Engine room · power / HR — Cash in your flat-road diesel — O2 isn't the limiter yet. Hold power, tuck the false flats, don't let the hot Kona coast float your HR. Be brave HERE, not up top.
Sustained tempo · power / HR — The Saddle grind — the metronome is the whole game. Even effort, keep eating and drinking hard while the gut still works.
Air thinning · power / HR → breath — Last stretch where HR tells the truth. Top off both bottles and pocket food before the VIS.
Altitude bites · breathing / RPE — Cinder and thin air. STOP watching watts — they'll look sad and that's correct. Breath-pace, stay seated, never punch a steep ramp.
Survival grind · breathing / RPE — Watts are meaningless now, effort is everything. Tiny circles, steady breath, eyes up the road. If HR won't climb, that's the ceiling, not you.