS and DES (p≤0.017). Results remained unchanged after adjusting for baseline BMD-values that differed (p=0.030 to p=0.082) in favor of the SPS group.

CONCLUSION

Changes of exercise levels directly or indirectly caused by occupational factors during young adulthood significantly affected generation and/or maintenance of peak bone mass. Compensatory exercise is thus highly relevant for bone health of young adults.

Weight loss and bone mineral density

PURPOSE OF REVIEW

Despite evidence that energy deficit produces multiple physiological and metabolic benefits, clinicians are often reluctant to prescribe weight loss in older individuals or those with low bone mineral density (BMD), fearing BMD will be decreased. Confusion exists concerning the effects that weight loss has on bone health.

RECENT FINDINGS

Bone density is more closely associated with lean mass than total body mass and fat mass. Although rapid or large weight loss is often associated with loss of bone density, slower or smaller weight loss is much less apt to adversely affect BMD, especially when it is accompanied with high intensity resistance and/or impact loading training. Maintenance of calcium and vitamin D intake seems to positively affect BMD during weight loss. Although dual energy X-ray absorptiometry is normally used to evaluate bone density, it may overestimate BMD loss following massive weight loss. Volumetric quantitative computed tomography may be more accurate for tracking bone density changes following large weight loss.

SUMMARY

Moderate weight loss does not necessarily compromise bone health, especially when exercise training is involved. Training strategies that include heavy resistance training and high impact loading that occur with jump training may be especially productive in maintaining, or even increasing bone density with weight loss.

Moderate intensity resistive exercise improves metaphyseal cancellous bone recovery following an initial disuse period, but does not mitigate decrements during a subsequent disuse period in adult rats

Spaceflight provides a unique environment for skeletal tissue causing decrements in structural and densitometric properties of bone. Previously, we used the adult hindlimb unloaded (HU) rat model to show that previous exposure to HU had minimal effects on bone structure after a second HU exposure followed by recovery. Furthermore, we found that the decrements during second HU exposure were milder than the initial HU cycle. In this study, we used a moderate intensity resistance exercise protocol as an anabolic stimulus during recovery to test the hypothesis that resistance exercise following an exposure to HU will significantly enhance recovery of densitometric, structural, and, more importantly, mechanical properties of trabecular and cortical bone. We also hypothesized that resistance exercise during recovery, and prior to the second unloading period, will mitigate the losses during the second exposure. The hypothesis that exercise during recovery following hindlimb unloading will improve bone quality was supported by our data, as total BMC, total vBMD, and cancellous bone formation at the proximal tibia metaphysis increased significantly during exercise period, and total BMC/vBMD exceeded age-matched control and non-exercised values significantly by the end of recovery. However, our results did not support the hypothesis that resistance exercise prior to a subsequent unloading period will mitigate the detrimental effects of the second exposure, as the losses during the second exposure in total BMC, total vBMD, and cortical area at the proximal tibia metaphysis for the exercised animals were similar to those of the non-exercised group. Therefore, exercise did not mitigate effects of the second HU exposure in terms of pre-to-post HU changes in these variables, but it did produce beneficial effects in a broader sense.

Ground reaction forces and osteogenic index of the sport of cyclocross

Weight-bearing activity has been shown to increase bone mineral density. Our purpose was to measure vertical ground reaction forces (GRFs) during cyclocross-specific activities and compute their osteogenic index (OI). Twenty-five healthy cyclocross athletes participated. GRF was measured using pressure-sensitive insoles during seated and standing cycling and four cyclocross-specific activities: barrier flat, barrier uphill, uphill run-up, downhill run-up. Peak and mean GRF values, according to bodyweight, were determined for each activity. OI was computed using peak GRF and number of loading cycles. GRF and OI were compared across activities using repeated-measures ANOVA. Number of loading cycles per activity was 6(1) for barrier flat, 8(1) barrier uphill, 7(1) uphill run-up, 12(3) downhill run-up. All activities had significantly (P < 0.01) higher peak GRF, mean GRF values and OI when compared to both seated and standing cycling. The barrier flat condition (P < 0.01) had highest peak (2.9 times bodyweight) and mean GRF values (2.3 times bodyweight). Downhill run-up (P < 0.01) had the highest OI (6.5). GRF generated during the barrier flat activity is similar in magnitude to reported GRFs during running and hopping. Because cyclocross involves weight bearing components, it may be more beneficial to bone health than seated road cycling.

