A highly variable bike power file costs a measurable amount on the following run at the same average power as a steady effort, echoing pure cycling-fatigue research
Interpretation
Etxebarria et al.'s triathlon-specific trial found a 42±37s slower 9.3km run after variable-power versus constant-power cycling at identical average power, with the decrement concentrated early in the run. This is consistent with Theurel & Lepers' (2008) pure-cycling finding, already in the Bike evidence library, that variable-intensity cycling produces greater neuromuscular fatigue than constant-intensity cycling at the same average power — the same underlying mechanism showing up in both a cycling-only and a triathlon-transition context.
Practical implication
Pacing-smoothness guidance for the bike leg should cite the run-split cost directly (not just a cycling-fatigue abstraction), since that's the outcome triathletes actually care about on race day.
Sources
2 sources, independently verified.
Two 1-hour cycle trials at identical average power (variable vs. constant), each followed by a 9.3km run time trial. The run was 42±37s slower after variable-power cycling, with the performance decrement concentrated in the early stages of the run.
Two 33-min trials at identical average power — one constant (70% max aerobic power), one variable (alternating high/moderate). Neuromuscular fatigue was greater after the variable-power trial despite identical average power, directly supporting the 'surges cost more than steady riding at the same average' principle.