The Effect Of Repeated, High-volume Cycling On Circulating Immune Cells

PURPOSE: To examine the response of circulating leukocytes (WBC), lymphocytes (LY), monocytes (MO), and granulocytes (GR) to repeated, high-volume cycling. METHODS: Eight men (24 ± 4 yrs, 41.79 ± 2.49 ml/kg/min) completed an initial visit and at least 72 hours later, 90 minutes of cycling at 65%VO2max on eight consecutive days. During the initial visit, participants completed an informed consent and a maximal graded exercise test on a cycle ergometer. Participants reported to the laboratory on Day 1 and Day 8 in a fasted state. During these trials blood was collected before (PRE), immediately (IP), 30 minutes (30 M), two (2Hr), six (6Hr), and 24 hours (24Hr) after exercise. Whole blood was analyzed via an automated hematology analyzer to quantify absolute WBC, LY, MO, and GR counts. A two-way repeated measures analysis of variance (ANOVA) was used to assess differences in absolute counts between trial and time. Interactions were further explored via a one-way ANOVA across time and paired samples T-test between trials. RESULTS: No interaction for WBC (F = 2.15; p = 0.165), though a time effect was observed (F = 18.17, p < 0.001). Relative to PRE, counts were elevated (p < 0.001) at IP, recovered by 30 m; and elevated again at 2Hr and 6Hr after exercise but were recovered by 24Hr. There was an interaction between trial and time for LY (F = 5.16, p = 0.010), MO (F = 3.95, p = 0.023), and GR (F = 3.83, p = 0.049). LY counts were suppressed on Day 8 compared to Day 1 at PRE, IP, and 24Hr. MO counts were greater (p = 0.004) during Day 8 compared to Day 1 at 6Hr. GR counts were lower (p = 0.048) during Day 8 at 2Hr compared to Day 1. There were substantial changes in LY, MO and GR over time for each trial; see Table 1 for more detail. CONCLUSION: Repeated, high-volume exercise appears to alter cell mobilization. Further investigation is required to determine the subset differentiation of these changes. Table 1. - Changes in Circulating Leukocytes PRE IP 30 M 2Hr 6Hr 24Hr WBC Day 1 5.49 ± 1.01 7.65 ± 1.72* 6.07 ± 1.93 8.00 ± 2.07* 7.07 ± 1.31* 5.72 ± 1.15 Day 8 5.29 ± 1.24 7.28 ± 1.62* 5.95 ± 1.42 6.55 ± 1.28* 6.16 ± 1.07* 4.78 ± 0.85 LY Day 1 2.08 ± 0.60 2.83 ± 0.88* 1.54 ± 0.45* 1.74 ± 0.46* 1.98 ± 0.51 2.06 ± 0.59 Day 8 1.73 ± 0.61^ 2.29 ± 0.78^* 1.55 ± 0.49 1.75 ± 0.48 2.00 ± 0.48 1.69 ± 0.56^ MO Day 1 0.21 ± 0.08 0.35 ± 0.18* 0.17 ± 0.06 0.23 ± 0.08 0.15 ± 0.05 0.24 ± 0.07 Day 8 0.23 ± 0.08 0.28 ± 0.24 0.18 ± 0.11 0.22 ± 0.07 0.24 ± 0.04^ 0.19 ± 0.09 GR Day 1 3.20 ± 0.63 4.51 ± 1.03* 4.37 ± 1.75 6.03 ± 1.92* 4.93 ± 1.15* 3.44 ± 0.65 Day 8 3.37 ± 0.99 4.70 ± 1.28* 4.22 ± 1.26’8 4.61 ± 1.22^* 3.99 ± 0.80* 2.90 ± 0.59* Data are presented as mean ± SD. * different than Pre ^ different than Day 1