The Effect of Mechanical Loading on Bone Material Strength and Microarchitecture in Postmenopausal Women
Condition: Osteoporosis; Postmenopause
MeSH terms: Osteoporosis
Study type: Interventional

Summary: 
      Osteoporosis is a large public health disease, characterized by low bone mass and micro
      architectural deterioration of bone tissue, resulting in enhanced bone fragility and
      consequent increase in fracture risk. Osteoporosis is present when bone mineral density (BMD)
      or content (BMC), measured by dual-energy X-ray absorptiometry (DXA), is more than 2.5 SDs
      below the mean value of the young adult. BMD measured by DXA is a surrogate measure of bone
      strength and is the primary determinant of fracture risk in both men and women. However, the
      majority of fragility fractures occur in women and in individuals who do not have
      osteoporosis according to these standards, indicating that BMD is just one among several
      indicators of bone health and that assessment of fracture risk should also rely on other bone
      properties. Newer imaging methods, such as quantitative computerized tomography (QCT), can
      complement information from DXA-measurements due to its ability to assess volumetric BMD and
      bone geometry and to differentiate between cortical and trabecular bone compartments. Bones
      are composite materials made predominantly of living cells, extracellular matrix, water and
      lipids. This composite nature of the bone material enables it to absorb stresses by elastic
      deformation and to endure high loads before fracturing. A new in vivo measurements of bone
      material strength can be used to evaluate bone mechanical properties and thereby the fracture
      risk. It is well established that the skeleton benefits, in terms of increased density, from
      regular physical activity. However, changes in BMD are still the main surrogate for assessing
      improvements in exercise-induced bone health despite the experimental findings as well as
      findings in humans showing that improvements in mechanical bone properties are independent of
      changes in BMD. These improvements in mechanical bone properties may be due to changes in
      bone shape or matrix composition. It could then be argued that a decrease in BMD is only one
      of the possible manifestations of osteoporosis and that bone strength or fragility is
      multifactorial. The objective for this study is to investigate the role of mechanical loading
      on bone material strength and bone microarchitecture in middle-aged women. The overall
      hypothesis is that mechanical loading is a regulator of bone material strength and
      microarchitecture in middle-aged women. This is an intervention study where the participants
      will act as their own controls. The investigators intend to include 40 postmenopausal and
      healthy women 50-60 years of age in the study. Advertisements in local papers and at the
      hospital will be used to come into contact with suitable study subjects. The women will be
      asked to perform an intervention program, including jumping on one leg every day during a
      3-month period according to a protocol with a gradually increasing load/number of jumps. The
      women have to choose one of their legs as intervention-leg and stick to the chosen leg
      throughout the study. The leg without intervention will be used as a control. Both bone
      material strength (BMS) and bone microarchitecture will be measured before and after
      intervention in both legs (tibia). The operators measuring BMS (OsteoProbe®) and bone
      microarchitecture (high resolution pQCT) will be blinded concerning each participant's choice
      of leg for intervention. In addition, subjects will be asked to register daily physical
      activity in a structured diary. The primary outcome measure will be changes in bone material
      strength (BMS) in the lower leg (tibia) with intervention compared to the leg (tibia) without
      intervention. Participants will attend two clinic visits, at baseline and after 3 months when
      the intervention period is completed. The secondary outcome measures will be changes in total
      volumetric density, cortical volumetric density, cortical cross sectional area and trabecular
      bone volume fraction in the lower leg (tibia) with intervention compared to the leg (tibia)
      without intervention.
    


Intervention name(s): Jumping on one leg
Intervention type(s): Behavioral
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: Basic Science