Lower limb bone mineral density (BMD) can be a critical marker of skeletal strength and injury risk, especially in female athletes engaged in high-intensity sports. Yet, the question remains: does the BMD of these athletes change significantly throughout a competitive season? Surprisingly, current research suggests that it might not, and here's where it gets controversial: some might assume that rigorous training and impact loading would noticeably increase BMD over just a few months, but evidence indicates otherwise. This is a vital area to understand for coaches, trainers, and athletes aiming to optimize performance and prevent bone injuries.
Introduction
Bone mineral density, commonly assessed through dual-energy X-ray absorptiometry (DXA), serves as a vital indicator of bone health and potential fracture risk in diverse populations.1 When BMD declines, bones become more fragile, raising the chance of fractures — which is why DXA has become the gold standard for tracking bone changes over time due to its safety and high reliability.2 While many discussions focus on age-related BMD loss and osteoporosis, maintaining strong bones early in life is just as important. Achieving peak bone mass during adolescence and early adulthood sets the foundation for skeletal integrity later in life.3–5 Furthermore, athletes with lower BMD face a higher risk of stress fractures, which can threaten their careers.6 For female athletes, monitoring bone health is especially critical because they are more vulnerable to stress fractures compared to their male counterparts,7–9 and fluctuations in BMD can reflect underlying issues such as energy deficits, poor nutrition, or excessive impact workloads.10,11
Collegiate athletes often undergo intense training regimens that involve repetitive, high-impact activities, and competitive pressures—all factors known to influence BMD.12 DXA scans can detect early signs of conditions like the female athlete triad and osteoporosis—conditions strongly linked to low BMD—with females bearing a particularly high risk.13,14 For example, a study tracking first- and second-year college athletes in basketball, soccer, and hockey observed a modest increase of about 0.05 g/cm² in lower limb BMD after one year of training, reinforcing the link between physical activity and bone adaptation.15 Nonetheless, few studies have examined how BMD changes specifically between pre- and post-season within the same athletic year, especially comparing the dominant versus nondominant limb in female athletes across different sports.15,16 And this is the part most people might overlook: whether BMD fluctuates during a single season can influence training strategies and injury prevention efforts.
Research Aim and Hypotheses
Given these points, our primary goal was to explore how lower limb BMD varies from preseason to postseason in female Division I athletes across multiple sports such as volleyball, soccer, and field hockey. We specifically aimed to see if there are differences between the dominant and nondominant limbs' BMD over this period. Our hypothesis was that measurable, albeit moderate, changes might occur in lower limb BMD within a season. Understanding whether BMD remains stable or changes during this timeframe can help coaches and health professionals develop better training protocols, proactively monitor athlete health, and ultimately reduce the risk of bone injuries.
Methods
Study Design — This investigation tracked BMD alterations using DXA scans performed before and after the athletic season in female collegiate athletes participating in field hockey, soccer, and volleyball. These sports were chosen due to their distinct loading patterns—soccer and field hockey emphasize lower-limb activity, while volleyball involves frequent jumping and landings that also heavily load the legs despite engaging upper limbs more. Preseason assessments happened just before the season started, and postseason measurements occurred shortly after the season ended—averaging about 126.5 days apart. The testing was scheduled so that athletes were scanned roughly three weeks before the season began and approximately three weeks after it concluded. All procedures conformed to ethical standards outlined in the Declaration of Helsinki.
Participants — Female Division I athletes from the university’s teams were recruited and tested at both timepoints. Specific inclusion and exclusion criteria (see Table 1) ensured consistency and safety.
DXA Scan Protocol — Whole-body scans were performed using the Hologic Horizon DXA system. Calibration was verified at each session with a phantom to ensure accuracy. Participants wore light clothing, removed metal accessories, and lay supine on the scanner with arms at their sides and legs extended in a slightly dorsiflexed (foot pointed up) position. The scans covered the entire lower limbs, segmented from the femoral neck down to toe metatarsals, enabling extraction of BMD values specifically for the dominant and nondominant limbs for each athlete.
