Discussion
HIE, DOMS, muscle damage, MP
ADVERSE EVENTS, SECONDARY, OXIDATIVE STRESS
Significant changes in biomarkers occurred following HIE, indicating an overall profound effect on the inflammatory and immune system. While there were limited differences in biomarker response between supplementation conditions, a notable difference in cytokine changes occurred with UPF compared to placebo, which may have implications for recovery. Interestingly, the inflammatory and immune system responses following both supplementation conditions were generally similar between males and females (with the exception of IL-1β and neutrophils), suggesting no apparent differences between sexes. Importantly, no adverse events were reported throughout the study period, indicating a positive safety profile of UPF.IL-6 production is proportional to exercise intensity [The inflammatory cytokine response immediately following HIE could be related to the significant changes in WBC, specifically CD4 and CD8 cells, observed with both conditions. Since CD4 cells are cytokine-signaling T-cells [The secondary hypothesis of improved exercise performance was not supported as no significant PP or MP differences were observed between groups. These results indicate that fucoidans may not act as a direct ergogenic aid to improve performance during acute bouts of HIE. However, unlike the current study, consistently lowered chronic inflammatory markers and improved immune health have been demonstrated in previous research in healthy [To the authors’ knowledge, this is the first study using fucoidan supplementation as a strategy to impact cytokine and immune cell response following an acute bout of HIE in a human model using a trained population. Importantly, the responses of both males and females were included as a part of this evaluation. As noted, males and females responded similarly to supplementations. However, IL-1β showed a significant sex-by-condition interaction, with no differences seen as a function of UPF supplementation in females. Males experienced higher IL-1β concentrations in the PL condition compared to UPF. Interestingly, there was a sex-by-time interaction for neutrophils by which females experienced greater neutrophil concentrations at timepoint B and D compared to A, whereas males only experienced greater concentrations at timepoint B. The mechanisms behind this interaction may require further investigation, but these findings highlight the importance of considering sex effects in the area of performance nutrition and physiology.A major strength of the present research is the double-blind, placebo-controlled, counterbalanced, crossover design. All participants partook in both arms of the study with identical procedures for S1/S2 and T1/T2. Additionally, T1/T2 controlled for time of day to account for diurnal rhythms, required no MIE or HIE within 24 h of the testing sessions to avoid superficial inflations of biomarkers, and diet was matched for each participant in the 24 h leading into the testing sessions. Supplementation order was used as a covariate in order to mitigate the effects of familiarization with the HIE protocol between T1 and T2.However, there are some limitations. Firstly, this research investigated a single acute bout of HIE after 2 weeks of supplementation. Therefore, chronic adaptations and performance changes with supplementation cannot be determined. Future research with longer supplementation periods is warranted to determine the effects on HIE performance and adaptation. Additionally, since the current research investigated the recovery period during a single HIE bout, future research should investigate if fucoidan supplementation could improve recovery status over multiple HIE bouts when rest periods are limited. Importantly, the degree of muscle damage following the HIE bout could not be ascertained by the peripheral inflammatory and immune blood biomarkers assessed in this study. Although this HIE protocol was used previously to induce DOMS and oxidative stress after exercise [In this study, HIE induced a profound inflammatory and immune system response that persisted throughout the 1-h post-exercise evaluation period. Supplementation with UPF resulted in limited differences in biomarker response with the exception of cytokines. Both IL-6 and IL-10 increased compared to placebo during the 30-min recovery period. Though not statistically significant, the pattern of decreased IL-1β concentrations by 1-h post exercise with supplementation compared with increases seen with PL may indicate a greater anti-inflammatory environment occurring with UPF. Given the differential changes in cytokines occurring during the recovery period, longer supplementation periods (>2 weeks) along with a longer duration of measurement following HIE may be warranted to see additional effects.