Garmin Forerunner 255 Training Features

The Forerunner 255 occupies a unique position in Garmin's lineup: it has more training intelligence than the 165 but costs roughly the same on the used and discounted market. The key differentiator is Training Load tracking, which shows your cumulative training stress over 7 and 28 days and categorizes your overall status as Productive, Maintaining, Detraining, Overreaching, or Unproductive.

Training Load matters because it catches the mistake that ruins more training cycles than anything else: doing too much too fast. When you ramp weekly mileage by 30% because you feel good, Training Load flags the spike before your body breaks down. The Forerunner 165 cannot do this. For marathon and half-marathon trainers who follow periodized plans with deliberate load progression, this single feature justifies choosing the 255 over the 165.

HRV Status and Sleep Score both work as expected, giving you the overnight recovery picture that feeds into daily training decisions. Body Battery tracks energy throughout the day, and Recovery Time updates after each workout. The only missing piece is Training Readiness, which would combine all of these inputs into one morning score. Without it, you check HRV Status, Sleep Score, and Body Battery separately and connect the dots yourself.

The MIP display is the 255's biggest compromise. After seeing the AMOLED screens on the 165 and 265, the 255's screen looks washed out indoors. But MIP has a genuine advantage: sunlight readability is perfect, and battery life stretches to 14 days in smartwatch mode versus 5 on the 165. For runners who train outdoors and hate charging their watch every few days, the display trade-off is worth it.