IntroductionOlder adults are at elevated risk for morbidity and mortality caused by influenza. Vaccination is the primary means of prophylaxis, but protection is often compromised in older adults. As resistance exercise mobilizes immune cells into muscle, it may enhance vaccination response.PurposeCompare antibody and cell mediated immune responses to influenza vaccination in older adults who performed eccentric resistance exercise immediately prior to vaccination to those who did not exercise.MethodsTwenty nine resistance training-naive older adults (20 women, 73.9 ± 5.3 years) were randomized to 1 of 3 groups: vaccination in the same arm that exercised (Ex-S), vaccination in the opposite arm that exercised (Ex-Op), and seated rest (No-Ex). Exercise consisted of 10 sets of 5 eccentric unilateral repetitions at 80% of the pre-determined concentric one repetition maximum. Lateral raises were alternated with bicep curls. No-Ex sat quietly for 25 min. Following exercise or rest, all received the 2018 quadrivalent influenza vaccine (Seqirus Afluria) in the non-dominant deltoid. Antibody titers against each influenza vaccine strain were determined by hemagglutinin inhibition assays at baseline, 6-, and 24-weeks post-vaccination. Influenza-specific T cells were quantified after stimulation with the vaccine by intracellular cytokine staining.ResultsNo significant group x time effects were found in antibody responses to any strain (interaction for A/H1N1: p = 0.682; A/H3N2: p = 0.644; B/Colorado/06/2017: p = 0.262; B/Phuket/3073/2013: p = 0.851). Groups did not differ in fold-increase of antibody titers 6- and 24-weeks post-vaccination. Influenza-specific T-cells did not differ between groups at any time (comparison at baseline: p = 0.985; 6-weeks: p = 0.889; 24 weeks: p = 0.857). One subject (Ex-S) reported flu-like symptoms 18 weeks post-vaccination.ConclusionAcute arm eccentric exercise did not influence antibody titers or cell mediated immune responses to the influenza vaccine delivered post-exercise in older adults. More strenuous exercise may be required for exercise to act as an adjuvant. ClinicalTrials.gov Identifier: NCT03736759.

T-cell subsets, including naïve (NA), central memory (CM), transitional memory (TM), effector memory (EM), and RA + effector memory (EMRA), differ in phenotype and function. T-cells are mobilized by exercise, with differences in the magnitude of mobilization between subsets. However, the response of TM T-cells to exercise has not yet been described. Further, T-cells expressing the late differentiation marker CD57 are known to be highly responsive to exercise, but the relative response of CD57 + and CD57- within T-cell subsets is unknown. We therefore aimed to characterize the exercise-induced mobilization of TM T-cells, as well as to compare the exercise response of CD57 + and CD57- cells within T-cell subsets.MethodsSeventeen participants (7 female; aged 18–40 years) cycled 30 min at 80% of their estimated maximum heart rate. Venous blood obtained pre, post, and 1H post-exercise was analyzed by flow cytometry. CD45RA, CCR7, and CD28 expression within CD4 + and CD8+ T-cells identified NA, CM, TM, EM, and EMRA subsets. CD57 expression within EM, EMRA, and CD28+ T-cells was also quantified. The relative mobilization of each subset was compared by calculating fold change in cell concentration during (ingress, post/pre) and after exercise (egress,1H post/post). Cytomegalovirus (CMV) serostatus was determined by ELISA and was considered in models.ResultsTM CD8+ T-cell concentration was greater post-exercise than pre-exercise (138.59 ± 56.42 cells/µl vs. 98.51 ± 39.68 cells/µl, p < 0.05), and the proportion of CD8 + with a TM phenotype was elevated 1H post-exercise (1H: 32.44 ± 10.38% vs. Pre: 30.15 ± 8.77%, p < 0.05). The relative mobilization during and after exercise of TM T-cells did not differ from NA and CM but was less than EM and EMRA subsets. Similar results were observed within CD4+ T-cells. CD57 + subsets of CD28+ T-cells and of EM and EMRA CD8+ T-cells exhibited a greater relative mobilization than CD57- subsets (all p < 0.05).ConclusionThese results indicate TM CD4 + and CD8+ T-cells are transiently mobilized into the blood with exercise, but not to as great of an extent as later differentiated EM and EMRA T-cells. Results also indicate CD57 identifies highly exercise responsive cells within CD8+ T-cell subsets.

PURPOSE:To determine whether executive function is altered during two variations of simulated microgravity head down tilt protocols. METHODS: 26 healthy volunteers (n=19 females and 7 males; 20.0 ± 1.7 years; 165.6 ± 24.5 cm; 71.1 ± 15.9 kg; mean±SD) took part in two randomly assigned separate simulated microgravity sessions consisting of 1.5 hours at -6° head down tilt (HDT) sessions. Each testing session lasted approximately 2.5 hours. One session consisted of the broadly used -6° HDT facing up (HDT-FU), while the other consisted of a -6° HDT facing down (HDT-FD) modification of the standard method. For each condition, the participant completed a computerized Stroop Color and Word Test during a thirty-minute horizontal position (0 ° tilt) prior to the interventions and again prior to the end of the 1.5-hour HDT protocols. The Stroop Color and Word Test consisted of 3 tasks (60 trials per task) including: 1) a Naming task, 2) an Inhibition task, and 3) an Inhibition/Switching task. To minimize the learning effect, both the HDT-FU and HDT-FD sessions were counterbalanced amongst all participants and were separated by a minimum of 48 hours. RESULTS: Our cognitive reaction time results demonstrate a main effect of time (pre HDT 777.60 ± 18.08ms vs post HDT 749.30 ± 19.11ms, p<0.01) and a main effect of Stroop Test (Naming < Inhibition < Inhibition/Switching, p<0.01). Additionally, we observed that the 1.5-hour protocol selectively improved the Inhibition/Switching reaction times (the most executive component) for both the p=0.02) and p<0.01). CONCLUSION: When executive demand is increased under short-term simulated microgravity head down tilt conditions, regardless of the position (face up or face down), cognitive reaction time is decreased, suggesting an improvement in overall cognitive function.

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