Physiological and biomechanical aspects of the first female finisher in the longest triathlon in the world - Triple Deca in Ultra Triathlon Italy 2024

Pacing in multi-day long-distance triathlons has been investigated mainly in male athletes. We analyze physiological aspects such as energy expenditure and heart rate changes as well as biomechanical aspects in swimming ( strokes per lane) and running ( stride frequency, stride length, vertical ratio, vertical movement, ground contact time) in the first and only female triathlete to finish 30 IRONMAN-distance triathlons in 30 days. The split times, lap times for swimming, cycling and running and variables were recorded with Fenix 7 Sapphire Solar with Normalized Power (NP), Intensity Factor (IF) and Training Stress Score (TSS), and were analyzed. The models' estimations for pacing were assessed with R2. Variance (ANOVA) and associative (Pearson and Spearmen) analysis were conducted at a level of significance of 5 %. Swimming pace remained stable throughout the race (linear p = 0.473), cycling pace demonstrated a significant slowdown (third-order polynomial p < 0.001), and running pace significantly improved (third-order polynomial p < 0.001). Energy expenditure slightly decreased in swimming (p = 0.099) and progressively increased for both cycling (p = 0.034) and running (p = 0.044). Moderate-intensity swimming time initially increased and later decreased, with an opposite trend for high-intensity swimming time. Cycling times at both moderate and high intensities slightly decreased. Running showed decreasing moderate-intensity time and increasing high-intensity time, consistent with improved pace. Transition times increased over the race period, with T1 increasing more prominently. Biomechanical parameters in swimming, including total stroke count and SWOLF index, showed increasing trends. Overall, significant differences were observed in running time at moderate intensity (p < 0.001, η = 0.513), high intensity (p < 0.001, η = 0.518) and average pace (p < 0.001, η = 0.603). The athlete spent significantly more time at moderate intensity (p = 0.019 and p = 0.002) and significantly less time at high intensity (p = 0.011 and p = 0.005) running in the initial phase, compared to the middle and final stages of the race. All biomechanical variables decreased slightly in the opening phase of the race but then increased in the middle and final stages of the race. Overall, the results highlight that running was the discipline most affected by physiological and pacing adaptations throughout the race; while cycling and swimming parameters demonstrated weaker or no consistent associations.