There’s been some buzz all over polarized bicycle interval training in cycling following the Velonews podcast, Rapidly Communicate, hosted 2 interviews with Dr. If all of the chambers contracted concurrently, then blood couldn't circulation in the heart because the AV valves would reduce blood stream between the atria and ventricles. https://live-mistress-cam81467.designertoblog.com/61130320/the-ultimate-guide-to-polarized-heart