By no means do I know diddly squat on heart rates, but I didn't think a high max heart rate on it's own is a bad thing? The rule of thumb for max HR is 220 minus your age...with 220 - 190 = 30...does that mean you have a heart of a 30 year old?
No. You are correct about the rule of thumb but just plugged the numbers in the wrong place. 220 - (age) say, 40 = estimated max heart rate of 180. That is just estimated. ( I think I understand what you are trying to say or show, but I don't think it works that way. ) There are several ways to find your exact max heart rate and none of them are fun if you are not a trained professional athlete. Here is one example: Let's use that same 40 year old with the estimated max of 180 bpm. We will use running as the stress exercise. You need to run for 20 minuets. Get your heart rate up to 90% of estimated max bpm in the first 10 minuets. (162 bpm) Keep it there for the next 10 minuets. In the last 10 minuets go as hard as you can for as long as you can (100% effort) If you give an honest 100% effort you will find your max heart rate in the last 10 minuets. You will notice it will climb fairly quickly then stop climbing and just wont beat any faster most likely 3 to 5 minuets into your last 10 minuet sprint. In my experience that is about the time your heart can't get rid of the acid in your muscles fast enough so most of your body will feel like it is on fire and you will feel like you are about to pass out or puke. That is when you know you gave 100% effort and found your true max heart rate.
In the data above, that max heart rate number is just the highest number his heart reached during that ride. In my experience when I ride or race my dirt bike it is much more enjoyable and much easier for me to reach my max heart rate than any other exercise. You are using so many muscles on the bike and having fun while doing it you may not even realize you maxed out your heart until you are gasping for air or wadded it up in a turn.
When I try to mimic my riding heart rate while doing any kind of cross training it damn near kills me. I can ride or race my dirt bike with in 1 or 2 % of my max heart rate for 15 to 20 minuets before I need to back it down for fear of an abrupt meeting with the deck. If I try to do that in the gym, road biking, or running I feel like I just want to stop and cry, or puke.
As far as I am concerned, MX is the best exercise I can get!