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Strenuous exercise is associated with a transient decline in circulating lymphocytes, possibly through increased apoptosis. Intestinal lymphocytes are important effector cells of intestinal immune function but have not been studied in relation to exercise.

Aim:  The purpose of the present study was to examine the effect of exercise on intestinal lymphocyte phenotypes and apoptosis.

Methods:  Female C57BL/6 mice (n = 112) were randomized to: (1) treadmill running (90 min, 32 m min⁻¹, 8° grade) and killed immediately after exercise, (2) treadmill running and killed 2 h after exercise, (3) treadmill running and killed 24 h after exercise or (4) a non‐exercised control condition with exposure to treadmill noise and vibration without running.

Results:  Flow cytometry indicated that the total intestinal CD3⁺T (P < 0.01), CD4⁺T (P < 0.005), CD8⁺T (P < 0.05), pan‐NK (P < 0.005) and CD19⁺B (P < 0.05 …