Building on our discussion of resting heart rate, let’s continue by looking at the positive changes to our bodies which come from effective training.
The “training effect” is a series of physiologic changes that occur in response to the efforts we produce. While the term was originally used to describe the positive adaptation caused by exercise, “training effect“ has now been morphed into a metric which measures the amount of improvement in several markers. We’ll stick to the old-school usage for this post.
In the resting heart rate piece, some of the physical changes to our heart (chamber size and improved contractility) were detailed. However, other changes also occur which allow our heart to pump more efficiently when under load.
The heart muscle itself is supplied with blood by the coronary arteries. Effective training causes the coronary arteries to dilate, allowing them to carry more blood to the heart muscle. This is crucial, as will be explained clearly by a look at how the heart muscle (and all muscles) gets blood supply.
During a heartbeat, the heart contracts and pumps blood from the left ventricle into the aorta through the aortic valve. As blood surges into the aorta, it stretches to accommodate the additional fluid volume. Since the heart (now much emptier) relaxes after squeezing the blood out, the blood from the pressurized aorta tries to turn around & seek the lowest pressure area (which is the empty,relaxed ventricle). As the blood rushes back toward the heart, the aortic valve closes & doesn’t allow the blood back into the heart. By miraculous design, the beginnings of the coronary arteries (“ostia”) are located just outside the heart on the other side of the aortic valve. So, when blood rushes back toward the heart and the aortic valve closes, some of the blood is diverted into the coronary arteries. The miracle continues, as this blood rushes into the heart muscle while it is relaxed! Blood does not flow well into ANY muscle while that muscle is contracted; the arteries & capillaries are too tightly compressed during the effort.
So, blood feeds our heart muscle IN BETWEEN beats. Now it makes sense why there is an upper limit “range” for maximum heart rate, as super-high rates don’t allow enough time for blood to flow into a relaxed muscle! This is why the coronary arteries “grow”, so they have a better chance of being able to carry enough blood to satisfy the heart’s demand.
Positive changes to coronary arteries is an important aspect of the “training effect”.
The rest of our muscles also get a blood-flow upgrade. Since our leg muscles beg for more food as well, the body adapts by enlarging those arteries & growing more extensive capillaries. The growth of new capillaries is called “angiogenesis”. Several of the big pro teams have their riders start their season by doing nothing but high-cadence/low-resistance pedaling for several weeks, which is thought to stimulate angiogenesis. Remember that blood doesn’t flow into muscles while they are contracting powerfully, so the light resistance/high cadence work helps to maximize the blood flow during this training phase.
Spin-ups are a short example of this. That’s why the coaches ask for “no higher than Zone 3 on spin-ups”! This effort level doesn’t contract the muscles so powerfully and prepares us for harder work by providing a chance for the leg muscles to optimize their blood flow. Although they don’t go into detail, there is a good reason for their coaching instructions! PZE rides are an integral part of this process!
Another effect of training, not surprisingly, is the upgrade to our lung function. After all, a tremendous amount of blood flow with limited oxygen aboard won’t work so well.😂. As I described in a post about breathing mechanics, the reminders we receive about our posture on the bike are aimed at allowing optimal breathing efficiency.
Our diaphragm becomes stronger and able to better draw fresh air into our lungs. The ability of our lungs to exchange oxygen & carbon dioxide increases, as the lining of our lungs becomes more permeable to gases. The measure of the lung’s ability to exchange gas is called the “coefficient of diffusion”. (No, there won’t be a quiz later😂).
So, better heart function and better lung function combined with muscles that have denser capillary supply are the result!
I hope this helps to explain a few things, and highlights the big benefits of PZ training.
This article is part of an ongoing series on Power Zone Training. You can find the other entries below in suggested reading order:
#1 – What is Power Zone Training?
#2 – FTP Test Strategies & Lessons
#3 – Power Zone Training – My Zones Are Too Easy!
#4 – Living with new zones & more FTP test
#5 – Post FTP-Test New Zone Struggles (Mental & Physical)
#6 – Decreases in FTP
#7 – Power Zone Training – My Zones Are Too Easy!
#8 – Age-related limitation & degradation of FTP in Power Zone Training
#9 – Resting Heart Rate: Why Power Zone Training reduces it
#10 – The “Training Effect” (This article)
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