Income disclosure: We've been reader-supported and receive affiliate commissions if you purchase by means of hyperlinks on marathonhandbook.com. In case you are utilizing a heart price check to set your polarized training heart charge zones, you must observe these rules: Grant Holicky from Apex Coaching was interviewed and he talks https://gregoryuwtil.blogofoto.com/60888918/the-2-minute-rule-for-polarized-heart