Muscle and intestinal damage in triathletes

The aim of the paper was to assess indicators of muscle and intestinal damage in triathletes. The study involved 15 triathletes whose objective for the season was to start in the XTERRA POLAND 2017 event (1,500-m swimming, 36-km cycling, and 10-km mountain running). Before the 14-week preparatory period, the competitors’ body composition was measured, aerobic capacity was tested (graded treadmill test) and blood samples were collected to determine markers showing the level of muscle and intestinal damage. Subsequent tests for body composition were carried out before and after the competition. Blood samples for biochemical indicators were collected the day before the competition, after the completed race, and 24 and 48 hours later. A significant decrease in body mass was observed after completing the race (–3.1±1.5%). The mean maximal oxygen uptake level among the studied athletes equalled 4.9±0.4 L·min–1, 58.8±4.5 mL·kg–1·min–1. The significant increase in concentrations of cortisol, c-reactive protein and myoglobin after the competition, significantly correlated with the significant increase in zonulin concentration (post 1h: r = 0.88, p = 0.007, r = 0,79, p = 0.001, r = 0.78, p = 0.001, and post 12h: r = 0.75, p = 0.01, r = 0.71, p = 0.011, r = 0.83, p = 0.02). No significant changes in the concentration of tumour necrosis factor alpha among the examined competitors were noted at following stages of the study. The results of our research showed that in order to monitor overload in the training of triathletes, useful markers reflecting the degree of muscle and intestinal damage include cortisol, testosterone, testosterone to cortisol ratio, c-reactive protein, myoglobin and zonulin. Changes in muscle cell damage markers strongly correlated with changes in zonulin concentration at particular stages of the study. Thus, one can expect that the concentrations of markers depicting the level of muscle cell damage after an intense and long-lasting effort will significantly influence the level of the intestinal barrier.

本研究旨在评估铁人三项运动员的肌肉与肠道损伤相关指标。研究纳入15名赛季目标为参加2017年XTERRA波兰赛事（该赛事设置1500米游泳、36公里自行车骑行与10公里山地跑项目）的铁人三项运动员。在14周备赛周期启动前，研究人员测量了受试者的身体成分，开展递增负荷跑台试验（graded treadmill test）以评估有氧能力，并采集血液样本以检测反映肌肉与肠道损伤水平的标志物。后续身体成分测量分别于赛前及赛后进行。用于生化指标检测的血液样本分别于赛前1日、完赛即刻以及赛后24小时、48小时采集。研究观察到，完赛后受试者体重出现显著下降（降幅为-3.1±1.5%）。受试运动员的平均最大摄氧量分别为4.9±0.4 L·min⁻¹与58.8±4.5 mL·kg⁻¹·min⁻¹。赛后皮质醇、C反应蛋白（C-reactive protein）与肌红蛋白浓度均显著升高，且各指标的变化与连蛋白（zonulin）浓度的升高呈显著相关：赛后1小时，三者与连蛋白的相关系数依次为r=0.88（p=0.007）、r=0.79（p=0.001）、r=0.78（p=0.001）；赛后12小时，相关系数依次为r=0.75（p=0.01）、r=0.71（p=0.011）、r=0.83（p=0.02）。本研究各阶段中，未观察到受试受试者肿瘤坏死因子-α（tumour necrosis factor alpha）浓度出现显著变化。本研究结果表明，若要监测铁人三项运动员训练中的负荷过载情况，可用于反映肌肉与肠道损伤程度的有效标志物包括皮质醇、睾酮、睾酮/皮质醇比值、C反应蛋白、肌红蛋白及连蛋白。在本研究的各阶段中，肌肉细胞损伤标志物的变化与连蛋白浓度的变化呈强相关性。由此可推测，在高强度、长时间运动后，反映肌肉细胞损伤水平的标志物浓度会对肠道屏障功能产生显著影响。