Between-Season Changes in the Cycling Power Profile in Relation to Training Volume and Moderate-to-High Intensity in International Junior and U23 Triathletes: A Longitudinal Study

Background: The power profile is a reliable tool for monitoring performance in the cycling segment of triathlon. This study aimed to analyze the evolution of Mean Maximal Power (MMP) in international triathletes and to examine its relationship with external load-based training characteristics. Methods: Cycling training and competition data from 14 junior and U23 international triathletes (seven males: 21 ± 1 years, 69 ± 3 kg, and 181 ± 7 cm; seven females: 22 ± 3 years, 54 ± 5 kg, and 166 ± 3 cm) were analyzed longitudinally for three consecutive seasons. The MMP from the power profile was recorded, along with the training volume accumulated in each 2.0 W·kg−1 power band. Results: All the MMP values, except values of 10 s, 30 s and 5 min, increased (p < 0.05) over the three seasons (Δ = 0.9% to 4.8%; ES = 0.30–0.47), as did the total time (Δ = 22.1%; ES = 0.42) and total distance (Δ = 32.8%; ES = 0.61). Specifically, the percentage of time spent in the 4–6 W·kg−1 power band (ES = 0.42) and MMP values for1- 20 min durations (ES = 0.25–0.47) increased (p < 0.05) from the second to the third season. MMP values ≤ 30 s showed a very large correlation (above r = 0.74) with the percentage of time spent in power bands of 12–14 W·kg−1. All the MMP values showed a negative correlation with the percentage of time spent in the 0–2 W·kg−1 power band. Conclusions: Improvements in MMP ≥ 1 min values over consecutive seasons were associated with greater total training volume and time spent in moderate-intensity power bands, whereas MMP ≤ 30 s were linked to very high-intensity power outputs.