Effects of rope-jump training on the os calcis stiffness index of postpubescent girls

Purpose: The specific aims of the study were to 1) determine what effects dose-dependent rope jumping had on os calcis stiffness index (OCSI) and 2) determine whether OCSI values measured by quantitative ultrasound (QUS) were dependent or independent of the values of bone mineral content (BMC) determined by dual energy x-ray absorptiometry (DXA) at the lumbar spine and proximal femur (femoral neck; greater trochanter). Methods: Upon study entry, girls were randomly assigned to either one of two treatment groups (high volume; low volume) or a control group. Thirty-seven high school girls were recruited to participate in the study. QUS and DXA measurements were made at baseline and at 4-month follow-up. Students in the high-volume and low-volume groups jumped rope for 10 and 5 min, respectively. Results: The follow-up mean OCSI values for the high-volume, low-volume, and control conditions were 103.95 +/- 12.55, 102.09 +/- 12.70, and 99.05 +/- 9.84, respectively. A statistically significant difference (P = 0.033) was identified between the high-volume and control groups. Baseline and follow-up OCSI values were significantly correlated with baseline and follow-up BMC measures of the femoral neck (r = 0.60, r = 0.59), greater trochanter (r = 0.47, r = 0.40), and lumbar spine (r = 0.56, r = 0.56). Conclusions: High-volume rope jumping increases the OCSI more than the control condition in postpubescent girls. Furthermore, the OCSI measured by QUS is moderately related to proximal femur and lumbar spine BMC measured by DXA.