Application of heart rate monitoring for assessing the intensity of training loads in speed–strength sports: a case study of combat sports

<jats:p>Objective. The purpose of this study was to critically evaluate the effectiveness of heart rate (HR) monitoring as a method for assessing the intensity of sport-specific training loads employed in combat sports. Materials and Methods. The study involved highly qualified members of the Russian National Karate Team (WKF Kumite). The participants completed three standardized blocks of sport-specific exercises: (1) repeated high-intensity speed-oriented alactic anaerobic exercises consisting of five maximal-effort bouts separated by one-minute recovery intervals; (2) a simulated competitive bout with standardized attacking sequences (2 min for female athletes and 3 min for male athletes); (3) official sparring bouts conducted under WKF competition rules. Peak heart rate was recorded using Polar heart rate monitors, while blood lactate concentration was determined from capillary blood samples. Correlation analysis revealed no statistically significant relationship between post-exercise heart rate and blood lactate concentration (r = 0.22). Results. The findings demonstrated that maximal or post-exercise heart rate values do not adequately reflect either the actual intensity or the metabolic cost of high-intensity sport-specific exercises performed in combat sports. The weak correlation between heart rate and blood lactate concentration confirms the limited applicability of conventional heart rate–based training zones for monitoring predominantly anaerobic exercise. Conclusions. A linear relationship between heart rate and exercise intensity exists only within a relatively narrow range of predominantly aerobic exercise intensities up to approximately 0.75 of the maximal metabolic rate, (MMR), representing less than 5% of the total spectrum of training loads encountered in combat sports. For the quantification of speed–strength training loads, the cumulative heart rate cost of exercise (including both exercise and recovery periods) is proposed as a more informative physiological indicator, owing to its close association with oxygen demand and the overall energetic cost of exercise.</jats:p>