This single-blind and cross-sectional study evaluated the role of Rho-kinase (ROCK) as a biomarker of the cardiovascular remodelling process assessed by echocardiography in competitive long-distance runners (LDR) during the training period before a marathon race. Thirty-six healthy male LDR (37.0±5.3 years; 174.0±7.0 height; BMI: 23.8±2.8; VO2-peak: 56.5±7.3 mL·kg-1·min-1) were separated into two groups according to previous training level: high-training (HT, n=16) ≥100 km·week-1 and low-training (LT, n=20) ≥70 and <100 km·week-1. Also, twenty-one healthy nonactive subjects were included as a control group (CTR). A transthoracic echocardiography was performed and ROCK activity levels in circulating leukocytes were measured at rest (48-hr without exercising) the week before the race. HT group showed higher left ventricular mass index (LVMi) and left atrial volume index (LAVi) than other groups (p<0.05, for both), also higher levels of ROCK activity were found in LDR (HT=6.17±1.41 vs CTR=1.64±0.66 (p<0.01); vs LT=2.74±0.84; (p<0.05)). In LDR a direct correlation between ROCK activity levels and LVMi (r=0.83; p<0.001), and LAVi (r=0.70; p<0.001) were found. In conclusion, in male competitive long-distance runners, the load of exercise implicated in marathon training is associated with ROCK activity levels and the left cardiac remodelling process assessed by echocardiography.