Plasma interleukin-6 during strenuous exercise: role of epinephrine.
Level 3 - non-randomized controlled study
Non-randomized crossover comparative study with a fixed sequence
PubMed 11502577 · doi:10.1152/ajpcell.2001.281.3.C1001
What was done
Seven healthy men completed a 2.5-hour treadmill run at 75% of maximal oxygen consumption. One month later, the same participants received a 2.5-hour epinephrine infusion designed to match the plasma epinephrine levels achieved during the running trial. Plasma concentrations of interleukin-6 (IL-6), lymphocytes, and neutrophils were measured during and after both interventions.
What was found
Plasma IL-6 increased 29-fold during exercise, peaking at the end of the bout, compared to a 6-fold increase during epinephrine infusion, which peaked 1 hour post-infusion. Lymphocyte counts rose to equivalent levels during both trials, though post-exercise lymphocyte decline was greater than post-infusion decline. Neutrophil concentrations increased threefold following exercise but showed no change during or after epinephrine infusion.
Why it matters
This demonstrates that systemic epinephrine elevation accounts for only a minor fraction of the massive IL-6 release and none of the neutrophilia triggered by prolonged strenuous exercise.
Limits
The sample was very small (n = 7) and restricted to healthy men. The study used a fixed trial order (exercise followed by infusion one month later) without randomization. Absolute concentration values and statistical variance metrics were not reported in the abstract.
Cited by
- contradicts IL-6 is secreted by muscles after exercise rather than during the bout of exercise itself.