Odd-impact loading results in increased cortical area and moments of inertia in collegiate athletes

PURPOSE

The purpose of this study was to investigate tibial changes in volumetric bone mineral density and geometry that take place in athletes from pre- to post-season.

METHODS

Female college athletes (n = 36) and ten controls recruited from the student population were included in the study. Participants had their left tibia scanned by pQCT at 4, 20, and 66 % of the overall length from the distal end before and after their competitive seasons. Subjects were divided into four groups: non-athlete (controls, n = 10), moderate-impact (cross-country runners, n = 13), high-impact (volleyball and basketball, n = 11), and odd-impact (soccer, n = 12).

RESULTS

Anterior-posterior and medial-lateral diameter increased at the 4 % site in control subjects. In the moderate-impact group, medial-lateral moment of inertia (MOI) increased by 1.2 ± 1.8 (mean ± SD) percent at the 20 % site. In high-impact group, anterior-posterior MOI increased by 1.6 ± 2.0 percent at the 66 % site. In odd-impact group, cortical area (1.4 ± 2.3 %) and cortical thickness (1.8 ± 2.8 %) increased at the 20 % site increased, as did the polar MOI (1.8 ± 2.2 %) at the 66 % site.

CONCLUSIONS

Load-specific changes resulting in improved measures of bone strength take place in athletes during a competitive season. These changes may result in improved resistance to fractures and stress fractures.

The Contribution of Experimental in vivo Models to Understanding the Mechanisms of Adaptation to Mechanical Loading in Bone

Changing loading regimens by natural means such as exercise, with or without interference such as osteotomy, has provided useful information on the structure:function relationship in bone tissue. However, the greatest precision in defining those aspects of the overall strain environment that influence modeling and remodeling behavior has been achieved by relating quantified changes in bone architecture to quantified changes in bones' strain environment produced by direct, controlled artificial bone loading. Jiri Hert introduced the technique of artificial loading of bones in vivo with external devices in the 1960s using an electromechanical device to load rabbit tibiae through transfixing stainless steel pins. Quantifying natural bone strains during locomotion by attaching electrical resistance strain gages to bone surfaces was introduced by Lanyon, also in the 1960s. These studies in a variety of bones in a number of species demonstrated remarkable uniformity in the peak strains and maximum strain rates experienced. Experiments combining strain gage instrumentation with artificial loading in sheep, pigs, roosters, turkeys, rats, and mice has yielded significant insight into the control of strain-related adaptive (re)modeling. This diversity of approach has been largely superseded by non-invasive transcutaneous loading in rats and mice, which is now the model of choice for many studies. Together such studies have demonstrated that over the physiological strain range, bone's mechanically adaptive processes are responsive to dynamic but not static strains; the size and nature of the adaptive response controlling bone mass is linearly related to the peak loads encountered; the strain-related response is preferentially sensitive to high strain rates and unresponsive to static ones; is most responsive to unusual strain distributions; is maximized by remarkably few strain cycles, and that these are most effective when interrupted by short periods of rest between them.

Bone micro-architecture, estimated bone strength, and the muscle-bone interaction in elite athletes: an HR-pQCT study

