LIKE NEW (used for 1 month) Included: original box, new charging cord and new strap Here’s how it works: When you join, your age is plugged into an industry-standard formula to estimate your MaxHR. After taking 5 eligible classes in 120 days, our custom OTF algorithm adjusts your MaxHR to more accurately reflect your in-studio performance. From there, your MaxHR will automatically adjust as needed with every class you take under the orange lights.