My Max HR declines the more I exercise

Question

I am 49 years old and have been doing endurance type sports since age 6 and started tracking my HR on the popular devices since 2004, attending every major training coarse I can and reading a few books how to calculate (Max HR - (Resting x 80%) + Resting) = 80% Max HR, etc.

The challenge I have is that my Max HR has never exceeded 155 and the more I train the lower it goes. I recently have to really push extremely hard on a cycle race of 3-4 Hours and if I push excessively high on a 5-7% gradient can get my HR up to 144, but it hurts really bad and at that point I cannot breath and definitely wont not be able to talk.

When doing non-frequent exercises (in my case running or weight training) my Hr go up very quickly, but max out at the same level, when I run out of breath and feels like I am going to die from oxygen starvation.

When doing an ECG (treadmill) the feedback is that my hart is very big as a result of my sporting history and being active since age 6.

I recently spoke to someone during a training ride who mentioned that he had the same problem and through medication had it resolved. This gave me new hope, as I still think it is VO2 related and not the actual Max HR itself.

I used to be an very explosive cycling sprinter in my young days, but the low range between a moderate level ride @ HR 105 to a serious sprint @ HR140 is just not enough to keep up the tempo for the final 2-3 kilometers.

Answer 1

There's a lot of quality peer reviewed data out there showing links between aerobic exercise and your heart, but a good summary (with cited studies) is this article from Johns Hopkins:

[Exercise] improves the muscles’ ability to pull oxygen out of the blood, reducing the need for the heart to pump more blood to the muscles.

Distance cyclists and long term runners can even develop Athlete's Heart (AHS), which is basically a bigger volume heart with more powerful valving and muscle strength. Your heart, like every other muscle, adapts to the load and performs it more efficiently.

Not only can your heart pump more blood per stroke (decreasing your heart rate), but your skeletal muscles (quads, hamstrings, biceps, etc) become better at their power production and your technique requires less power. All over you simply become more efficient.

One part of us that doesn't tend to change much though is the pulmonary system:

Endurance training induces large and significant adaptations within the cardiovascular, musculoskeletal and haematological systems. However, the structural and functional properties of the lung and airways do not change in response to repetitive physical activity and, in elite athletes, the pulmonary system may become a limiting factor to exercise at sea level and altitude.

Miguel Indurain had a resting heart rate of 28, but like most high level endurance athletes he had an incredibly high VO2 max of 88 with a normal college athlete in the 50 range.

I would get your VO2 max checked out and your power production. Your heart rate is really akin to the RPM's on your car: it's good to know and too much or too low is a warning sign, but it can't be looked at independently of other items like transmission, fuel flow, fuel/air mixture, etc.

Likewise your heart's job is just to push oxygen perfused blood around and take the spent stuff to the lungs, and back again. Your blood oxygen, calcium uptake, and a host of other factors are probably what to examine first. Especially considering that in a well trained athlete, your heart rate should be dropping over the years (to a point) as it's getting better and better at its job.

Start with VO2 max and power, and go from there.