Introduction
Bone health may be a concern in Paralympic athletes, given the blunted osteogenic stimuli in wheelchair and prostheses users, as well as potential nutritional deficiencies. However, information on the prevalence and skeletal site of low bone mineral density (BMD) is scarce. The aim of this study is to assess the BMD of Paralympic athletes from various sport disciplines.

Methods
So far, 47 Paralympic athletes (para-cycling (n=14), wheelchair tennis (n=9) wheelchair basketball (n=18) and para cross-country skiing (n=6)) have been included in this ongoing collaborative study conducted in the Netherlands and Norway. Dual-energy x-ray absorptiometry scans of the whole body (WB), spine (SP) and hip (total hip (TH) and femoral neck (FN)) were conducted and analyzed for BMD z-scores. Data are reported as mean±SD. Comparisons between groups were conducted by one-way ANOVA with Bonferroni correction.

Results
On a WB-level, 19% of all athletes had a z-score below -1.0, which is the clinical cut-off level of low BMD. When assessed at the SP, TH, and FN, the prevalence of low BMD was 20%, 30% and 36% of all athletes, respectively. At the SP, the basketball players displayed a significantly higher BMD (z-score: 1.1±1.0) compared with both the cyclists (z-score: -0.7±1.1 P<0.001) and cross-country skiers (z-score: -0.5±1.3 P=0.036), while the relatively high BMD of the SP of tennis players’ (z-score: 0.4±1.3, P=0.561) was not significantly different from other sports.  No significant differences in BMD were found between sports for either TH or FN.

Conclusion
In Paralympic athletes, low BMD appears to be particularly prevalent in TH and FN. The BMD of the SP does not seem to be compromised in wheelchair basketball and tennis players; suggesting ample osteogenic stimuli for the SP in those particular wheelchair sports. Nevertheless, BMD of TH and FN deserve attention across all Paralympic disciplines.