I had my HRM for a few months now. My max Hr went from 170 to 171 now it's 173 in the last few months. Is this normal? Your max heart rate changing

I'm not an HRM expert but have used one off and on for a few years now, and each one is a little different. It might help others help you if you say what HRM that you are using. All I can suggest is that if your physical conditioning is improving it might be affecting what the HRM reports.

How do you know it's really your max? That is to say, are you sure you really hit your true max on the earlier rides, or on the last one for that matter.

Is that the max you've ever seen? Is that what some calculator told you? Age/weight/fitness makes a huge difference. Your "max" won't necessarily change, but you should see your HR come down for the same effort over time. With that said, you could be more fit and more willing to push harder, which would result in you seeing higher numbers overall.

It could go up because of a million variables - Heat, wind, salt, dehydration, lack of sleep (or anything that increases adrenaline or cortisol). 3 bpm over 170 is very small. When I'm pushing threshold on intervals I'm regularly up in the 170-180 range, sometimes higher. This is fine, and for while working out is perfectly healthy, assuming you are generally healthy enough to handle this strain. The max I've ever registered was 210 when I absolutely exploded trying to chase down the paceline on a fast group ride when I was spit out the back. That was not fun at all. 170 is normal for a good effort depending on your age and conditioning.

Anything above zero is good.

mine varies based on temperature. no big deal.

or it could mean you're dying.

Yes, a changing max HR is normal. They go up and down depending on training state. The only thing to worry about is if the highest HR you can manage drops significantly. That usually means you're overdoing it and need to back it off for a few days.

When I started back riding my MaxHR on the bike was quite a bit lower than my running MaxHR. Over time my max on the bike caught up with my running max.

Yes. It's so normal that Garmin computers have an "auto-detect" option for MaxHR.

What do you really mean by max? Is it the highest heart rate you can achieve at your current fitness level? The most your body will ever be able to achieve? What you're up to today, after staying up too late and making up for it with lots of coffee? It's a slightly fuzzy concept, which leads to slightly different answers if you measure on different days. Keep in mind 170 vs 173 is within 2 %, the margin of error is bigger than that for optical HRMs.

It's hard to hit my running MinHR on the bike!

I would take the max to mean the highest heart rate you can achieve at your current fitness level. I wonder whether the OP's max increased or whether he or she pushed to slightly higher values (possibly not maximal) on the three occasions mentioned. It's really hard to push yourself to your true max.

The max is what the Garmin was showing. I think I got the HRM in Dec or Nov. And those two months was when I felt over trained. I have low my miles from 160miles on the weekends to about 90 miles. And I was doing a lot of intervals too. I have but some weight back on, I'm about up to 175ish pounds now. I did hit 174 last Saturday on the HRM. In my first post I was just wondering if this was common?Thanks everyone

Your max heart rate is basically fixed and decreases slowly as you age. It's independent of fitness level. It's not what you hit in hard effort, but the max you can ever hit. It's extremely difficult to hit your max rate and can only be done for very short periods of time, much less than a minute, and only at excruciating exertion levels.