Post-exercise T Cell Response Influenced By Absolute Intensity In Resistance Exercise But Not Cardiorespiratory Exercise

T cells typically mobilize in response to acute exercise. However, exercise is typically programmed using relative intensity (such as 70% of HRR or 1-RM) for participants. The PURPOSE of this study was to examine whether absolute intensity (speed, grade, total volume) influenced T cell numbers following acute exercise. METHODS: Participants were healthy older adults of a range of fitness and an average age of 63.0 ± 1.0 years (n = 24, females = 70.8%) and BMI of 24.7 ± 0.7 kg·m-2. One 30 minute bout of cardiorespiratory exercise (CRE) on a treadmill (TM) at ~70% heart rate reserve and a separate 30 minute bout of eight resistance exercises (RE) at ~70% 1-repetition maximum were conducted at least one week apart. A blood sample at rest and immediately post-exercise was collected. Multi-color flow cytometry was used for 16 T cell subsets. Subsets included CD3+, CD8+, and CD4+ naïve, central and effector memory, and cytotoxic T cells, as well as Th17 cells. Multilinear regression models were utilized to determine predictors of the exercise-induced T cell differences. All data is presented as mean pre-to-post T cell subset changes (cells/uL) ± SE. RESULTS: When including TM grade and TM speed in the model, neither predicted (p > 0.05) the post-exercise induced changes in circulating T cell counts for any of the 16 T cell subsets. However, in the RE model, total volume lifted was a significant predictor of PRE-POST increases in numerous circulating T cells, including: CD3+ (214.39 ± 48.82 cells/uL; p = 0.0232), CD4+ (126.59 ± 36.76 cells/uL; p = 0.0068), CD4 + EMRACD57+ (2.86 ± 1.23 cells/uL; p = 0.0368), CMCD4+ (48.23 ± 16.49 cells/uL; p = 0.0064), CMCD8+ (7.01 ± 2.34 cells/uL; p = 0.0384), EMCD4+ (40.70 ± 8.37 cells/uL; p = 0.0245), EMCD8+ (17.85 ± 5.16 cells/uL; p = 0.0457), and naïve CD4+ (32.25 ± 12.76 cells/uL; p = 0.0089) subsets. CONCLUSION: We observed absolute intensity to be a significant influence on exercise-induced circulating T cell changes in response to a RE bout. The influence of absolute intensity was specific to resistance exercise (total volume) and was not observed in response to cardiorespiratory exercise (speed/grade). These results support that total volume of weight lifted may need to be considered an influence when attempting to elicit exercise-induced changes to T cells for healthy older adults.