Athletes participating in sports characterized by specific loading modalities have exhibited different levels of augmentation of bone properties; however, the extent to which these loading environments affect bone micro-architecture and estimated bone strength (i.e., bone quality) remains unclear. Furthermore, the relative role of impact loading versus loading due to muscle forces in determining bone properties is confounded. The objectives of this study were 1) to examine the role of impact loading on bone quality of the distal radius and distal tibia in elite athletes, as determined by high resolution peripheral quantitative computed tomography (HR-pQCT) and finite element analysis (FEA), and 2) to investigate the relationship between bone quality and muscle strength in elite athletes. Ninety-five females (n=59) and males (n=36) between the ages of 16-30 years participated in the study. Participants included alpine skiers (high-impact), soccer players (moderate impact), swimmers (low-impact), and non-athletic controls. All group comparisons were made after accounting for age, height, and body mass. As expected, minimal differences in HR-pQCT parameters across groups were observed at the non weight-bearing distal radius. At the weight-bearing distal tibia, female alpine skiers and soccer players had significantly higher bone density, cortical thickness, and failure load (i.e., bone strength (N) in compression estimated by FEA) than swimmers (p<0.05). Female alpine skiers also had lower trabecular separation than swimmers and controls. Male alpine skiers had 20% higher trabecular bone mineral density than swimmers, and male soccer players exhibited 22% higher trabecular number than swimmers at the distal tibia (p<0.05). Male alpine skiers and soccer players had 28-38% higher failure load at the distal tibia than swimmers. No differences in bone parameters were observed between swimmers and controls for either sex at either site. Both muscle strength and sporting activity were predictors of failure load at the distal tibia in the female cohort. Sporting activity, but not muscle strength, was a significant predictor of failure load in the male cohort at both the radius and tibia. This data suggests that impact loading in sporting activity is highly associated with bone quality. Longitudinal and interventional studies are required to further clarify the muscle-bone interaction.

Is bone tissue really affected by swimming? A systematic review

Background

Swimming, a sport practiced in hypogravity, has sometimes been associated with decreased bone mass.

Aim

This systematic review aims to summarize and update present knowledge about the effects of swimming on bone mass, structure and metabolism in order to ascertain the effects of this sport on bone tissue.

Methods

A literature search was conducted up to April 2013. A total of 64 studies focusing on swimmers bone mass, structure and metabolism met the inclusion criteria and were included in the review.

Results

It has been generally observed that swimmers present lower bone mineral density than athletes who practise high impact sports and similar values when compared to sedentary controls. However, swimmers have a higher bone turnover than controls resulting in a different structure which in turn results in higher resistance to fracture indexes. Nevertheless, swimming may become highly beneficial regarding bone mass in later stages of life.

Conclusion

Swimming does not seem to negatively affect bone mass, although it may not be one of the best sports to be practised in order to increase this parameter, due to the hypogravity and lack of impact characteristic of this sport. Most of the studies included in this review showed similar bone mineral density values in swimmers and sedentary controls. However, swimmers present a higher bone turnover than sedentary controls that may result in a stronger structure and consequently in a stronger bone.

Peripubertal female athletes in high-impact sports show improved bone mass acquisition and bone geometry

OBJECTIVE

Intensive physical training may have a sport-dependent effect on bone mass acquisition. This cross-sectional study evaluated bone mass acquisition in girls practicing sports that put different mechanical loads on bone.

MATERIALS/METHODS

Eighty girls from 10.7 to 18.0 years old (mean 13.83 ± 1.97) were recruited: 20 artistic gymnasts (AG; high-impact activity), 20 rhythmic gymnasts (RG; medium-impact activity), 20 swimmers (SW, no-impact activity), and 20 age-matched controls (CON; leisure physical activity <3h/wk). Areal bone mineral density (aBMD) was determined using DEXA. Hip structural analysis applied at the femur evaluated cross-sectional area (CSA, cm(2)), section modulus (Z, cm(3)), and buckling ratio. Bone turnover markers and OPG/RANKL levels were analyzed.

RESULTS

AG had higher aBMD than SW and CON at all bone sites and higher values than RG in the lumbar spine and radius. RG had higher aBMD than SW and CON only in the femoral region. CSA and mean cortical thickness were significantly higher and the buckling ratio was significantly lower in both gymnast groups compared with SW and CON. In RG only, endocortical diameter and width were reduced, while Z was only increased in AG compared with SW and CON. Reduced bone remodeling was observed in RG compared with AG only when groups were subdivided according to menarcheal status. All groups showed similar OPG concentrations, while RANKL concentrations increased with age and were decreased in SW.

CONCLUSION

High-impact activity clearly had a favorable effect on aBMD and bone geometry during the growth period, although the bone health benefits seem to be more marked after menarche.