Full-fidelity recording, reduced display

A battery-saving pattern worth separating from the usual "low power mode" compromise: keep recording everything at full rate, and save power on the display and radios instead of on the data.

The Ultra 4's Max Extended workout mode (apple-watch) reaches ~48 hours while still logging 1-second GPS and full-rate heart rate. What it gives up: multi-band GNSS drops to single-band, the screen shows a rolling 5-minute HR average rather than live values, the always-on display goes off, and splits, alerts, and custom workouts are disabled. The Extended mode is the milder version — 20h→25h of GPS by killing the always-on display, running form metrics, and some cellular activity, with nothing else touched.

Why it's the right trade for ultra-distance: as dc-rainmaker puts it, "when I do an ultra, I don't really care about what the exact heart rate is at any point in time" — the recorded file is what gets analyzed afterward, so degrading the view costs nothing while degrading the recording would ruin the data. Contrast this with the older training-load-capture-gap failure mode, where missed capture permanently destroyed data.

Both modes are renamed and retuned versions of the old "low power" and "reduced" profiles, and were moved from deep settings to the sport profile page — a discoverability fix that matters as much as the numbers.

Note: the two launch-day reports differ slightly on the max-extended figure — 45h in rob-ter-horst's announcement analysis vs 48h here. Worth resolving against Apple's spec page or the in-depth reviews.

Sources: DC Rainmaker Ultra 4 hands-on, Quantified Scientist analysis