Cancer and viral-infected cells can be killed by cytotoxic (CD3+CD8+) T cells. The circulation of these cells in the body is increased in response to a single session of walking on a treadmill (TM) or resistance exercise (RE). However, it is unknown if certain variables such as TM grade, TM speed, or RE volume may have a significant impact on the exercise-induced increase of circulating cytotoxic T cells. The PURPOSEof this study is to compare, at the same relative intensity, the influence of TM grade, TM speed, and RE volume on the exercise-induced increase in cytotoxic T cells in older adults. METHODS: Healthy older adults (BMI 24.8±0.7m∙kg-2; Age 63±1.0yrs; VO240.1±2.8mL∙kg-1∙min-1) from a range of physical activity backgrounds walked on a treadmill for 30 minutes at 60-70% of their HRmax, based on the HR reserve method. Participants self-selected their TM speed, while grade of TM was adjusted to ensure participants were within their HR range. For the RE single bout, participants completed 3 sets of 8-12 repetitions at 70% of their 1RM on stacked-weight machines, also lasting approximately 30 minutes. Blood samples were collected pre-exercise (pre) and immediately post-exercise (post). These blood samples were immediately analyzed to determine cytotoxic T cell counts (CD3+CD8+) using flow cytometry (Miltenyi MACSQuant Analyzer 10). A linear mixed-effects model was used to assess the relationship between predictor variables (TM grade, TM speed, RE volume) on outcome variable (cytotoxic T cell difference between pre and post exercise), with and without potential covariates. All analyses were done in R (version 4.0.2) and data are reported as mean±SE. RESULTS: Circulating cytotoxic T cells increased in response to TM (43.3±11.9 cells/μL; p=0.0014) and RE (65.8±15.1 cells/μL; p=0.0002) bouts prescribed at the same relative intensity (TM: 60-70% HRmax; RE: 70% 1RM). When examining exercise-induced T cell increases based on absolute exercise prescription variables, TM grade (R2= 0.0005; p>0.05) or speed (R2= 0.012; p>0.05) did not contribute to increased cell counts. When examining RE, total volume lifted (4119±273kg) was also not important (R2= 0.016; p>0.05). Numerous covariates such as age, BMI, relative body fat, and weight were not significant contributors to the model. CONCLUSION: This work supports that at the same relative exercise intensity, TM speed, TM grade, and RE volume do not influence the exercise-induced increase in cytotoxic T cells. Instead, modifying relative exercise intensity may be required to cause different exercise-induced responses. Future studies should examine additional immune cell types and subtypes to confirm if the results reported in this study apply to other immune cells.
"At the Same Relative Intensity, Post-Exercise Increase of Circulating Cytotoxic T Cells is Not Affected by Resistance Exercise Volume, Treadmill Speed or Grade,"
International Journal of Exercise Science: Conference Proceedings: Vol. 2:
14, Article 58.
Available at: https://digitalcommons.wku.edu/ijesab/vol2/iss14/58