The Circadian Rhythm: Far More Than Most People Know
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The Circadian Rhythm: Far More Than Most People Know
This is Dr. Satchidananda (Satchin) Panda, the scientist behind the discovery of the blue-light sensing cell type in the retina, and the many things it affects. But, he’s discovered more…
First, what you probably know (with a little more science)
Dr. Panda discovered that melanopsin, a photopigment, is “the primary candidate for photoreceptor-mediated entrainment”.
To put that in lay terms, it’s the brain’s go-to for knowing approximately what time of day or night it is, according to how much light there is (or isn’t), and how long it has (or hasn’t) been there.
But… the brain’s “go-to” isn’t the only method. By creating mice without melanopsin, he was able to find that they still keep a circadian rhythm, even in complete darkness:
Melanopsin (Opn4) Requirement for Normal Light-Induced Circadian Phase Shifting
In other words, it was a helpful, but not completely necessary, means of keeping a circadian rhythm.
So… What else is going on?
Dr. Panda and his team did a lot of science that is well beyond the scope of this main feature, but to give you an idea:
- With jargon: it explored the mechanisms and transcription translation negative feedback loops that regulate chronobiological processes, such as a histone lysine demathlyase 1a (JARID1a) that enhances Clock-Bmal1 transcription, and then used assorted genomic techniques to develop a model for how JARID1a works to moderate the level of Per transcription by regulating the transition between its repression and activation, and discovered that this heavily centered on hepatic gluconeogenesis and glucose homeostasis, facilitated by the protein cryptochrome regulating the fasting signal that occurs when glucagon binds to a G-protein coupled receptor, triggering CREB activation.
- Without jargon: a special protein tells our body how to respond to eating/fasting at different times of day—and conversely, certain physiological responses triggered by eating/fasting help us know what time of day it is.
- Simplest: our body keeps on its best cycle if we eat at the same time every day
This is important, because our circadian rhythm matters for a lot more than sleeping/waking! Take hormones, for example:
- Obvious hormones: testosterone and estrogen peak in the mornings around 9am, progesterone peaks between 10pm and 2am
- Forgotten hormones: cortisol peaks in the morning around 8:30am, melatonin peaks between 10pm and 2am
- More hormones: ghrelin (hunger hormone) peaks around 10am, leptin (satiety hormone) peaks 20 minutes after eating a certain amount of satiety-triggering food (protein does this most quickly), insulin is heavily tied to carbohydrate intake, but will still peak and trough according to when the body expects food.
What does this mean for us in practical terms?
For a start, it means that intermittent fasting can help guard against metabolic and related diseases (including inflammation, and thus also cancer, diabetes, arthritis, and more) a lot more if we practice it with our circadian rhythm in mind.
So that “8-hour window” for eating, that many intermittent fasting practitioners adhere to, is going to do much, much better if it’s 10am to 6pm, rather than, say, 4pm to midnight.
Additionally, Dr. Panda and his team found that a 12-hour eating window wasn’t sufficient to help significantly.
Some other take-aways:
- For reasons beyond the scope of this article, it’s good to exercise a) early b) before eating, so getting in some exercise between 8.30am and 10am is ideal
- It also means it’s beneficial to “front-load” eating, so a large breakfast at 10am, and smaller meals/snacks afterwards, is best.
- It also means that getting sunlight (even if cloud-covered) around 8.30am helps guard against metabolic disorders a lot, since the light remains the body’s go-to way of knowing the time.
- We realize that sunlight is not available at 8.30am at all latitudes at all times of year. Artificial is next-best.
- It also means sexual desire will typically peak in men in the mornings (per testosterone) and women in the evenings (per progesterone), but this is just an interesting bit of trivia, and not so relevant to metabolic health
What to do next…
Want to stabilize your own circadian rhythm in the best way, and also help Dr. Panda with his research?
His team’s (free!) app, “My Circadian Clock”, can help you track and organize all of the body’s measurable-by-you circadian events, and, if you give permission, will contribute to what will be the largest-yet human study into the topics covered today, to refine the conclusions and learn more about what works best.
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Can You Be Fat AND Fit?
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The short answer is “yes“.
And as for what that means for your heart and/or all-cause mortality risk: it’s just as good as being fit at a smaller size, and furthermore, it’s better than being less fit at a smaller size.
