Training & Nutrition - New max heart rate...?

I've been putting in some good miles this summer and losing a bit a weight...and getting faster on the bike. I'm 44, 185lbs. My previous highest recorded heart rate was 182 but yesterday I hit 189 in a sprint in a friendly crit. Pretty well max effort. Does it make sense that I can reach this heart rate or it there likely something wrong with my heart rate monitor. I time trial at about 172bpm for 25 minutes. Would this be 85%? Would it make sense to use that as 85% and adjust my heart rate zones accordingly? Or is it reasonable to be able to ride at say +90% for 25 minutes? A year ago max hit was 170, then 174, then 178, then 182 now 189. This is all good, right? Any comments greatly appreciated. Thanks.

It's impossible to tell if 172 is 85% because that time trial HR can vary considerably but if that's where you feel comfortable TT'ing then that's the HR you should build your training around.

Your HRmax is not actually increasing. What is happening is that you are getting better at riding at high exertion levels long enough for your heartrate to approach your HRmax. HRmax does not increase with training and a high HRmax is not an indication of fitness.

Generally, it is very difficult to achieve your HRmax. You usually need to be very motivated to do so and structure a workout specifically to do it.

Different people have different-sized hearts, so max heart rate is a personal thing for a specific sport. 189 is a bit high for somebody your age, but isn't unusual. I hit about 171-173 at 42 years old, but my heart is a bit larger than average - my resting is in the low 40s and hit the high 30s in mid-summer.

It's not clear to me what you're asking about 85% or 90%. It is possible to ride 90% for 10-15 minutes if you are trained for it.

I'm 41 and get up to 197... Individual max HR varies quite a lot. The best you can do is simply go by the highest number you've recorded, which will probably slowly increase towards your personal physical limit over time.

I'm 40 and have hit 204 on a number of times and I have been told by more than one Dr. that I have a larger than normal heart so I'm not so sure the size of your heart has any impact on your Max HR.

im 15 and have hit 208 on one ocassion, is that normal, it seems awfully high