Amenorrhea in Exercising Women Results in Adaptations in vBMD, Bone Geometry, and Estimated Bone Strength
Open Access
- Author:
- Southmayd, Emily Anne
- Area of Honors:
- Kinesiology
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Dr. Mary Jane De Souza, Thesis Supervisor
Jinger S. Gottschall, Thesis Honors Advisor - Keywords:
- Amenorrhea
Exercise
BMD
Bone
vBMD
geometry
strength - Abstract:
- Exercise is known to be an osteogenic stimulus, improving bone mineral density (BMD) and reducing the long-term risk of fracture. However, through metabolic and hormonal mechanisms, exercising women with menstrual cycle disturbances could be at risk for decreased BMD and negative adaptations in bone geometry that compromise bone strength secondary to insufficient caloric intake to compensate for energy expenditure. The purpose of this study was to compare volumetric BMD (vBMD), bone geometry, and estimated bone strength (bone strength index (BSI) and strength strain index (SSI)) between eumenorrheic (EU, n=9) versus amenorrheic (AM, n=18) exercising women. Bone variables were assessed at the tibia and radius using peripheral quantitative computed tomography. EU and AM women were similar in age (p>0.05) (20.7±0.5yrs), weight (57.2±1.5kg), BMI (20.6±0.4kg/m2), and body composition. Volumetric BMD, bone geometry, and estimated bone strength at the distal and proximal tibia and at the distal radius were not different (p>0.05) between EU and AM women. At the proximal radius, total vBMD, cortical vBMD, cortical thickness, endosteal circumference, muscle area, and the ratio of bone area to muscle area were also statistically similar (p>0.05) between the groups. However, EU women demonstrated a larger total area (p=0.045), cortical area (p=0.064), periosteal circumference (p=0.045), and SSI (p=0.057) at the proximal radius compared with AM women. These findings were no longer significant after controlling for lean body mass. The results suggest that the alteration in reproductive hormones that typically results from an energy deficiency may negatively impact bone geometry and, consequently, bone strength. Because these findings were observed only at the radius, it may be that the osteogenic effect of exercise on the weight-bearing limbs is protective against the skeletal consequences of an energy deficiency in young, exercising women. However, this study may be underpowered and require a larger sample size to adequately address the research question.