World Masters Games swimmers: BMI a help or a hindrance?

Introduction: Masters swimmers may display an age related increase to the range of pathologies present as well as physiological changes due to the aging process. There are possibilities of reduced physical activity levels, reduced metabolism and thus altered BMI compared to younger, active populations. It was hypothesized that due to a rigorous physical activity at older ages, the BMI of the swimmers at the Sydney WMG was such that a lower percentage would be classified as obese (BMI ≥ 30 kg/m2) than an appropriate comparative general population. This was despite the propensity for an increase in muscle mass from adherence to sport and the possibility of buoyancy advantages in swimming from a greater fat mass.

Methods: An online survey was utilized to investigate participants’ demographics. Electronic invitations were sent to masters games athletes who provided a valid email address.

Results and discussion: From this sub-sample (n = 527), 262 (49.7%) of the participants were male, whilst 265 (50.3%) were female. The ages ranged from 25 to 91 years (mean = 54.27). Obesity based on BMI was a health risk factor for 9.1% of the total sub-sample. Given the majority represented Australia (69% of the 527 athletes), it was deemed that the Australian general population would be the most appropriate to compare to in terms of obesity incidence. There was significantly (χ2 = 44.9, p < 0.001) lower BMI than ABS values. Comparison to samples from the other most represented countries, Canada, U.K., New Zealand and U.S.A. also showed significantly less (all p < 0.001) obesity than the national populations. The same trends were evident in gender based comparisons with the ABS data (p < 0.001). Results indicated significantly improved values of one health risk factor for these masters athletes compared to adult (age > 18 years) Australians. Given that incidence of obesity increased in the ABS sample with age and the highest proportions of obese individuals in the general Australian population were within our sample age range, the observed differences between the general Australian population and our sample could in fact be statistically even larger than revealed in this study.

Conclusion: For masters swimming at the Sydney WMG, it is shown that a key index of health, namely obesity as a health risk factor, is far lower in incidence than appropriate international populations, including the Australian population aged 18 years and over.