Every ski culture has the same proverb: it’s always the last run. Like most proverbs it’s part truth, part survivorship — any run you get hurt on becomes your last run by definition, which makes the saying unfalsifiable as stated. But underneath the folk statistics sits a real mechanism worth taking seriously: fatigue changes how you ski before you notice it, and the change is measurable from your pocket.
Skiing is eccentric exercise — muscles lengthening under load, which is precisely the contraction type that fatigues quadriceps fastest and shows up as degraded control rather than felt exhaustion. You don’t feel 20% weaker at 3pm; you just turn less.
That’s the signature a phone can see. A rhythm of linked turns is a choice that costs energy; straight-lining and long lazy arcs are what legs vote for when the tank empties. Turn cadence — turns per minute, per run — falls as the day wears on, and it falls before you’d call yourself tired, because your brain economizes movement long before it files a complaint.
Each run’s turn count is estimated from GPS heading swings (sustained 30° course reversals — an estimate, labeled as one, and systematically a little low for tight turns). Dividing by run duration gives cadence, and the Day Rhythm chart plots it run by run across your day.
Two honesty rules govern what the chart is allowed to claim:
There’s a known confounder the app states in-copy: terrain moves cadence too. A steep couloir skis at a different rhythm than a motorway groomer, so a day of varied terrain adds noise to the trend. The signal survives for most days — you mostly lap similar terrain, and the within-day decline is what the verdict reads — but the caveat stays printed under the chart, because deleting caveats is how instruments become marketing.
If you ski with an Apple Watch, your heart rate for the day is already in Apple Health, and Alpy can read it — with your permission, read-only, displayed and never stored — and lay per-run averages alongside the cadence story. The combination is where it gets interesting:
So should you skip it? The honest chain of reasoning: fatigue demonstrably degrades motor control; degraded control on skis raises the chance of the error classes that hurt (catching an edge, late weight shift, the knee-twisting backseat recovery); and fatigue peaks at day’s end — which is also when light flattens and pistes are scraped to their icy base by ten thousand earlier edges. Mechanism stacked on mechanism, all pointing the same way, no fake precision required.
The useful reframe: the question isn’t “is the last run cursed?” It’s “am I skiing my 10am standard right now?” — and that’s a question your own data can actually answer. If your cadence has faded a fifth since morning and your legs are negotiating rather than carving, the mountain will be there tomorrow. Check the Day Rhythm chart on the lift. If the curve has sagged, let that be the last run — the one you watched happen, instead of the one that happened to you.
Day Rhythm, per-run cadence and Apple Watch effort readouts are free in Alpy. Nothing leaves your phone. The app · More from the blog.