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Effect of exercise induced hypohydratation on body composition measurements in active and athletic subjects

par Klass, Malgorzata ;Rivière, Valérian;Booghs, Cédric ;Carpentier, Alain
Référence PO-CPP-30 Training & Testing 3(6th - 9th July 2016: Vienna – Austria), 21st Annual Congress of the European College of Sport Science, page (194-195)
Publication Publié, 2016-07

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Introduction Body composition is frequently assessed in active subjects and athletes to quantify its impact on performance or the effect of different kinds of physical/nutritional interventions. However subject hydration varies along the day and in between days due to physical activity which may induce errors in body composition estimation (1,2). Therefore the aim of present study is to quantify the effect of an exercise induced hypohydration on body composition measurements using different methods. Methods Thirteen active (7 males) and 13 athletic (7 males) subjects took part in the experiments. Their body composition was assessed using anthropometric methods (skinfolds), multi-frequency bioelectrical impedance analyser (M-BIA) and dual-energy X-ray absorptiometry (DXA) before and after a run on treadmill that induces a body weight decrease of 2%. Correlations between individual weight losses and body composition changes were calculated. For DXA, segmental changes and correlation between initial percentage of fat mass and body composition changes was also calculated. Results Athletic subjects presented a significantly lower initial fat mass percentage (13%) compared to active subjects (24%) [P<0.05]. Average body composition changes between pre and post exercise are expressed in percentage of pre-exercise values. The lean mass measured by DXA and M-BIA decreased post-exercise by 2.5 and 1% respectively [P<0.01]. The fat mass was reduced post-exercise when measured using DXA (2.3%) and M-BIA (8.2%) [P<0.01]. Body fat percentage estimated using M-BIA was reduced by 5% [P<0.01] and did not change for DXA. Skinfolds sum and fat percentage calculated using Durnin and Wormersley equation combined to Siri equation (DWS) were slightly reduced (1.7%) post-exercise [P<0.01]. For DXA and M-BIA, fat mass changes were correlated with weight loss [P<0.05], whereas correlation was not significant for lean mass. Body fat percentage changes were significantly correlated with weight loss for DXA but not for M-BIA and DWS. For DXA, decreases of fat mass and lean mass were located respectively in the trunk and in trunk and legs. Initial percentage of body fat mass was correlated with changes of fat and lean mass. Discussion Changes of fat mass and lean mass due to exercise induced hypohydration were predominantly located in the trunk and were dependent on the method used. It also appears that initial body composition, which differs between athletic and less active subjects, may influence errors induced by hypohydration. References 1.Rodriguez-Sanchez et al 2014, Int J Sport Nutr Exerc Metab 25:60-68. 2.Saunders et al 1998, Med Sci Sports Exerc 30, 885-92.