The Influence Of Pacing Strategies On Post-race Plasma Cardiac Troponin I At The Boston Marathon

Distance racing increases the presence of circulating cardiac troponins in plasma post-race. PURPOSE: We aimed to determine a relationship between cardiac troponins and runners who over or underperformed (ran faster or slower than their entry time). We also investigated how pacing strategies affected cardiac troponin increases. METHODS: 121 runners (72 female, 49 male qualifiers, ages 18-30) entered in the 2023 Boston Marathon participated. Finish times and split times were taken from the official Boston Marathon website. Blood was sampled pre-race at the Boston Marathon Expo held Friday to Sunday prior to the race held on Monday and again 57 minutes (± 17 min) post-race. Highly-sensitive troponin I was measured in plasma along with hemoglobin and hematocrit to control for plasma volume changes during the race. Runners were split into over and underperformers by taking the ratio of their finish time and their entry time (performance ratio), runners with a ratio under one ran faster than their entry time. We assessed athletes' pacing strategies by calculating the ratio of their average speed during each race split to their overall average speed. Ratios above one indicated the runner ran faster than their average race pace during that split. Linear regressions investigated relationships between how runners paced their race and troponin I increases. Troponin I increases were log transformed due to skewness of data. RESULTS: Troponin levels increased post-race (mean = 132.86 ± 199.13 ng/L, p < 0.0001). No significant relationship existed between performance ratio and the changes in troponin I (p = 0.31). The first three splits (5 k, 10 k, 15 k) showed significant positive relationships between the split ratio and troponin I increases showing runners who chose faster starts had higher troponin increases. Later in the race, an opposite trend emerged with several splits (20 mile, 21 mile, 35 k, 23 mile, 40 k), mile markers corresponded to key points along the race course, showing a negative relationship between the split ratio and the troponin I increase. CONCLUSIONS: Boston Marathon runners who ran more conservatively at the start of the race finished faster with lower highly-sensitive troponin I increases than those who started faster. Greater strain on cardiac tissue may be related to chosen pacing strategies. Funded by the Boston Athletic Association, Boston Marathon Medical Research Funding Program 2023