Immune Response to a 30-Minute Walk

PURPOSE: To measure several components of immune changes related to walking 30 min with or without an exercise assist device compared with sitting. METHODS: Fifteen healthy and nonobese female subjects (37.5 +/- 3.1 yr of age) accustomed to regular walking were recruited and tested for aerobic power (VO(2max) 34.4 +/- 1.4 mL.kg(-1).min(-1)). During three randomly assigned 30-min test sessions, subjects functioned as their own controls and either sat in the laboratory, walked at approximately 60% VO(2max), or walked at the same treadmill speed using the BODY BAT Aerobic Exerciser. This exercise assist device resembles a pair of baseball bats seamlessly joined together and is held with both hands and swung to shoulder height across the body in a natural side to side pendulum motion. Saliva and blood samples were collected pre- and postexercise, and 1 h postexercise, with the data statistically analyzed using a 3 x 3 repeated measures ANOVA. RESULTS: Walking with the exercise assist device increased oxygen consumption 11 +/- 2% and heart rate 8 +/- 2 beats.min(-1). The pattern of increase in blood counts for neutrophils, lymphocytes, monocytes, and natural killer cells, plasma interleukin-6 concentration, and PHA-induced lymphocyte proliferation differed significantly when comparing walking with sitting, but no differences were found between walking with or without the exercise assist device. No significant increases over time or interaction effects were measured for plasma cortisol concentration, salivary IgA output, or plasma interleukin-1 receptor antagonist concentration. CONCLUSIONS: The use of an exercise assist device increased oxygen consumption 11% during walking, but did not alter the pattern of change in several components of immunity measured during walking alone in comparison to sitting. Walking caused modest and short-lived changes in immune parameters, most notably for neutrophil and natural killer blood cell counts.