As I have read in other reviews during the first outings, heart values were totally aberrant (highly elevated). Everything is back to normal after four or five outings. Even early in the race, cardio hump correctly. Before contacting amazon sav, I persevere after reading the many comments from users on the site. Thank you to them. I bought this product to replace mine that showed incorrect values (after 3 years), especially early in the race (20 minutes). Bravo amazon for their shipments fast and always without problems.