Depression of plasma glutamine concentration after exercise stress and its possible influence on the immune system

Objective: To determine whether plasma glutamine levels can be used as an indicator of exercise-induced stress, and to consider the possible effects of low plasma glutamine concentrations on the immune system.Methods: We used two exercise regimens: in Trial 1 seven male subjects were randomly stressed on a treadmill at 0, 30%, 60%, 90% and 120% of their maximal oxygen uptake (VO(2)max); in Trial 2 five highly trained male subjects underwent intensive interval training sessions twice daily for ten days, followed by a six-day recovery period.Results: Plasma glutamine concentrations decreased significantly from an average of 1244+/- 121 mu mol/L to 702 +/- 101 mu mol/L after acute exercise at 90% VO(2)max (P <0.05) and to 560 +/- 79 mu mol/L at 120% VO(2)max (P <0.001). Four of the five subjects showed reduced plasma glutamine concentrations by Day 6 of the overload training trial, with all subjects displaying significantly lower glutamine levels by Day 11. However, glutamine levels showed a variable rate of recovery over the six-day recovery period, with two subjects' levels remaining low by Day 16.Conclusions: Reduced plasma glutamine concentrations may provide a good indication of severe exercise stress.