train · clarity · purpose

Your training.
Real signal.
No noise.

You're tracking. But is it working? Connect to Strava or drop in your activity files and Tack builds a complete picture of your fitness — VO₂ Max, FTP, training load, power zones, and more. Built for athletes who want to understand their data, not just collect it.

Get early access See what it tracks →

Connect Strava or drop in a .gpx · .tcx · .fit file

Dashboard · Last 30 days Live
VO₂ Max
58ml/kg
↑ +2.1
FTP
247W
↑ +8W
W/kg
3.4
↑ +0.1
CTL
71pts
↑ +4
TSB
+12
Fresh — ready to race
Aero eff.
2.6W/bpm
↑ +0.2
Fitness (CTL) · 42-day trend 71 pts
Power zones · last ride
Z1
Z2
Z3
Z4
Z5
Z6
Tuesday threshold intervals
NP 241W · IF 0.98 · 1h 12m · 34.2 km
87
TSS
What it tracks
Every number
that matters.
Tack calculates the same performance metrics used by TrainingPeaks, WKO5, and elite coaching staff — directly from your activity files, across every sport you train.
VO₂ Max
Estimated aerobic capacity
Hybrid Coggan + Uth formula blending power output and heart rate for accuracy across all effort types.
FTP
Functional Threshold Power
Set manually or auto-estimated from your ride history. Stamped on each ride at import for accurate historical analysis.
NP
Normalised Power
30-second rolling average raised to the 4th power — the true physiological cost of a variable-effort ride.
IF
Intensity Factor
NP divided by FTP. Tells you exactly how hard a ride was relative to your threshold.
TSS
Training Stress Score
A single number capturing both duration and intensity. The currency of training load management.
W/kg
Watts per kilogram
The universal cycling performance benchmark. Tracked over time to show real fitness progression.
VAM
Velocità Ascensionale Media
Vertical ascent metres per hour. The climber's metric — used by pro teams to benchmark climbing ability.
W/bpm
Aerobic efficiency
Power output per heartbeat. Rising W/bpm over time is a direct signal that your aerobic engine is getting stronger.
How it's built
Serious tools.
Zero friction.
📂
Import from Strava or file
Connect Strava and import your full activity history in one step — all types, all the way back. Or drop in a .gpx, .tcx, or .fit file directly. Garmin, Wahoo, and Zwift exports all work.
🔒
Completely private
Your data is stored on Tack's servers — not sold, not mined, not shared. Your rides are yours.
⚡
Stamped at import
Your weight, FTP, and Max HR are stamped onto each ride when you import it. Change your FTP later — your history stays accurate. Every metric is calculated using the values active at the time of that ride.
📊
Trends over time
Five dedicated trend charts: VO₂ Max, FTP progression, W/kg, aerobic efficiency (W/bpm), and weight. See exactly whether your training is working — across your entire ride history.
🎯
Power & HR zones
Seven power zones built from your FTP, plus HR zones using your choice of % Max HR, Karvonen (HRR), or Friel/LTHR formulas. Time-in-zone breakdown for every ride.
🗺️
Route maps & cinematic fly-through
Every ride with GPS renders as a full satellite map — switchable between satellite, terrain, and street views with 3D terrain. Hit play for a cinematic fly-through of the route at full screen.
🤖
AI coaching
Tack is building an AI layer that interprets your training patterns in plain English — telling you what your signals mean and what to do next to keep getting fitter. Coming soon.
🔬
Auto-detect thresholds
Can't test your FTP? Tack estimates it from your hardest efforts in your ride history. Auto-detects your Max HR the same way — no lab required.
Ride detail
Every ride,
fully decoded.

Import a file and Tack breaks it into every meaningful number — not just distance and time, but the performance data that actually tells you how the ride went and what it cost you.

GPS rides also render as a full satellite route map with terrain and street views, plus a cinematic fly-through you can play back at full screen. Each metric is calculated using the FTP, weight, and heart rate values active at the time of that ride — so your history stays accurate even as your fitness evolves.

Tuesday threshold intervals
14 Jan 2025  ·  72 km  ·  2h 14m  ·  840 m gain
87
TSS
Power
241
NP (W)
228
Avg (W)
614
Max (W)
0.98
IF
3.4
W/kg
Heart rate
158
Avg (bpm)
179
Max (bpm)
2.6
W/bpm
58
VO₂ est.
Cadence
86
Avg (rpm)
118
Max (rpm)
Climbing
840
Gain (m)
1,140
VAM (m/h)
Time in power zones
Z1
Z2
Z3
Z4
Z5
Z6
18m
38m
26m
44m
6m
2m
Training Load
Fitness. Fatigue. Form.
All in one view.
The same Banister impulse-response model used by TrainingPeaks and WKO5 — calculated correctly with a full recursive daily walk across your entire ride history.
CTL
Fitness
42-day avg. training stress
Your aerobic baseline. Rises slowly as you build consistent training, falls slowly when you rest. A CTL of 80 means your body handles roughly 80 TSS/day sustainably. Beginners: 20–40. Amateurs: 50–80. Racers: 80–120+.
ATL
Fatigue
7-day avg. training stress
How hard you've trained in the last week. Spikes fast after big efforts, drops fast after rest. High ATL isn't bad — fatigue is how you build fitness. Racing into high ATL without recovery is the mistake to avoid.
TSB
Form
CTL minus ATL
Are you fresh or tired right now? Positive TSB means fitness is outrunning fatigue — you're primed to perform. Negative means you're carrying load. The sweet spot before a race: +5 to +25, achieved with a 7–10 day taper.
File support
Works with
what you already export.
.fit
Garmin FIT binary
The native format from Garmin Edge computers, Wahoo, and most modern head units. Parsed natively — no conversion needed. Full power, HR, cadence, and GPS streams.
.gpx
GPS Exchange Format
The universal GPS format — exported by Strava, Komoot, Ride With GPS, and most platforms. Supports Garmin TrackPoint extensions for power and heart rate data.
.tcx
Garmin Training Center XML
Garmin's structured training format. Full support for power, HR, cadence, elevation, distance, and lap data. Used by older Garmin devices and Zwift exports.
Integrations
Oura Ring
Ultrahuman
Apple Health
Strava ✓ Live
Garmin Connect
Tonal
Resting HR · strength training · auto-import · coming soon
Getting started
Three steps
to your first insight.
01
Set your athlete profile
Enter your weight, FTP, resting HR, and max HR. Or leave them blank — Tack will auto-estimate from your first import. Everything auto-saves as you type.
02
Connect Strava or drop in files
Connect Strava to import your full activity history in one go — all types, filtered by date range and sport. Or drag and drop individual .gpx, .tcx, or .fit files. GPS maps load in the background automatically.
03
Watch the signal emerge
Your dashboard populates immediately. CTL/ATL/TSB, VO₂ Max trend, FTP progression, zone breakdowns — the fuller your history, the more precise the picture.

train · clarity · purpose

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