Functional fitness characteristics of ultramarathon runners specialized in 50 km and 100 km distances

Abstract

Background and Study Aim. While ultramarathon running is gaining global popularity, current training methodologies often treat all distances beyond a marathon as a single physiological category. This study addresses the knowledge gap regarding distance-specific performance determinants by analyzing the "metabolic shift" between 50 km and 100 km races. The aim is to define the functional fitness characteristics of ultramarathoners and assess their specific impact on race performance at 50 km and 100 km distances. Materials and methods. Thirty-one experienced ultramarathon runners performed an incremental treadmill test to volitional exhaustion to determine maximal oxygen uptake (VO2max), aerobic threshold (AeT), anaerobic threshold (AnT), and their corresponding speeds and respiratory exchange ratios (RER). Body mass index (BMI) was also calculated. Correlation and linear regression analyses were conducted to evaluate the relationship between these variables and race finishing times. Results. The physiological predictors of performance differed significantly between the two distances. For the 50 km distance, VO2max, speed at VO2max, and body mass index (BMI) were the strongest predictors of race time. Conversely, for the 100 km distance, metabolic economy played a primary role, with speed at AeT and speed at AnT showing the most significant correlations, while the impact of BMI decreased. Average race speed corresponded to 71.7% of VO2max speed for 50 km and 62.5% for 100 km. Conclusions. The transition from a 50 km to a 100 km ultramarathon is characterized by a significant shift in physiological demands. While 50 km performance relies heavily on aerobic power (VO2max) and optimal body composition (BMI), 100 km success is primarily determined by metabolic efficiency and aerobic threshold speed. Consequently, training programs must be highly distance-specific: 50 km athletes should prioritize high-intensity intervals, whereas 100 km runners should focus on high-volume, low-intensity training (polarized approach) to optimize fat oxidation and aerobic threshold speed.