4. Discussion
heart and skeletal muscle, fatigue, Fatigue
CONTRACTION
The primary aim of this study was to confirm the effects of LC-Plasma on fatigue caused by a continuous high training load. All the participants in this study belonged to the same sports club. Since the participants had had 3 days of rest without exercise before the start of the test, it is considered that the fatigue state at the start of the experiment was stable. During the intake period of continuous exercise, the average intensity of exercise of the 31 participants was 13.2 ± 2.8 MET-h/day. This is higher than the intensity in our previous study (12.4 ± 3.9 MET-h/day). It has been reported that individuals who run more than 14 km per day (approximately 14 MET-h/day) are more susceptible to URTI [Our results suggested that the CD86 of pDCs in the LC-Plasma group was significantly higher than the level found in the PL group after continuous exercise. The HLA-DR in pDCs significantly decreased in the PL group only in the intragroup comparison. As for the sense of fatigue, cumulative days of fatigue in the participant diary significantly decreased in the LC-Plasma group. The scores of Fatigue–Inertia in POMS2 and “Are you tired?” in VAS showed a worsening trend in the PL group only. These results are similar to those of our previous study [We also assessed the effects of LC-Plasma intake on the objective indices (TGF-β, IL-6, cathepsin L, adrenaline, 8-OHdG, testosterone, leptin, and CPK) associated with fatigue. Some factors in the hematological indices were significantly changed in the intragroup comparison after both the continuous and single exercise; however, no significant difference was observed between the groups. Adrenaline was the index that changed after both the continuous and single exercise in the intragroup comparison. Adrenaline is released with exercise and helps the body to resist stress conditions. It affects the cardiovascular system, producing a rapid powerful vasopressor effect, and increasing heart rate, the force of contraction, the respiratory rate, and blood flow towards the brain, heart and skeletal muscle [We also performed a short-term single exercise test after the continuous exercise for the purpose of assessing the impact of LC-Plasma on fatigue in more detail. However, no significant difference in CD86, HLA-DR, or subjective analysis of fatigue was observed in the intergroup comparison. This may be due to the insufficient intensity of the single exercise session, because no change in CPK was observed. However, it should be noted that in the index of the sympathetic and parasympathetic autonomic balance, the LF/HF value was significantly low and improved in the LC-Plasma group after the single exercise session, although no significant difference was detected between the groups after the continuous exercise. LF/HF has been reported to be linked with fatigue [We set the target sample size at 20 subjects in each group, when the power was set at 0.8 based on the results of CD86 expression of previous experiments. As a result of the final sample size of each group being 15 and 16 due to the exclusion of participants, the standard deviation was larger than in past measurements. Therefore, the power of this experiment was 0.6, which was lower than expected. A larger number of subjects may have been required for a more appropriate LC-Plasma evaluation.There are some limitations to this study that may affect the results. The subjects were limited to athletes aged around 20 years, who performed exercise routinely. The intensity of exercise was also limited. The tracing of lifestyle factors such as meal records, heart rate, and blood pressure during the study period are insufficient to omit the possibility of confounders. In addition, since the short-term single exercise was performed the day after the end of the continuous exercise, it is possible that the influence of the continuous exercise on the subject’s fatigue accumulation cannot be completely excluded.In the future, further studies are needed with participants from more diverse backgrounds, at a more appropriate timing, with stricter lifestyle controls, and with more hematological investigations to reveal the impact of LC-Plasma on fatigue.