Objectives: This study aimed to investigate whether measures of cardiopulmonary fitness and rela-tive exercise intensity were associated with high sensitivity cardiac troponin T (cTnT) rise after a roadmarathon.Methods: Fifty-two marathon runners (age 39 ± 11 years, body mass 76.2 ± 12.9 kg, height 1.74 ± 0.09 m)attended the laboratory between 2 and 3 weeks prior to attempting the Brighton Marathon, UK. Runningeconomy at 10 km h-1(RE10) and race pace (RERP), ventilatory threshold (VT) and VO2max tests werecompleted. CTnT was measured within 48 h prior to the marathon and within 10 min of completing themarathon, using a high sensitivity assay. Heart rates (HR) were recorded throughout the marathon.Results: Runners demonstrated a significant increase in cTnT over the marathon (pre-race5.60 ± 3.27 ng L-1, post-race 74.52 ± 30.39 ng L-1, p < 0.001). Markers of endurance performancesuch as running economy (10 km h-1223 ± 18 ml kg-1km-1; race pace 225 ± 22 ml kg-1km-1), VT(38.5 ± 6.4 ml kg-1min-1) and˙VO2max (50.9 ± 7.7 ml kg-1min-1) were not associated with post-racecTnT. Runners exercise intensity correlated with post-race cTnT (mean HR %VT 104 ± 5%, r = 0.50; peakHR %VT 118 ± 8%, r = 0.68; peak HR %˙VO2max 96 ± 6, r = 0.60, p < 0.05) and was different between the low,medium and high cTnT groups (p < 0.05).Conclusions: CTnT increases above reference limits during a marathon. Magnitude of cTnT rise is related toexercise intensity relative to ventilatory threshold and˙VO2max, but not individuals' absolute cardiopul-monary fitness, training state or running history.