Kazumi Asakawa1, Katsuhiro Koyama2, Zentaro Yamagata31Department of Fundamental and Clinical Nursing, 2Department of Health and Physical Education, 3Department of Health Science, University of Yamanashi, Chuo, Yamanashi, JapanBackground: The objective of this study was to determine whether or not educational intervention using the Internet, to prevent osteoporosis, is able to increase bone strength in young women.Methods: Subjects were 253 healthy female university and junior college students aged 18–25 years. After initial measurements of bone stiffness index, a bone formation marker, and a bone absorption marker, the minimization method was used to allocate the subjects to an intervention group (n = 126) or a control group (n = 127) according to whether the measurements were above or below average. Subjects in the intervention group were instructed to perform osteoporosis prevention activities, ie, jump on the spot as high as possible ten times per day and increase calcium intake by 300 mg per day to a total of 800 mg or more per day on average. In addition, they were instructed to report the implementation status of the recommended measures via email. The researcher sent out information on osteoporosis and preventive behaviors to the subjects five times via email.Results: A total of 182 subjects, comprising 87 (69.0%) in the intervention group and 95 (74.8%) in the control group, underwent remeasurement 6 months later. Of the subjects in the intervention group, 54 (42.9%) reported their daily additional calcium intake amount and number of jumps via email. The mean amount of additional calcium taken was 216.3 ± 85.9 mg per day, and mean number of jumps performed was 6.4 ± 4.2 per day. Subjects in the intervention group were further divided into an implementation group (n = 54), consisting of subjects who sent in reports and a nonimplementation group (n = 72) who did not. No significant difference was found among the groups for rate of change in bone stiffness index and speed of sound, but there was a significant difference for broadband ultrasound attenuation (BUA) (P = 0.017). Sheffe's multiple comparison test was performed using baseline body weight and BUA values as covariates, and revealed that the rate of decrease in bone strength in the control group was larger than that in the implementation group (P = 0.049).Conclusion: Health education for preventing osteoporosis via Internet email was performed over 6 months for women aged 18 to 25 and a comparison was performed between the intervention group and control group. The intervention consisted of high jumps on the spot (ten times a day), which reduced the drop in BUA, and thus indicates robustness of the trabecular structure. This suggests that a longer intervention period may maintain or improve bone strength.Keywords: prevention, osteoporosis, Internet, ultrasound, Japanese, women