40 yrs old. Exercised for 30 minutes high intensity. Heart rate rose to 162. well within the 180 max range. 3 minutes post HR at 120....10 minutes post at 101....should it take that long to return to normal range of 60-100 bpm? At what point should I be concerned if it does not return to under 100 bpm? Isn't over 100 tachycardic?