Here’s the longer answer:
The science
A research team did a systematic review looking at multiple large cohort studies examining the associations between:
- Cardiorespiratory fitness and cardiovascular disease risk
- Cardiorespiratory fitness and all-cause mortality
- BMI and cardiovascular disease risk
- BMI and all-cause mortality
However, they also took this further, and tabulated the data such that they could also establish the cardiovascular disease mortality risk and all-cause mortality risk of:
- Unfit people with “normal” BMI
- Unfit people with “overweight” BMI
- Unfit people with “obese” BMI
- Fit people with “normal” BMI
- Fit people with “overweight” BMI
- Fit people with “obese” BMI
Before we move on, let’s note for the record that BMI is a woeful system in any case, for enough reasons to fill a whole article:
Now, with that in mind, let’s get to the results:
What they found
For cardiovascular disease mortality risk of unfit people specifically, compared to fit people of “normal” BMI:
- Unfit people with “normal” BMI: 2.04x higher risk.
- Unfit people with “overweight” BMI: 2.58x higher risk.
- Unfit people with “obese” BMI: 3.35x higher risk
So here we can see that if you are unfit, then being heavier will indeed increase your CVD mortality risk.
For all-cause mortality risk of unfit people specifically, compared to fit people of “normal” BMI:
- Unfit people with “normal” BMI: 1.92x higher risk.
- Unfit people with “overweight” BMI: 1.82x higher risk.
- Unfit people with “obese” BMI: 2.04x higher risk
This time we see that if you are unfit, then being heavier or lighter than “overweight” will increase your all-cause mortality risk.
So, what about if you are fit? Then being heavier or lighter made no significant difference to either CVD mortality risk or all-cause mortality risk.
Fit individuals, regardless of weight category (normal, overweight, or obese), had significantly lower mortality risks compared to unfit individuals in any weight category.
Note: not just “compared to unfit individuals in their weight category”, but compared to unfit individuals in any weight category.
In other words, if you are obese and have good cardiorespiratory fitness, you will (on average) live longer than an unfit person with “normal” BMI.
You can find the paper itself here, if you want to examine the data and/or method:
Cardiorespiratory fitness, body mass index and mortality: a systematic review and meta-analysis
Ok, so how do I improve the kind of fitness that they measured?
They based their cardiorespiratory fitness on VO2 Max, which scientific consensus holds to be a good measure of how efficiently your body can use oxygen—thus depending on your heart and lungs being healthy.
If you use a fitness tracker that tracks your exercise and your heart rate, it will estimate your VO2 Max for you—to truly measure the VO2 Max itself directly, you’ll need a lot more equipment; basically, access to a lab that tests this. But the estimates are fairly accurate, and so good enough for most personal purposes that aren’t hard-science research.
Next, you’ll want to do this:
53 Studies Later: The Best Way to Improve VO2 Max
Take care!
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What Does “Balance Your Hormones” Even Mean?
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Hormonal Health: Is It Really A Balancing Act?
Have you ever wondered what “balancing your hormones” actually means?
The popular view is that men’s hormones look like this:
Testosterone (less) ⟷ Testosterone (more)
…And that women’s hormones look more like this:
♀︎ Estrogen ↭ Progesterone ⤵︎
⇣⤷ FSH ⤦ ↴ ☾ ⤹⤷ Luteinizing Hormone ⤦
DHEA ↪︎ Gonadotrophin ⤾
↪︎ Testosterone? ⥅⛢
Clear as mud, right?
But, don’t worry, Supplements McHerbal Inc will sell you something guaranteed to balance your hormones!
How can a supplement (or dietary adjustment) “balance” all that hotly dynamic chaos, and make everything “balanced”?
The truth is, “balanced” in such a nebulous term, and this is why you will not hear endocrinologists using it. It’s used in advertising to mean “in good order”, and “not causing problems”, and “healthy”.
In reality, our hormone levels depend on everything from our diet to our age to our anatomy to our mood to the time of the day to the phase of the moon.
Not that the moon has an influence on our physiology at all—that’s a myth—but you know, 28 day cycle and all. And, yes, half the hormones affect the levels of the others, either directly or indirectly.
Trying to “balance” them would be quite a game of whack-a-mole, and not something that a “cure-all” single “hormone-balancing” supplement could do.
