Self-selected recreational exercise has no impact on early postpartum lactation-induced bone loss. Med. Sci. Sports Exerc., Vol. 30, No. 6, pp. 831-836, 1998. Although exercise is known to positively impact bone mineral density (BMD), its effect on lactation-induced BMD loss has not been previously evaluated in a case-control study.
Purpose: The purpose of this study was to compare lactation-induced bone changes in women who engaged in regular, self-selected, recreational exercise versus those who refrained from such during early postpartum.
Methods: Subjects were 20 healthy, lactating women who either exercised regularly (exercise, E; N = 11) or refrained from such (control, C; N = 9) during the first 3 months postpartum. Although preconception V˙O2max was significantly higher in E than C (E = 54.1, C = 36.9 mL·min−1·kg−1), no significant group differences were observed for parity, age, height, weight (WT), % body fat, dietary calcium intake, lactation calcium loss, and serum estradiol. Total body (TB), lumbar spine (LS), and femur neck (FN) BMD were measured within 2 wk of parturition and repeated at 3 months postpartum by dual energy x-ray absorptiometry.
Results: Although TB was unchanged, BMD decreased significantly from baseline in both groups at LS (C = −5.4, E= −4.1%) and FN (C = −2.7, E = −2.8%). WT decreased significantly over time but was not significantly correlated with BMD loss. No significant group by time interactions were observed for WT or BMD changes.
Conclusion: These results suggest that regular, self-selected, recreational E has no impact on early postpartum lactation-induced BMD loss.
Department of Obstetrics and Gynecology, MetroHealth Medical Center, Cleveland, OH 44109
Submitted for publication April 1996.
Accepted for publication September 1997.
Dr. Tom Oakley and the Outpatient Radiology Department staff at MetroHealth Medical Center generously donated all the Hologic bone scans and analyses. We thank Susan Ridzon, M.A., R.D. for assistance with nutritional analyses and data management. This project was supported by National Institutes of Health Grant HD-RO1-21268 and the General Clinical Research Center and the Department of Obstetrics and Gynecology at MetroHealth Medical Center.
Address for correspondence: Kathleen D. Little, Ph.D., Department of Human Performance and Exercise Science, Youngstown State University, Youngstown, OH 44555. E-mail: firstname.lastname@example.org.