Reply To: Drift Test vs Lactate Measurement? August 14, 2024 at 11:24 am #135722 SlowAndSteadyParticipant Too add, on my long runs (an hour and a half ish), once my heart rate gets to the 145-155 range 30-45 minutes in, I can usually keep my pace from then on without my heart rate continuing to increase at a steady rate