Isometric thumb exertion induces B cell and T cell lymphocytosis in trained and untrained males: Physical aptitude determines response profiles

Purpose: The present study examined the effect of low-dose thumb exertion on lymphocyte subpopulation trafficking. The potential role of blood lactate in mediating lymphocyte redistribution was also investigated. Methods: 27 male participants (18 weightlifting-trained; 9 untrained) were separated into 3 groups of 9 (Weightlifting and Untrained Experimental: WLEXP, UTEXP; Weightlifting Placebo: WLPLA). WLEXP and UTEXP performed 4x60 second isometric thumb intervals separated by 60 second rest intervals in a single-blinded placebo-controlled study. Participants were assessed over a 60 minute post-intervention recovery period for pain, blood lactate and lymphocyte subpopulation counts. Results: WLPLA did not change for any measured variable (p>0.05). The two experimentalgroups increased significantly (p<0.01) in thumb pain post-intervention (WLEXP:4.92/10; UTEXP:2.92/10) however only WLEXP remained elevated across all time-points. Blood lactate increased for both experimental groups post-intervention (p<0.01) whilst peak concentrations (UTEXP: 2.2mmol/L; WLEXP: 2.4mmol/L) and temporal profiles were not different between groups (p>0.05). No differences in cell count were seen for CD56+/CD16+ lymphocytes across time for any group (p>0.05). UTEXP showed an early significant increase (20 min post-intervention) in CD4+CD3+ (20.78%, p<0.01), CD8+CD3+ (15.25%, p<0.01) and CD19+ (18.11%, p=0.013) cell count before returning to levels not different from baseline by the final time-point (p>0.05). Conversely, WLEXP group showed no early increase followed by a delayed increase in cell count evident at the final time-point; CD4+CD3+ (19.06%, p<0.01), CD8+CD3+ (11.46%, p=0.033) and CD19+ (28.87%, p<0.01). Blood lactate was not correlated with lymphocyte counts. Conclusions: Physical aptitude and not cellular energy demand influences the lymphocyte response to resistance-exercise.