Plasma volume variation with exercise: a crucial consideration for obese adolescent boys

Previous studies have demonstrated that considerable plasma volume variations (ΔPV) occur during and after exposure to different environmental and physiological conditions. Such changes have an important effect on plasma concentration of metabolite values. Currently, no study has examined ΔPV in individuals with different body weight status and used ΔPV to correct plasma solute values. The aims of this study were to assess (i) the effect of body weight status on ΔPV and (ii) the impact of these variations on lactate ([La]) and glucose ([Glu]) concentrations in normal-weight, overweight, and obese adolescent boys. Participants performed a cycling sprint test at their maximal power output. ΔPV were calculated using 2 methods, and both lactate and glucose concentrations were compared using total circulating values (T) and corrected values (cr) for ΔPV: [La]T vs. [La]cr and [Glu]T vs. [Glu]cr. Following exercise, ΔPV values decreased significantly from rest value and were higher in obese compared with overweight and normal-weight boys (p < 0.01). Moreover, ΔPV were correlated with body weight status (r = 0.85; p < 0.05). While [La]T and [Glu]T differed among the groups, no difference persisted when these values were corrected for ΔPV. The differences between total circulating and corrected values were significant. The impact of body weight status on ΔPV and thus on various plasma measures in response to exercise is important and should be considered in further studies.