INFLUENCE OF EXERCISE-INDUCED PLASMA-VOLUME CHANGES ON THE INTERPRETATION OF BIOCHEMICAL DATA FOLLOWING HIGH-INTENSITY EXERCISE

Objective: To assess the effects that exercise-induced plasma volume c hanges (PVCs) have on the interpretation of biochemical and hormonal p arameters in the blood of athletes after high-intensity exercise. It w as hypothesized that two unrelated high-intensity exercise protocols, performed by two separate subject groups each using different exercise modes, would result in similar percentage changes in plasma volume (% Delta PV). It was further hypothesized that the %Delta PV, measured in both protocols, would comparably influence the interpretation of bioc hemical variables measured following exercise. Design: An experimental before-after trial on volunteers was performed. Two different exercis e modes employing two different high-intensity acute exercise protocol s were investigated. Eight male swimmers performed an interval trainin g session (ITS) consisting of 15 x 100-m freestyle efforts at 95% of t heir maximal exercise intensity, and eight male runners performed a mu ltistage discontinuous treadmill test (MSD) to volitional exhaustion. Setting: The Human Performance Laboratory at the Department of Human M ovement at the University of Western Australia. Main outcome measures: Blood samples obtained before, immediately after, and 30, 60, and 120 min during recovery were analyzed for plasma volume changes, urea, ur ic acid, creatinine, albumin, calcium, iron, transferrin, testosterone , cortisol, and sex hormone-binding globulin (SHBG). Main results: The ITS and MSD protocols produced similar and significant alterations (p < 0.01) in plasma volume. Both protocols also elicited significant fl uctuations (p < 0.01) in the concentration of most of the parameters m easured (excluding iron). When albumin, transferrin, testosterone, and SHBG values were adjusted for the significant %Delta PV, their concen trations did not change over the experimental period, suggesting that the changes in measured concentration of these parameters may be, in p art, due to changes in plasma volume. However, urea, uric acid, creati nine, calcium, and cortisol, when corrected for %Delta PVC, still demo nstrated significant changes (p < 0.01). Conclusions: It is recommende d, when sampling biochemical and hormonal parameters in blood followin g an acute bout of exercise, that corrections for PVCs should be condu cted. Apparent changes in blood solutes may reflect PVCs. PVCs should be taken into consideration when interpreting results regardless of ex ercise protocol and exercise mode performed.