No abstract

This randomized, double-blind, placebo-controlled study was designed to determine the influence of 6% carbohydrate (C) vs. placebo (P) beverage ingestion on cytokine responses (5 total samples over 9 h) to 2.5 h of high-intensity running (76.7 +/- 0.4% maximal O2 uptake) by 30 experienced marathon runners. For interleukin-6 (IL-6), a difference in the pattern of change between groups was found, highlighted by a greater increase in P vs. C immediately postrun (753 vs. 421%) and 1.5 h postrun (193 vs. 86%) [F(4,112) = 3.77, P = 0.006]. For interleukin-1-receptor antagonist (IL-1ra), a difference in the pattern of change between groups was found, highlighted by a greater increase in P vs. C 1.5 h postrun (231 vs. 72%) [F(2,50) = 6.38, P = 0.003]. No significant interaction effects were seen for bioactive IL-6 or IL-1 beta. The immediate postrun plasma glucose concentrations correlated negatively with those of plasma cortisol (r = -0.67, P < 0.001); postrun plasma cortisol (r = 0.70, P < 0.001) and IL-6 levels (r = 0.54, P = 0.003) correlated positively with levels of IL-1ra. Taken together, the data indicate that carbohydrate ingestion attenuates cytokine levels in the inflammatory cascade in response to heavy exertion.

The effect of 45 min of high- (80% VO2max) versus moderate- (50% VO2max) intensity treadmill exercise on circulating leukocyte and lymphocyte subpopulations, catecholamine and cortisol concentrations, and the mitogen-stimulated lymphocyte proliferative response was investigated in 10 well-conditioned (mean VO2max 66.0 +/- 1.9 ml/kg/min), young males (mean age 22.1 +/- 1.3 yrs). Blood samples were taken before and immediately after exercise, with three more samples taken during 3.5 h of recovery. Treatment order on the treadmill (graded walking at 7.3 +/- 0.1 km/h, 6.5 +/- 0.6% grade, versus level running at 16.1 +/- 0.3 km/h) was counterbalanced, with subjects acting as their own controls and results analyzed using a 2 x 5 repeated measures ANOVA. The concanavalin A- (Con A) stimulated lymphocyte proliferative response was decreased at 1 h and 2 h post-exercise relative to baseline levels following both exercise-intensity conditions. However, when adjusted on a per-T cell (CD3+) basis to account for the change in number of T cells in the in vivo assay, only the high-intensity exercise condition was associated with a 1-h post-exercise decrease (21%, p = 0.05) in the proliferative response relative to baseline. Exercise at 80% versus 50% VO2max resulted in significantly greater increases in cortisol and epinephrine concentrations, providing a physiological rationale for the immediate-post-exercise lymphocytosis, 1- to 3.5-h lymphocytopenia, and the decrease in Con A-stimulated lymphocyte proliferative response (per CD3+ cell) that occurred in greater measure following high-intensity exercise.

This randomized, double-blind, placebo-controlled study was designed to determine the influence of carbohydrate supplementation on the granulocyte and monocyte response to 2.5 h of high-intensity running [76.7 +/- 0.4% of maximal oxygen consumption (VO2max)]. Thirty experienced marathon runners (VO2max 53.4 +/- 1.0 mL.kg-1.min-1, age 41.5 +/- 1.4 y) were randomly assigned to carbohydrate-supplement (n = 17) and placebo (n = 13) groups. Subjects rested for 10-15 min before a blood sample was taken at 0715, and then ingested 0.75 L carbohydrate beverage or placebo. At 0730 subjects began running at 75-80% of VO2max for 2.5 h, and drank 0.25 L carbohydrate or placebo fluid every 15 min. Immediately after the 2.5-h run (1000), another blood sample was taken, followed by 1.5-h, 3-h, and 6-h recovery samples. Carbohydrate supplementation had a significant effect compared with placebo on the pattern of change in plasma glucose and cortisol, and the blood concentration of neutrophils (F[14, 112] = 5.13, P = 0.001) and monocytes (F[14, 112] = 4.78, P = 0.001), but not on blood granulocyte and monocyte phagocytosis or oxidative burst activity after 2.5 h of intensive running.