Dr. Seiler Answers Five Great Endurance Questions Dr. Stephen Seiler answers five endurance training questions on heart rate, zones, polarized training, rest, and much more. Dr. Stephen Seiler Mar 1st 2021 Dr. Stephen Seiler answers five endurance training questions on heart rate, zones, polarized training, rest, and much more. This content is for Library, Listener, and Forum members only.Listener Membership is FREE. Please join now.Log In Join Now