title: 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.
abstract: OBJECTIVE
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Health Sciences, University of Jyväskylä, Jyväskylä, Finland.
authors.forename: Ari
authors.initials: A
authors.lastname: Heinonen
authors.forename: Jyri
authors.initials: J
authors.lastname: Mäntynen
authors.forename: Pekka
authors.initials: P
authors.lastname: Kannus
authors.forename: Kirsti
authors.initials: K
authors.lastname: Uusi-Rasi
authors.forename: Riku
authors.initials: R
authors.lastname: Nikander
authors.forename: Saija
authors.initials: S
authors.lastname: Kontulainen
authors.forename: Harri
authors.initials: H
authors.lastname: Sievänen
keywords: bone and bones; bone mineral density; exercise; osteoporosis; women