Statistical Approach — Data were analyzed using SPSS software. Changes in demographic characteristics between preseason and postseason were tested with dependent t-tests. A two-way ANCOVA, accounting for sport type, examined the effects of time and limb on BMD, including their interaction, to determine if seasonal BMD changes differed between limbs. Significance was set at p < 0.05.
Results
The sample included 64 female athletes who completed both scans, and their demographic data are summarized in Table 2. Power analysis revealed an 84% chance of detecting meaningful differences. The key finding was that the interaction between season (pre vs. post) and limb (dominant vs. nondominant) was not statistically significant (F1,61 = 0.09, p = 0.76). This indicates that BMD changes over the season did not differ between limbs. Additionally, no main effect for time was observed (F1,61 = 0.80, p = 0.38), with approximate BMD values of 1.24 g/cm² at preseason and 1.25 g/cm² at postseason. The only significant main effect emerged for limb (F1,61 = 4.45, p = 0.04), with estimated marginal means of about 1.215 g/cm² for the nondominant and 1.217 g/cm² for the dominant limb. These minimal differences point to a relatively stable BMD throughout the season.
Discussion
Our study set out to determine whether BMD in female collegiate athletes shifts significantly over a single sports season. Contrary to our initial hypothesis that measurable BMD changes might be evident, our results showed no significant shifts from preseason to postseason. Interestingly, we did find that the dominant and nondominant limbs differ slightly in BMD, with this difference being statistically significant when controlling for sport. Nonetheless, the actual magnitude of this difference was very small, with both limbs maintaining similar BMD levels. The prominent exception was volleyball players, who showed notable asymmetry—likely due to the sport’s asymmetrical impact loading, such as frequent jumping on one leg. Volleyball athletes had higher BMD overall, highlighting how sport-specific activity patterns can influence bone adaptation.
These findings align with some prior research—such as a study on competitive cyclists that showed no significant total body BMD change over several months19—and contrast with others, particularly studies involving longer assessment periods or different sports. For example, in sports like volleyball, BMD differences between off-season, preseason, and postseason phases have been recorded, suggesting some sports may promote noticeable bone gains over time.20–22 The variability across studies underscores that the duration, type of mechanical loading, and measurement methods all influence BMD outcomes.
Given the stable BMD observed here, it’s possible that athletes start their season with already healthy bone density, and short-term training doesn’t produce large, detectable changes. The relatively brief interval between scans—roughly four months—may not suffice to detect subtle bone remodeling, emphasizing the need for longer-term studies. Extending assessments across multiple seasons could better reveal how sustained or cumulative training influences bone health.
There are some critical limitations to note. Our study lacked detailed data on nutrition, sleep, rest, or stress levels—all factors that significantly impact bone health. Additionally, differences in limb loading between sports and individual physiological factors could have affected BMD readings. Future research should incorporate comprehensive nutritional assessments, recovery behaviors, and physiological data to fully understand these influences. Recognizing these limitations can guide more targeted interventions aimed at optimizing bone strength among female athletes.
Conclusion
In summary, the BMD of lower limbs in female Division I athletes remains relatively unchanged during a competitive season. This stability might reflect adequate training protocols or simply the insufficient duration and intensity needed to produce measurable bone adaptation. As bone remodeling is a gradual process, more extended and detailed longitudinal studies are necessary. Future research integrating sport-specific factors, nutrition, recovery, and longer follow-up periods will be essential to develop better strategies for maintaining and enhancing skeletal health, ultimately helping athletes perform their best while minimizing injury risks.
Data Sharing & Ethics — Data are confidential, with all procedures approved by Michigan State University’s Institutional Review Board. Participants provided written informed consent, including consent for publication. The authors declare no conflicts of interest, and the study was funded in part by Nike, with support for Dr. Harkey from the NIAMS.
