doi:10.23736/S0022-4707.20.10860-0engCalleja-Romero, A.López-Laval, I.Sitko, S.Hernando, D.Vicente-Rodríguez, G.Bailón, R.Garatachea, N.Effects of a 75-km mountain ultra-marathon on heart rate variability in amateur runnersART-2020-121254BACKGROUND: This study examined the effects of a mountain ultra-marathon (MUM) on the activity of the autonomous nervous system through heart rate variability (HRV) monitoring and determined whether this variable related to final performance. METHODS: Heart rate and HRV were measured in eight male amateur runners (aged 37-60 years). Measurements were recorded before and after the event, in resting conditions, as well as continuously throughout the whole MUM. In addition, percentage (%) of heart rate reserve (HRres) and partial and total times during the race were analyzed. RESULTS: Average heart rate (HRavg) measured at rest was increased after the event (+37%). Standard deviation of successive differences (SDSD) and the square root of the mean squared differences of successive NN intervals (RMSSD) were reduced after the MUM (-56% and -59%, respectively). There was a positive relationship between the frequency-domain index normalized low frequency power (PLFn) measured at rest before the event and race time (0.79) while there was a negative relationship between race time and the difference in HRavg before and after the event. In the last half of the event, there was a high correlation (Spearman coefficient of correlation >0.9) between race time and the standard deviation of the NN intervals (SDNN) registered during the race. CONCLUSIONS: Autonomous cardiac regulation can be related to the performance in a mountain ultra-marathon. HRV monitoring could represent a practical tool for the evaluation of the relationship between the autonomous nervous system activity and performance in a mountain ultra-marathon.2020http://zaguan.unizar.es/record/10833710.23736/S0022-4707.20.10860-0http://zaguan.unizar.es/record/108337oai:zaguan.unizar.es:108337The Journal of sports medicine and physical fitness 60, 10 (2020), 1401-1407All rights reservedhttp://www.europeana.eu/rights/rr-f/info:eu-repo/semantics/openAccess