OBJECTIVESThe purpose of this study was to examine the relation between exercise intensity and immune function.

METHODSTen healthy young males underwent a constant work rate exercise of three levels, 90%, 80% and 70% ventilatory threshold (VT) work rate, for 20 min on a bicycle ergometer. These work rates were calculated for each individual based on his VT work rate obtained by the incremental exercise tests. Blood samples were collected before and after the exercise, and immune function indices were measured.

RESULTSCompared with the obtained[Formula: see text] at[Formula: see text] in the incremental test, the[Formula: see text] with the exercise of 70% VT work rate was at a similar level and the one with the exercise of 90% or 80% VT work rate had a significantly greater value. The numbers of leukocytes and neutrophils significantly increased in the 90% and 70% VT work rate groups. In 80% VT work rate group, the CD4/CD8 ratio was significantly depressed. The CD16(+)CD57(-) (%), natural killer cell populations, had a tendency to increase at 80% VT work rate, and also the CD16(+)CD57(-) (%) had a similar tendency at 90% or 80% VT work rate.

CONCLUSIONSThis study shows that moderate exercise reaching or exceeding the VT level acutely affects T cell and NK cell subsets.