Bone mineral density in female high school athletes: Interactions of menstrual function and type of mechanical loading

Abstract

During adolescence, skeletal integrity of girls is largely dependent on menstrual function and impact exercise, yet currently there is limited research regarding the interaction between menstrual status and type of mechanical loading associated with various high school sports. Our purpose was to examine associations of menstrual status, type of mechanical loading, and bone mineral density (BMD) in female high school athletes participating in high/odd impact or repetitive/non-impact sport. Participants were 161 female high school athletes (15.7±1.3 years; 165.3±6.9 cm; 59.4±8.7 kg) representing high/odd impact (n=93, including soccer, softball, volleyball, tennis, lacrosse, and track sprinters and jumpers), or repetitive/non-impact sports (n=68, including swimmers, cross-country and track distance runners who participated in events ≥800 m). Areal BMD was measured by DXA at the spine (L1–L4), proximal femur, and total body. Menstrual status was determined by self-report. Athletes with primary, secondary or oligomenorrhea were combined into a single group (oligo/amenorrheic) and compared to eumenorrheic athletes. Analysis of covariance (ANCOVA) with Bonferroni post hoc comparisons adjusted for age, BMI, and gynecological age were used to compare BMD of athletes in combined mechanical loading and menstrual status groups. We found significantly greater total hip (p=0.04) and trochanter (p=0.02) BMD (g cm−2) among eumenorrheic high/odd impact compared to eumenorrheic repetitive/non-impact athletes, and greater spine (p=0.01) and trochanter (p=0.04) BMD among high/odd impact eumenorrheic athletes compared to repetitive/non-impact oligo/amenorrheic athletes. Chi-squared analysis of BMD Z-scores adjusted for gynecological age showed a significantly greater percentage of repetitive/non-impact athletes (33.9%) compared to high/odd impact athletes (11.8%) with low spine BMD for their age (BMD Z-score ≤−1 SD) (p=0.001), indicating that a high percentage of female high school athletes participating in repetitive loading sports, and especially those with oligo/amenorrhea, may not be accruing bone at the expected rate. Female adolescent athletes should be evaluated periodically and advised of the possible negative effects of oligo/amenorrhea on bone health.