So why aren’t we running this piece on Friday, for our “mythbusting” section? Well, we could have, but the more useful information is yet to come and will take up more of today’s newsletter than the myth-busting!
What, then, can we do to untangle the confusion of these hormones?
Well first, let’s understand what they do, in the most simple terms possible:
- Estrogen—the most general feminizing hormone from puberty onwards, busiest in the beginning of the menstrual cycle, and starts getting things ready for ovulation.
- Progesterone—secondary feminizing hormone, fluffs the pillows for the oncoming fertilized egg to be implanted, increases sex drive, and adjusts metabolism accordingly. Busiest in the second half of the menstrual cycle.
- Testosterone—is also present, contributes to sex drive, is often higher in individuals with PCOS. If menopause is untreated, testosterone will also rise, because there will be less estrogen
- (testosterone and estrogen “antagonize” each other, which is the colorfully scientific way of saying they work against each other)
- DHEA—Dehydroepiandrosterone, supports production of testosterone (and estrogen!). Sounds self-balancing, but in practice, too much DHEA can thus cause elevated testosterone levels, and thus hirsutism.
- Gonadotrophin—or more specifically human chorionic gonadotrophin, HcG, is “the pregnancy hormone“, present only during pregnancy, and has specific duties relating to such. This is what’s detected in (most) pregnancy test kits.
- FSH—follicle stimulating hormone, is critical to ovulation, and is thus essential to female fertility. On the other hand, when the ovaries stop working, FSH levels will rise in a vain attempt to encourage the ovulation that isn’t going to happen anymore.
- Luteinizing hormone—says “go” to the new egg and sends it on its merry way to go get fertilized. This is what’s detected by ovulation prediction kits.
Sooooooo…
What, for most women, most often is meant by a “hormonal imbalance” is:
- Low levels of E and/or P
- High levels of DHEA and/or T
- Low or High levels of FSH
In the case of low levels of E and/or P, the most reliable way to increase these is, drumroll please… To take E and/or P. That’s it, that’s the magic bullet.
Bonus Tip: take your E in the morning (this is when your body will normally make more and use more) take your P in the evening (it won’t make you sleepy, but it will improve your sleep quality when you do sleep)
In the case of high levels of DHEA and/or T, then that’s a bit more complex:
- Taking E will antagonize (counteract) the unwanted T.
- Taking T-blockers (such as spironolactone or bicalutamide) will do what it says on the tin, and block T from doing the jobs it’s trying to do, but the side-effects are considered sufficient to not prescribe them to most people.
- Taking spearmint or saw palmetto will lower testosterone’s effects
- Scientists aren’t sure how or why spearmint works for this
- Saw palmetto blocks testosterone’s conversion into a more potent form, DHT, and so “detoothes” it a bit. It works similarly to drugs such as finasteride, often prescribed for androgenic alopecia, called “male pattern baldness”, but it affects plenty of women too.
In the case of low levels of FSH, eating leafy greens will help.
In the case of high levels of FSH, see a doctor. HRT (Hormone Replacement Therapy) may help. If you’re not of menopausal age, it could be a sign something else is amiss, so it could be worth getting that checked out too.
What can I eat to boost my estrogen levels naturally?
A common question. The simple answer is:
- Flaxseeds and soy contain plant estrogens that the body can’t actually use as such (too incompatible). They’ve lots of high-quality nutrients though, and the polyphenols and isoflavones can help with some of the same jobs when it comes to sexual health.
- Fruit, especially peaches, apricots, blueberries, and strawberries, contain a lot of lignans and also won’t increase your E levels as such, but will support the same functions and reduce your breast cancer risk.
- Nuts, especially almonds (yay!), cashews, and pistachios, contain plant estrogens that again can’t be used as bioidentical estrogen (like you’d get from your ovaries or the pharmacy) but do support heart health.
- Leafy greens and cruciferous vegetables support a lot of bodily functions including good hormonal health generally, in ways that are beyond the scope of this article, but in short: do eat your greens!
Note: because none of these plant-estrogens or otherwise estrogenic nutrients can actually do the job of estradiol (the main form of estrogen in your body), this is why they’re still perfectly healthy for men to eat too, and—contrary to popular “soy boy” social myths—won’t have any feminizing effects whatsoever.
On the contrary, most of the same foods support good testosterone-related health in men.
