Adaptation to eccentric exercise: effect on CD64 and CD11b/CD18 expression

Abstract

The primary purpose of the study was to examine circulating neutrophils and monocytes and their plasma membrane expression of CD64, CD11b, and CD18 after two bouts (B1 and B2) of eccentric exercise. Subjects (n = 10) performed 25 forced-lengthened contractions of the forearm flexors on two occasions separated by 3 wk. Blood samples were obtained before exercise and at 1.5, 6, 12, 24, 48, 72, and 96 h of recovery. CD64, CD11b, and CD18 expression was determined via direct immunofluorescence and used as an indicator of neutrophil and monocyte activation. Creatine kinase activity (B1 = 1,390, B2 = 108 U/l), myoglobin (B1 = 163, B2 = 41, ng/dl), and muscle soreness and tenderness were higher (P < 0.01) after B1 compared with B2. Neutrophils at 6, 12, and 96 h were higher (P < 0.05) for B1 vs. B2. CD11b expression on neutrophils was 2.7-fold higher at 72 h for B1 vs. B2. CD64 expression on neutrophils at 72 and 96 h was 1.4- and 1.9-fold higher, respectively, for B1 vs. B2. At 72 and 96 h, CD18 and CD64 expression on monocytes was 1.3-fold higher for B1 vs. B2. The observed changes were not significantly correlated with changes in creatine kinase activity or myoglobin. In conclusion, the adaptation to eccentric arm exercise was associated with a reduction in circulating neutrophils and a lower state of neutrophil and monocyte activation.

Repeated muscle damage blunts the increase in heat strain during subsequent exercise heat stress

“…An elevated circulating IL-6 prior to heat stress is significant, given a potential involvement of the acute inflammatory response in the aetiology of EHI (Bouchama 1995;Lim and Mackinnon 2006;Shephard and Shek 1999;Walsh et al 2011). A "dampening" of the inflammatory response is one proposed explanation for the repeated bout effect (Pizza et al 1996). Indeed, a previous study has shown reduced pro-inflammatory cytokines (IL-6), and increased anti-inflammatory cytokines (IL-10) in the 12 hours following a repeated bout of muscle damage evoked by downhill running (Smith et al 2007), although this finding is not supported by studies that have used different models of muscle damage (e.g.…”

“…In our previous study (Fortes et al 2013), increased circulating interleukin (IL)-6 concentration following EIMD was associated with increased heat strain during subsequent exercise heat stress, a pertinent finding due to a potential inflammatory role in the aetiology of EHI/EHS (Bouchama 1995;Lim and Mackinnon 2006;Shephard and Shek 1999). A dampening of the inflammatory response is one proposed explanation for the repeated bout effect (Pizza et al 1996), and given that there is some evidence that circulating IL-6 concentration is reduced following a second, repeated bout of EIMD compared with the first bout (Smith et al 2007) this may provide a mechanism for a potential beneficial repeated bout effect in reducing heat strain.…”

Changes in neutrophil count, creatine kinases and muscle soreness after repeated bouts of downhill running

“…16 Although acute inflammation promotes healing, an undesirable 'side-effect' of this process involves the release of catabolic substances that inadvertently degrade surrounding healthy tissue. Pizza and colleagues 18,19 have suggested that the repeated bout effect may be related to Conclusion. The lack of significance in neutrophils, as well as the early onset of difference in CK between run 1 and run 2 were attributed to the type of eccentric protocol used.…”

“…However, a primary difference between the two studies was the exercise protocol. Pizza et al 18,19 used highintensity, low-volume resistance-like eccentric contractions of the elbow flexors, while the aforementioned study 21 used repeated bouts of downhill running, which incorporated lowintensity high-volume aerobic-like eccentric contractions. An alternate reason for the lack of consensus between these studies could have been that in the previous downhill running study, 21 the intensity, the steepness of the gradient and the duration of the running bouts were not sufficiently strenuous.…”

“…With regard to repeated bouts of eccentrics, CK has consistently been shown to be significantly lower after the second bout of eccentrics. 3,8,14,18,21 However, in previous downhill running studies 3,5,21 CK was only measured at 24-h intervals; whether differences in serum CK are evident at an earlier time point after downhill running has not been investigated. Thus, an additional purpose of this study was to assess total circulating CK at 3-h intervals during the initial 12 h, as well as at 24-h intervals for 6 d, following both downhill runs.…”