title: Self-reported recreational exercise combining regularity and impact is necessary to maximize bone mineral density in young adult women: a population-based study of 1,061 women 25 years of age.
abstract: Recreational physical activity in 25-year-old women in Sweden increases bone mineral density (BMD) in the trochanter by 5.5% when combining regularity and impact. Jogging and spinning were especially beneficial for hip BMD (6.4-8.5%). Women who enjoyed physical education in school maintained their higher activity level at age 25.
  
  
  BACKGROUND
  The aims of this study were to evaluate the effects of recreational exercise on BMD and describe how exercise patterns change with time in a normal population of young adult women.
  
  
  METHODS
  In a population-based study of 1,061 women, age 25 (±0.2), BMD was measured at total body (TB-BMD), femoral neck (FN-BMD), trochanter (TR-BMD), and spine (LS-BMD). Self-reported physical activity status was assessed by questionnaire. Regularity of exercise was expressed as recreational activity level (RAL) and impact load as peak strain score (PSS). A permutation (COMB-RP) was used to evaluate combined endurance and impacts on bone mass.
  
  
  RESULTS
  More than half of the women reported exercising on a regular basis and the most common activities were running, strength training, aerobics, and spinning. Seventy percent participated in at least one activity during the year. Women with high RAL or PSS had higher BMD in the hip (2.6-3.5%) and spine (1.5-2.1%), with the greatest differences resulting from PSS (p < 0.001-0.02). Combined regularity and impact (high-COMB-RP) conferred the greatest gains in BMD (FN 4.7%, TR 5.5%, LS 3.1%; p < 0.001) despite concomitant lower body weight. Jogging and spinning were particularly beneficial for hip BMD (+6.4-8.5%). Women with high-COMB-RP scores enjoyed physical education in school more and maintained higher activity levels throughout compared to those with low scores.
  
  
  CONCLUSIONS
  Self-reported recreational levels of physical activity positively influence BMD in young adult women but to maximize BMD gains, regular, high-impact exercise is required. Enjoyment of exercise contributes to regularity of exercising which has short- and long-term implications for bone health.
authors.affiliation: Department of Orthopaedics, Lund University, Skåne University Hospital, 205 02 Malmö, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Callréus
authors.forename: F
authors.initials: F
authors.lastname: McGuigan
authors.forename: K
authors.initials: K
authors.lastname: Ringsberg
authors.forename: K
authors.initials: K
authors.lastname: Akesson
mesh_terms: D000328:Adult; D000886:Anthropometry / Q000379:methods; D015519:Bone Density / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005260:Female; D005269:Femur / Q000502:physiology; D005272:Femur Neck / Q000502:physiology; D006801:Humans; D008159:Lumbar Vertebrae / Q000502:physiology; D009043:Motor Activity / Q000502:physiology; D010806:Physical Education and Training / Q000706:statistics & numerical data; D011998:Recreation / Q000502:physiology; D012621:Seasons