Cardiovascular drift measurably erodes the power sustainable at a given physiological intensity as heat and duration climb, meaning a cool-weather FTP overstates what's achievable on a hot race day
Interpretation
Wingo et al. established that cardiovascular drift (rising heart rate / falling stroke volume at a fixed workload) under heat stress is directly related to a measurable reduction in achievable VO2max. Lafrenz et al.'s follow-up confirmed this scales with ambient temperature rather than being a fixed, duration-only effect — together showing that both duration and heat independently erode what a given power output actually costs physiologically.
Practical implication
Race-day power targets derived from a cool-conditions FTP test should be adjusted downward for heat, with the adjustment scaled to expected race-day temperature, not treated as a fixed multi-hour-duration-only discount.
Sources
2 sources, independently verified.
MSSE 37(2):248-255. Cardiovascular drift (the progressive heart-rate rise / stroke-volume decline at a fixed workload) during heat stress is directly related to a measurable reduction in achievable VO2max — a physiological basis for why a cool-weather FTP or threshold test overstates what's sustainable in race-day heat.
MSSE 40(6):1065-1071. Extends Wingo et al. (2005) by varying ambient temperature directly, confirming cardiovascular drift's effect on maximal oxygen uptake scales with heat stress rather than being a fixed, duration-only phenomenon.