Differential Cytokine Response To Exercise And Environmental Conditions Dependent On Application Of Plasma Volume Corrections

Correcting for plasma volume (PV) is common practice, however, is not used consistently. PURPOSE: To examine the response of tumor necrosis factor alpha (TNFα), interleukin 6 (IL6) and 10 (IL10) to cycling in various environmental conditions both when corrected and not corrected for PV shifts. METHODS: Seven men (25 ± 3 yrs; 80.8 ± 6.2 kg; 182.5 ± 6.0 cm) volunteered to participate in this within subjects designed study. Participants completed six trials separated by at least 72 hours. During visit one, participants provided informed written consent before completing a maximal graded exercise test on a cycle ergometer. The remaining visits were counterbalanced and consisted of 5 °C (LT), 23 °C/45%RH (MT/MH), 23 °C/70%RH (MT/HH), 35 °C/20%RH (HTLH) and 35 °C/45%RH (HTMH). Each session consisted of 60 minutes of cycling at 60%VO2max followed by 15 minutes of recovery, a time to exhaustion at 90%VO2max and 60 minutes of passive recovery. Blood samples were obtained prior to exercise, after 60 minutes of cycling, after the time to exhaustion, and after recovery. Blood samples were analyzed by ELISA for circulating concentrations of TNFα, IL6 and IL10 as well as hematocrit and hemoglobin via an automated hematology analyzer. Resulting data were both corrected and not corrected for changes in PV before calculating the area under the curve with respect to increase using the standard trapezoidal method. Data were analyzed via 2 x 5 (correction vs trial) repeated measures ANOVA. RESULTS: An interaction (F = 3.72; p = 0.017) was observed for TNFα, which was different between corrections for all trials (p ≤ 0.001). When no PV correction was applied, both HTLH and HTMH resulted in a greater TNFα response to exercise (p < 0.05), while no differences were observed between the LT, MTMH or MTHH conditions. When data were PV corrected, significant differences were observed between LT and all conditions (p < 0.05) except MTHH (p = 0.481). The only other difference occurred between MTMH and HTMH (p = 0.039). No interactions were observed for IL6 (F = 3.83; p = 0.081) or IL10 (F = 1.91; p = 0.149), though both resulted in significant main effects for correction and trial (p < 0.05). CONCLUSION: These data demonstrate the use of PV corrections can have significant effects on data, highlighting the need for consistency in approach within the scientific literature.