Assuming an official rate
The official description connects treadmill use to speed and biomes but does not publish one universal gain rate.
Measure a one-minute treadmill sample, estimate time to a personal speed goal, and follow the biome requirement shown in your current game.
Follow the visible current-game loop, measure values that vary by player, and stop where the game has not exposed a reliable requirement.
The official description connects treadmill training with Speed and biome exploration, but it publishes no biome names or thresholds. Use a repeatable one-minute treadmill measurement, confirm the rate with a second sample, then send that player-observed rate to the Speed goal calculator.
Write down the displayed speed before training so the sample has a clear starting point.
Train for a measured duration—one minute is convenient—without changing conditions you can control.
Subtract the starting speed from the ending speed and divide by the sample minutes.
Use a visible goal from your own progress. No site-supplied biome threshold is inserted.
Use the speed calculator, then take a fresh sample after a meaningful upgrade or update.
These stop conditions keep a useful estimate from turning into a claim the current game does not support.
The official description connects treadmill use to speed and biomes but does not publish one universal gain rate.
Use the requirement visible in-game; no ordered biome table was verified.
X2 Growth Speed says eggs grow faster. Only select 2× if your own treadmill sample shows it changes speed gain.
The official description links treadmill use to speed and reaching more biomes.
No official rate was verified; measure your current sample.
Biome names and thresholds were not verified.
The pass copy says eggs grow faster, so a treadmill effect is not assumed.
Choose another route after Treadmill, Speed and Biome Progression.
Open current-game references related to Treadmill, Speed and Biome Progression.
Turn your sample into an estimated time.
Read the exact X2 Growth Speed wording.
Place training inside the full game loop.