Does Long Term Swimming Participation Lead to Reduced BMD K Greenway1, P Rich1, R Villani1, P Ebling2 1Departmen of Human Biology & Movement Science, RMIT University, Melbourne, Australia. 2Department of Endocrinology, Royal Melbourne Hospital, Australia. SUMMARY. This is a preliminary study to report the relationship between bone mineral density and long term recreational swimming. The results reveal that in these subjects swimming has not compromised their skeletons. Abstract. Swimming is a particularly popular activity in Australian society with large numbers of women engaged in regular training and competition. However the weight supporting medium provided by water reduces the mechanical loading of the skeleton perhaps leading to bone loss. The purpose of the present study was to examine this possibility by measuring total and regional bone mass in pre-menopausal swimmers, compare the data with swimming history and Australian norms. Twenty seven swimmers recruited from AUSSI Masters Swimming Inc., (mean age 42years) provided data for this report. Menstrual, and swimming history were determined by interview and questionnaire. Total, Spine (L2-L4), Femoral Neck (left) and Forearm (left ultradistal) bone density were determined by DEXA(Lunar DPX-IQ). All participants had regular menses and normal onset. Lifetime annual swimming hours averaged 72 (SD 61) while annual hour swum prior to the age of 20 averaged 100(SD 80). T and Z scores for bone mass measurements (Australian reference data base) were 1.3, 1.3; 0.8, 0.9; 0.4, 0.7; -0.2, -0.2 for Total Body, AP Spine, Femoral Neck and Forearm respectively. Z scores for Total Body and Forearm correlated negatively with Lifetime Swimming (r = -0.19, -0.23 respectively) as did Total Body, AP Spine and Femur with Swimming prior to 20 years (r = -0.26, -0.18, -0.27 respectively). However none reach significance (p>0.05). On the basis of this preliminary data, we conclude that swimming has not compromised the skeletons of these women though there is evidence for a negative effect on the forearm. Furthermore, the negative relationship detected, warrant further study in a larger cohort. Introduction Is swimming a form of exercise that provides any benefit for the skeletal system in terms of bone mass? This investigation is a preliminary report subsequent to a larger prospective intervention study into the effects of impact exercise in Adult Female Swimmers. In the present study we examine the possibility of long term swimming leading to a reduction in bone mineral density. Figure 3: Correlation between BMD measured by Z scores and (a) Annual Swimming Hours prior to age 20 years and (b) Lifetime Swimming Hours for Total Body, Lumbar Spine (L2-L4), Femoral Neck and Ultradistal Radius Methods Results and Discussion The group studied was drawn from the members of a Senior Swimmers programme (AUSSI Masters Swimming Victoria) allowing the simultaneous assessment of the affect of swimming on bone mass. Lifetime annual swimming hours averaged 70 (SD 63) while annual hours swum prior to age 20 averaged 99 (SD 81) . T scores for bone mass measurements (Australia Reference Database) were 1.3 for Total Body, 0.79 for Spine, 0.4 for Femoral Neck and -0.28 for Ultradistal Radius. Z scores were 1.2 for Total Body, 0.85 for Spine, 0.6 for Femoral Neck and -0.25 for Ultradistal Radius. Z scores for Total Body and Forearm correlated negatively with lifetime swimming hours (r = -0.27 and -0.32 respectively Total Body, Spine and Femoral Neck correlated negatively with Annual Swimming Hours prior to age 20. However none reached significance (p > 0.05). On the basis of this preliminary data, we conclude that swimming has not compromised the skeletons of these women. Table 1: Subject characteristics. mean ±SD Body mass (kg) Height (cm) Age Lifetime Swimming hours* Swimming hours Prior to 20 Years age # 68 161 42 70 100 ± 10.8 ± 1.0 ± 8.9 ± 63 ± 68 * Hours of swimming per year over lifetime # Hours of swimming per year for years prior to age 20 Conclusion Swimming has not compromised the skeletons of these adult female recreational swimmers. However there is evidence for a negative effect on the forearm. Furthermore, the negative relationships detected, warrant further study in a larger cohort. Consideration needs also to be taken in regard to other activities these swimmers may have been involved in especially prior to 20 years of age. Figure 1: Bone Mass Measurements. References CASSELL, C., BENEDICT, M., and SPECKER, B. Bone mineral density in elite 7 to 9 year-old female gymnasts and swimmers. Med. Sci. Sports Exercise 28:1243-1246,1996 FORWOOD, M R. and BURR, DB. Physical activity and bone mass: exercises in futility? Bone and Mineral 21:89-112, 1993 Figure 2 Scatter plots and Trendlines for Z scores (BMD) of Total Body, Lumbar Spine, Neck of Femur and Forearm with Annual Swimming Hours prior to the age of 20 years.