Does Aquatic Exercise Build Bone Mineral Density (BMD)? Anonymous University of New Mexico Exercise Science June, 2006

BACKGROUND Special needs populations Those undertaking high impact activity have ~10% greater BMD than sedentary individuals (Torstveit and Sundgot-Borgen, 2005). Cross-sectional studies of swimmers have shown a greater BMD in vetebral BMD than sedentary individuals (Ross and Denegar, 2001).

Background There have been no head-to-head studies showing benefits of weight-bearing exercise over non-weight bearing (Briley, 2004). Non-weight bearing exercise may improve some bone mechanical properties (muscle contraction, systemic activation, bone composition) (Huang, Lin, Chang, Hsieh, Liu and Yang, 2003).

BACKGROUND FACT: Weight bearing exercise increases BMD. CONSTRUCT ? ? ? : Aquatic exercise does not increase BMD.

Purpose The purpose of this study is to determine whether or not aquatic exercise increases bone mineral density.

Rationale If aquatic exercise does help to increase bone mineral density then a large population of individuals who cannot perform weight bearing activity can have an added benefit from participating in aquatic exercise.

Hypothesis There is no difference in bone mineral density in individuals who participate in aquatic exercise versus sedentary individuals.

Methods This will be a match assignment experimental study. 60 sedentary subjects will be recruited Subjects will be match assigned into two groups: - A group of aquatic exercisers (N= 30) ages A control group of sedentary individuals (N=30) ages Subjects will be men and women (pre-menopause and taking oral contraceptives) Subjects in both groups will not be allowed to participate in any other forms of exercise during this study.

Methods BMD will be measured by dual-energy X-ray absorptiometry (DEXA) in four regions: lumbar spine, forearm, hip and femur. The study be 16 weeks in duration with BMD measurements taken at weeks 0, 4, 8, 12 and 16.

Methods The exercise group will participate in a combination of deep and shallow water aerobics for 60 minutes, 3X a week. The sedentary group will not perform any exercise for the 16 week period.

Variables Dependent Variable: Bone Mineral Density Independent Variables: IV 1: Aquatic Exercise (Yes, No) IV 2: Site of measurement IV 3: Time (Pre, Post)

Statistics Descriptive statistics on all variables 3-way ANOVA mixed design (Group x Site x Time)

Power Sample size n= 30, for each group, was determined from a power analysis using standard deviations from past research (Torstveit) and a power level of Effect size (d=.75)

Limitations Ethnicity Medical history Diet Athletic history Anthropometric Data

Anticipated Findings The aquatic exercise group will have an increase of bone mineral density over the 16 week period. BMD increase will be in the range of 3-6%. Increases are expected to be greater in the femur and hip and less in the lumbar spine and forearm. The control group will maintain or lose bone mineral density over the 16 week period.

Main References Ay, A., Yurtkuran, M. Evaluation of Hormonal Response and Ultrasonic Changes in the Heel Bone by Aquatic Exercise in Sedentary Postmenopausal Women. American Journal of Physical Medicine and Rehabilitation, Dec. 2003, v.18(12), p Briley, John. Bone Health: A Weight-Bearing Argument. Washington Post, Tuesday, July 27, 2004; p. HE03. Huang, T.H., Lin, S.C., Chang, F.L., Hsieh, S.S., Liu, S.H., and Yang, R.S. Effects of Different Exercise Modes on Mineralization, Structure, and Biomechanical Properties of Growing Bone. Journal of Applied Physiology, July, 2003; p. Ross, M., Denegar, C. Effect of Exercise on Bone Mineral Density in Postmenopausal Women. Strength and Conditioning Journal, 2001; v. 23(4), p Torstveit, M.K., and Sundgot-Borgen, J. Low Bone Mineral Density is Two to Three Times More Prevalent in Non-Athletic Premenopausal Women Than in Elite Athletes: A Comprehensive Controlled Study. British Journal of Sports Medicine, 2005; v.39, p