The ranges are given for the RESTING HR. This is a physical and emotional state...so one has to consider their physical and emotional state when they measure their HR and compare it with the "normal" ranges.
For a health young heart (say under 45 years old) a resting HR of 120 while technically techycardia is not normally considered dangerous, unhealthy, possibly, but not dangerous. The same HR at over 200 that last more than a few minutes and is unexplained would be well advised to visit the hospital emergency room.
Similarly for Bradycardia. Some people do fine with a resting HR as low as 40. Lower, I'd seek medical help regardless of how well I felt otherwise.
Also, if you are a woman your heart rate is typically at the higher end of the range unless genetics plays a role.
Hello Mattie-
The basic rule of thumb is...
Less than 60 beats per minute = a slower heart rate (ie, bradycardia)
60-99 beats per minute = normal
100+ beats/min = a faster heart rate (tachycardia)
Hope that helps a little.
Marell