Effects of High-Impact Training and Detraining on Femoral Neck Structure in Premenopausal Women: A Hip Structural Analysis of an 18-Month Randomized Controlled Exercise Intervention with 3.5-Year Follow-Up

PURPOSE: This study evaluated the training effects of an 18-month exercise intervention and subsequent 3.5-year follow-up on femoral neck structure in premenopausal women. METHODS: Of 98 women who participated in this randomized controlled study, 84 (39 trainees and 45 controls) completed the 18-month intervention. At both 18 months and 3.5 years, dual-energy X-ray absorptiometry data on 22 trainees and 22 control participants (ages 35-45 y) were available for hip structural analysis. The section modulus (Z), cross-sectional area (CSA), and subperiosteal width at the femoral neck were analyzed. Lower-leg explosive power and estimated maximal oxygen uptake (Vo(2)max) were assessed by vertical countermovement jump and standardized 2 km walking test, respectively. Progressive supervised high-impact exercises were done three times per week for 18 months. RESULTS: Significant between-group differences in favour of trainees were observed after the 18-month intervention in Z (3.2%, p=0.047) and CSA (2.8%, p=0.043). At the 3.5-year follow-up point, the exercise-induced benefits in Z and CSA had diminished and were statistically insignificant. A between-group difference in favour of trainees was observed in lower-limb power after intervention (4.2%, p=0.002) and at 3.5-year follow-up (5.1%, p=0.003). A similar difference was seen in estimated Vo(2)max (5.6% after intervention, p=0.002, and 4.6% at 3.5-y follow-up, p=0.005). CONCLUSION: The 18-month high-impact exercise intervention strengthened the femoral neck in premenopausal women by enhancing its structural properties; however, this benefit was not maintained at 3.5-year follow-up. In contrast, the exercise benefits on physical performance continued to be maintained 3.5 years after intervention.