A 12-month continuous and intermittent high-impact exercise intervention and its effects on bone mineral density in early postmenopausal women: a feasibility randomized controlled trial

BACKGROUND : Intermittent mechanical loading generates greater bone adaptations than continuous mechanical loading in rodents but has never been evaluated in humans. This study aimed to evaluate the feasibility of a continuous and intermittent countermovement jump (CMJ) intervention for attenuating early postmenopausal BMD loss. METHODS: 41 healthy early postmenopausal women (age=54.6 +/- 3.4 years) were randomly assigned to a continuous countermovement jumping group, an intermittent countermovement jumping group or a control group for 12 months. Adherence and dropout rates were recorded along with bone mineral density (BMD) at lumbar spine, femoral neck and trochanter sites at baseline, 6 months and 12 months. RESULTS: 28 participants completed the study. Dropout rate during the intervention (from the initiation of exercise) was 36% from continuous and 38% from intermittent countermovement jumping groups. For the participants that completed the intervention, adherence was 60.0 +/- 46.8% for continuous and 68.5 +/- 32.3% for intermittent countermovement jumping. The control group lost significant lumbar spine BMD (% difference=-2.7 [95%CI: -3.9 to -1.4]) and femoral neck BMD (% difference=-3.0% [95%CI: -5.1 to -0.8]). There was no statistically significant change in BMD for either countermovement jumping group. There was no statistically significant difference in BMD change between continuous or intermittent countermovement jumping groups when compared with the control group. CONCLUSIONS: Adherence and dropout rates were in line with previous similar interventions. To evaluate the effect of continuous and intermittent exercise on BMD, future studies should focus on maintaining participant engagement and adherence to the exercise intervention.