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Eliott Arroyo, MS – PhD Candidate, Kent State University

Emily C. Tagesen – Graduate Assistant , Kent State University

Tricia L. Hart, CSCS – n/a, n/a

Brandon A. Miller, CSCS – Graduate Student, Kent State University

Adam R. Jajtner


PURPOSE: To compare the effects of high-intensity interval training (HIIT), sprint interval training (SIT), and moderate-intensity continuous training (MCT) on lymphocyte subset populations. METHODS: Recreationally active men (n=3; 21.3±3.5 yrs; 182.8±6.3 cm; 79.4±8.7; 11.2±5.8 %BF; 44.1±3.2 ml·kg-1·min-1) completed a maximal graded exercise test (VO2max) and three exercise trials (HIIT, SIT, and MCT) in a randomized, counterbalanced fashion on a cycle ergometer. HIIT consisted of fifteen 90-second bouts at 85% VO2max interspersed with 90-second active recovery periods. SIT consisted of fifteen 20-second bouts at 130% maximum wattage interspersed with 160-second active recovery periods. MCT was a continuous bout at 65% VO2max. Each trial lasted 53 minutes, including a 5-minute warm-up and a 3-minute cool-down. Blood was collected before (PRE), immediately post (IP), 30 minutes (30P), 2 hours (2H), 6 hours (6H) and 24 hours (24H) post-exercise. The number and percentage of lymphocyte subsets (CD3+CD4+, CD3+CD8+, CD3CD56brightCD16-, CD3CD56dimCD16+, and CD3−CD19+) were analyzed via flow cytometry. Total lymphocyte count was analyzed via hematology analyzer. Changes were assessed using a two factor (time × trial) within-subjects repeated measures ANOVA. RESULTS: A significant time × trial interaction was observed for CD3+CD4+ percentage (F=2.989, p=0.018) and count (F=2.653, p=0.030). CD3+CD4+ count decreased from PRE to 24H in both MCT (p=0.007) and SIT (p=0.030), but not HIIT (p > 0.05). During HIIT, CD3+CD4+ count was increased from PRE to IP (p=0.008). A significant time × trial interaction was observed for CD3+CD8+ (F=4.909, p=0.001) and CD3-CD19+ counts (F=2.536, p=0.037). CD3+CD8+ count was elevated at 6H compared to 2H in both MCT (p=0.016) and HIIT (p=0.032), but not SIT. For HIIT, CD3-CD19+ count was greater at IP relative to PRE (p=0.019), 30P (p=0.033), and 24H (p=0.041). A significant time × trial interaction was observed for CD3-CD56brightCD16- count (F=6.010, p< 0.001). At IP, CD3-CD56brightCD16- count was greater for HIIT compared to MCT (p=0.017) and SIT (p=0.013).  A significant time × trial interaction was observed CD3-CD56dimCD16+ percentage (F=4.206, p=0.003) and count (F=3.203, p=0.013). For SIT, CD3-CD56dimCD16+ count was lower at 2H compared to PRE (p=0.047). CONCLUSION: Data suggest that both SIT and MCT, but not HIIT, elicited a decline in CD3+CD4+ count 24 h following exercise. HIIT and MCT triggered a significant increase in CD3+CD8+ count at 6H that was not observed following SIT. CD3-CD19+ count was elevated at IP following HIIT, but not following SIT or MCT. CD3-CD56brightCD16- count was significantly greater immediately after HIIT compared to SIT and MCT. CD3-CD56dimCD16+ count declined 2 h following SIT but not following HIIT or MCT. PRACTICAL APPLICATIONS: The results of this study suggest that, despite identical duration, HIIT, SIT, and MCT elicit dissimilar immune responses. T helper cells (CD3+CD4+), which play an important role in immune function, appear to be suppressed following SIT and MCT, but not HIIT. Cytotoxic NK cells (CD3-CD56dimCD16+) were depleted 2 h following SIT, but not following HIIT or MCT, indicating potential susceptibility to infection following SIT. Further research is needed to determine the practical effects of varying exercise intensities on immune function.


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