The bottom line:
- Our hormones are very special, and cannot be replaced with any amount of herbs or foods.
- We can support our body’s natural hormonal functions with good diet, though.
- Our hormones naturally fluctuate, and are broadly self-correcting.
- If something gets seriously out of whack, you need an endocrinologist, not a homeopath or even a dietician.
In case you missed it…
We gave a more general overview of supporting hormonal health (including some hormones that aren’t sex hormones but are really important too), back in February.
Check it out here: Healthy Hormones And How To Hack Them
Want to read more?
Anthea Levi, RD, takes much the same view:
❝For some ‘hormone-balancing’ products, the greatest risk might simply be lost dollars. Others could come at a higher cost.❞
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CBD Oil’s Many Benefits
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CBD Oil: What Does The Science Say?
First, a quick legal (and practical) note:
CBD and THC are both derived from the hemp or cannabis plant, but only the latter has euphoriant psychoactive effects, i.e., will get you high. We’re writing here about CBD derived from hemp and not containing THC (thus, will not get you high).
Laws and regulations differ far too much from place to place for us to try to advise here, so please check your own local laws and regulations. And also, while you’re at it, with your doctor and/or pharmacist.
As ever, this newsletter is for purposes of education and enjoyment, and does not constitute any kind of legal (or medical) advice.
With that in mind, onwards to today’s research review…
CBD for Pain Relief
CBD has been popularly touted as a pain relief panacea, and there are a lot of pop-science articles out there “debunking” this, but…
The science seems to back it up. We couldn’t find studies refuting the claim (of CBD as a viable pain relief option). We did, however, find research showing it was good against:
Note that that latter (itself a research review, not a single study, hence covering a lot of bases) describes it matter-of-factly, with no caveats or weasel-words, as:
“CBD, a non-euphoriant, anti-inflammatory analgesic with CB1 receptor antagonist and endocannabinoid modulating effects”
As a quick note: all of the above is about the topical use of CBD oil, not any kind of ingestion
CBD for Anxiety/Depression
There’s a well-cited study with what honestly we think was a bit of a small sample size, but compelling results within that:
A study published in the Brazilian Journal of Psychiatry tested the anxiety levels of 57 men in a simulated public speaking test.
Compared to placebo…
- Those who received 300mg of CBD experienced significantly reduced anxiety during the test.
- Those who received either 150mg or 600mg of CBD experienced more anxiety during the test than the 300mg group
- This means there’s a sweet spot to the dosage
There was also a clinical study that found CBD to have anti-depressant effects.
The methodology was a lot more robust, but the subjects were mice. We can’t have everything in one study, apparently! There is probably a paucity of human volunteers to have their brain slices looked at after tests, though.
Anyway, what makes this study interesting is that it measured quite an assortment of biological markers in the brain, and found that the CBD had a similar physiological effect to the antidepressant imipramine.
CBD for Treating Opioid Addiction
There are a lot of studies for this, both animal and human, but we’d like to put the spotlight on a human study (with the participation of heroin users) that found:
❝Within one week, CBD significantly reduced cravings, anxiety, resting heart rate, and salivary cortisol levels. No serious adverse effects were found.❞
This is groundbreaking because the very thing about heroin is that it’s so addictive and the body rapidly needs more and more of it. You might think “duh”, but most people don’t realize this part:
Heroin is attractive because it offers (and delivers) an immediate guaranteed “downer”, instant relaxation… with none of the bad side effects of, for example, alcohol. No nausea, no hangover, nothing.
The problem is that the body gets tolerant to heroin very quickly, meaning your doses need to get bigger and more frequent to have the same effect.
Before you know it, what seemed like an affordable “self-medication for a stressful life” is very much out of control! Many doctors have personally found this out the hard way.
So, it’s ruinous:
- first to your financial health, as the costs rapidly spiral
- then to your physical health, as you either suffer from withdrawal or eventually overdose
Consequently, heroin is an incredibly easy drug to get hooked onto, and incredibly difficult to get back off.
So CBD offering relief is really a game-changer.
And more…
CBD has been well-studied and found to be effective for a lot of things, more than we could hope to cover in a single edition here.
