Does weight-bearing exercise protect against the effects of exercise-induced oligomenorrhea on bone density?
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Does weight-bearing exercise offset bone loss associated with oligomenorrhea? If so, bone mineral density (BMD) will be stable at weight bearing sites but decrease at non-weight-bearing sites with increasing duration of oligomenorrhea. To test this hypothesis, BMD (g/cm2), was measured by dual-energy X-ray absorptiometry in 41 oligomenorrheic ballet dancers aged 17.7±0.2 years (mean ± SEM) and 46 age-matched controls with normal menstrual function. BMD correlated negatively with the duration of oligomenorrhea at weight-bearing and non-weight-bearing sites (femoral neck,r=−0.33,p<0.05; Ward's triangle,r=−0.29,p=0.06; trochanter, r=−0.33,p<0.05; lumbar spine,r=−0.25,p=0.1; skull,r=−0.29,p=0.06; arms,r=−0.32,p<0.05; ribs,r=−0.30,p=0.06). The slopes of the regression of BMD on duration of oligomenorrhea were greater at the proximal femur (trochanter, −0.28±0.13, femoral neck, −0.24±0.11; Ward's triangle, −0.29±0.15) than the skull (−0.15±0.08,p<0.05,p<0.1,p<0.1 respectively). The slopes at the trochanter and femoral neck were also greater than at the ribs (−0.10±0.05; bothp<0.1). In the dancers with oligomenorrhea of less than 40 months duration, BMD was higher than the age-predicted mean at weight-bearing sites (except the lumbar spine), but not at non-weight-bearing sites (femoral neck, 9.1±3.4%; Ward's triangle, 10.0±1.7%; trochanter, 9.4±4.1%, allp<0.05; lumbar spine , −2.1±2.7%, NS; skull, −2.5±2.1%, NS; ribs, −3.0±1.6% NS; arms, −3.9±1.6%;p<0.05). In the dancers with greater than 40 months oligomenorrhea, BMD was no higher than the age predicted mean, at the weight bearing sites, and was lower at non-weight bearing sites (femoral neck, 4.3±2.3%, NS; Ward's triangle, 3.5±3.2%, NS; trochanter, 2.1±2.7%, NS; lumbar spine, −3.8±2.1%, NS; arms, −7.5±0.8%,p<0.05; skull, −6.2±1.8%,p<0.01; ribs, −5.4±1.1%,p<0.0001). In conclusion, weight-bearing exercise is unlikely to offset the deleterious effects of oligomenorrhea. Bone loss appears to occur at all sites but may begin from a higher level at weight-bearing sites and may proceed more rapidly.
KeywordsBallet dancers Bone mineral density Oligomenorrhea
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