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

Background and Study Aim. Ultramarathon running represents a demanding form of endurance activity characterized by prolonged duration and substantial physiological load. Despite the application of various approaches to performance assessment, the relative contribution of different physiological characteristics to race performance across standard ultramarathon distances remains a subject of practical interest. The aim of this study was to identify and directly compare the functional fitness characteristics associated with 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 the corresponding running speeds and respiratory exchange ratio (RER). Body mass index (BMI) was also assessed. Correlation and linear regression analyses were used to examine the relationships between physiological variables and race performance.
Results. The relationships between physiological variables and race performance differed between the two distances. At 50 km, performance was primarily associated with aerobic power–related variables, including VO₂max (r = 0.79), running speed at VO₂max (r = 0.82), and body mass index (r = -0.82). At 100 km, stronger associations were observed for threshold-related variables, particularly running speeds at AeT (r = 0.78) and AnT (r = 0.76), while the association with BMI was weaker (r = -0.52). Average race speed corresponded to 71.7% of vVO₂max at 50 km and 62.5% at 100 km.
Conclusions. The findings indicate a distance-dependent shift in physiological characteristics associated with ultramarathon performance. Shorter ultramarathon distances are more closely associated with aerobic power–related variables, whereas longer distances show stronger associations with threshold-related characteristics. These results support the concept of distance-specific physiological profiles in ultramarathon running. From a practical perspective, training approaches may benefit from accounting for these differences, with relatively greater emphasis on higher-intensity variables at shorter distances and threshold-related characteristics at longer distances.

This study compares functional fitness characteristics of ultramarathon runners at 50 km and 100 km distances.