Body water indices as markers of aging in male masters swimmers.

The association of age and weekly swim training distance with body water, lean tissue, fat mass and regional adiposity was examined in 27 male masters swimmers. Subjects ranged in age from 25.3 to 73.1 years (mean age = 47.7 ± 11.1 years). Weekly swim distances, estimated from self-reported swim logs, were from 3 400 to 17 500 m and averaged 10 016 ± 4 223 m. Total body water (TBW), and extracellular water (ECW) were predicted from multi-frequency bioelectrical impedance analysis and intracellular water was estimated by difference. Lean soft tissue, bone mineral content, fat mass, and percent body fat were estimated from dual-energy X-ray absorptiometry. Measures of skinfold thickness, waist circumference, and abdominal sagittal diameter provided an indication of regional adiposity. Total body water, ECW, and ICW mean values (ranges) were as follows: 47.4 ± 4.6 L (37.9-56.9 L), 19.6 ± 1.8 L., (16.4-24.8 L), and 27.8 ± 3.2 L (21.5-34.4 L). Mean percent body fat levels were 21.9 ± 6.6% and ranged from 10.3 to 34.9%. Age was negatively associated with ICW (p = 0.02) and with the ICW/TBW ratio (p = 0.00). Multiple-linear regression analysis backward method suggested that both lean tissue and fat mass were predictors of ICW although the association with fat mass did not reach statistical significance (p = 0.00 and p = 0.06 for lean and fat mass respectively). There was a tendency for greater lower abdominal thickness with increasing age (p = 0.08), but no other associations were observed between age or with swimming and body composition variables. Changes in ICW and the ration of ICW to TBW appeared to be the strongest marker of aging in this group of adult male competitive swimmers. Key PointsSubject age was negatively associated with the volume of intracellular water and with the intracellular-to-total body water ratio.There was a trend for age to be positively related to lower abdominal thickness.Weekly swim training distance was not associated with body water, lean tissue, fat mass or regional adiposity.Lean tissue mass appeared to be a strong positive predictor of total body water and the intra- and extracellular fractions.There was a trend for fat mass to be a negative predictor of intracellular water volume.