Scientific consensus identifies two main factors that inevitably decline with age:
- your ability to utilize energy, and
- the resilience of your connective tissues to stretch and then spring back from the stretched position
In today’s article I’ll talk about the first of these two factors. You’ll have to wait for the next chapter to learn more about the second factor.
Your ability to utilize energy
There are plenty of ways to continue to improve your running efficiency – how much propulsion you can generate per unit of energy. But ultimately the incremental benefits you get from improved efficiency start to peter out, and your athletic improvement is limited by the sheer ability of your muscles to utilize energy to contract and release.
Many physiologic systems have to function in harmony in order for your muscles to utilize maximal energy:
- Your lungs take in more oxygen
- Your heart beats faster
- Each heart beat is stronger
- The arteries to your muscles dilate
- The metabolic systems within each muscle transform chemical energy into the mechanical force of contraction and release
It turns out that most of these physiologic systems can be strengthened or enhanced, even as you age. Except for one – the ability of your heart to beat faster.
Whatever your age, your heart will speed up in response to the chemical signals that activate the fight or flight reaction. But as you get older you can no longer push your heart beyond a certain maximal pumping rate.
You might be familiar with charts showing the maximal heart rate at different ages. The typical formula is that your maximal heart rate (in beats per minute) is equal to 220 minus your age. I’m 65. So as an example, my maximal heart rate should be 155. In my case, it seems that the standard chart is fairly accurate. I think I can get my heart rate into the low 160’s for brief periods of time But it’s really hard to do. And it’s really unpleasant.
Why can’t the older heart beat faster?
The heart has its own intrinsic rhythm system. Even without an outside signal, specialized heart cells generate an electric impulse that then spreads throughout the heart, initiating a beat.
Cellular impulse-generating systems, including those intrinsic to the heart, work by shifting calcium rapidly into and out of the cell. In order to do this, sophisticated protein complexes have evolved called “calcium channels.” The calcium channels span the space between the inner lining of the cell’s membrane and its outer lining. The calcium channel can twist, turn, open wide or shut tightly in response to a range of inputs, changing the rate of calcium flow.
These calcium channels (and other ion channels – sodium, for instance) are truly brilliant. They instantly change their configuration to respond to signals arising both inside and outside the cell, to changes in acidity, oxygen concentration, electric charge, and more.
As you age, the configuration of these proteins shifts and the channel gets more sluggish. It takes them longer to choreograph a cycle of calcium influx and outflow.
The aging of calcium channels doesn’t seem to respond to training. Nor has anyone figured out some other way to reverse these changes in the protein configuration of the channels.
And that is ultimately why your heart can’t beat as fast, and consequently you can’t run as fast.
Does the conventional wisdom fail to account for the truly brilliant nature of human adaptability?
It’s widely believed that the decline in maximal heart rate is an inevitable result of aging, and it can’t be improved with training. Given the widespread scientific acceptance of this idea, any further comment I make in that regard should best be viewed as wildly speculative.
That being said, over the past two years I’ve been studying functional medicine, which offers numerous diagnostic tests that look at the fundamental metabolic weak spots that underly chronic diseases; chronic conditions which, to greater or lesser degrees, are likewise considered to be the inevitable consequences of aging.
I recently encountered an interesting article published in The American Journal of Clinical Nutrition titled Nutrition and metal toxicity.
Lead is one of the toxic metals most commonly detected in the human body. Everybody’s got it in their system to some degree, and there is no “safe” level. Here’s a quote from the article’s abstract, which I’ve highlighted:
Lead competes with calcium, inhibiting the release of neurotransmitters, and interferes with the regulation of cell metabolism by binding to second-messenger calcium receptors, blocking calcium transport by calcium channels and calcium-sodium ATP pumps, and by competing for calcium-binding protein sites and uptake by mitochondria.
In other words, lead exposure (and probably exposure to other heavy metals) has a negative impact on calcium channel function and perhaps also on maximal heart rate.
How do I get my heavy metals tested? And what do I do if the levels are high?
Lead and other heavy metals have a negative effect on many body processes, not just on maximal heart rate. So even if you’re not training for a half marathon, you may want to have your lead levels tested.
I offer a lead test as part of a more comprehensive measure of the levels of a range of metals: helpful minerals that are part of the ordinary diet as well as the toxic heavy metals.
If you test high for toxic metals, I can design a detox program for you that strengthens the specific metabolic pathways that have to kick into gear to process the specific toxins you’ve been exposed to.