Some further reading that may interest you includes:
- CBD against Diabetes in mice / in vitro / in humans
- CBD against neurological diseases (in general, in humans)
- CBD against arthritis in mice / in humans
- CBD specifically against the pain of rheumatoid arthritis / of osteoarthritis
Let us know if there’s any of these (or other) conditions you’d like us to look more into the CBD-related research for, because there’s a lot! You can always hit reply to any of our emails, or use the feedback widget at the bottom
Read (and shop, if you want and it’s permitted where you are):
10 Best CBD Oils of 2023, According to the Forbes Health Advisory Board
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Cupping: How It Works (And How It Doesn’t)
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Good Health By The Cup?
In Tuesday’s newsletter, we asked you for your opinion of cupping (the medical practice), and got the above-depicted, below-described, set of responses:
- About 40% said “It may help by improving circulation and stimulating the immune system”
- About 26% said “I have never heard of the medical practice of cupping before this”
- About 19% said “It is pseudoscience and/or placebo at best, but probably not harmful
- About 9% said “It is a good, evidence-based practice that removes toxins and stimulates health”
- About 6% said “It is a dangerous practice that often causes harm to people who need medical help”
So what does the science say?
First, a quick note for those unfamiliar with cupping: it is the practice of placing a warmed cup on the skin (open side of the cup against the skin). As the warm air inside cools, it reduces the interior air pressure, which means the cup is now (quite literally) a suction cup. This pulls the skin up into the cup a little. The end result is visually, and physiologically, the same process as what happens if someone places the nozzle of a vacuum cleaner against their skin. For that matter, there are alternative versions that simply use a pump-based suction system, instead of heated cups—but the heated cups are most traditional and seem to be most popular. See also:
National Center for Complementary and Integrative Health | Cupping
It is a dangerous practice that often causes harm to people who need medical help: True or False?
False, for any practical purposes.
- Directly, it can (and usually does) cause minor superficial harm, much like many medical treatments, wherein the benefits are considered to outweigh the harm, justifying the treatment. In the case of cupping, the minor harm is usually a little bruising, but there are other risks; see the link we gave just above.
- Indirectly, it could cause harm by emboldening a person to neglect a more impactful treatment for their ailment.
But, there’s nothing for cupping akin to the “the most common cause of death is when someone gets a vertebral artery fatally severed” of chiropractic, for example.
It is a good, evidence-based practice that removes toxins and stimulates health: True or False?
True and False in different parts. This one’s on us; we included four claims in one short line. But let’s look at them individually:
- Is it good? Well, those who like it, like it. It legitimately has some mild health benefits, and its potential for harm is quite small. We’d call this a modest good, but good nonetheless.
- Is it evidence-based? Somewhat, albeit weakly; there are some papers supporting its modest health claims, although the research is mostly only published in journals of alternative medicine, and any we found were in journals that have been described by scientists as pseudoscientific.
- Does it remove toxins? Not directly, at least. There is also a version that involves making a small hole in the skin before applying the cup, the better to draw out the toxins (called “wet cupping”). This might seem a little medieval, but this is because it is from early medieval times (wet cupping’s first recorded use being in the early 7th century). However, the body’s response to being poked, pierced, sucked, etc is to produce antibodies, and they will do their best to remove toxins. So, indirectly, there’s an argument.
- Does it stimulate health? Yes! We’ll come to that shortly. But first…
It is pseudoscience and/or placebo at best, but probably not harmful: True or False?
True in that its traditionally-proposed mechanism of action is a pseudoscience and placebo almost certainly plays a strong part, and also in that it’s generally not harmful.
On it being a pseudoscience: we’ve talked about this before, but it bears repeating; just because something’s proposed mechanism of action is pseudoscience, doesn’t necessarily mean it doesn’t work by some other mechanism of action. If you tell a small child that “eating the rainbow” will improve their health, and they believe this is some sort of magical rainbow power imbuing them with health, then the mechanism of action that they believe in is a pseudoscience, but eating a variety of colorful fruit and vegetables will still be healthy.
In the case of cupping, its proposed mechanism of action has to do withbalancing qi, yin and yang, etc (for which scientific evidence does not exist), in combination with acupuncture lore (for which some limited weak scientific evidence exists). On balancing qi, yin and yang etc, this is a lot like Europe’s historically popular humorism, which was based on the idea of balancing the four humors (blood, yellow bile, black bile, phlegm). Needless to say, humorism was not only a pseudoscience, but also eventually actively disproved with the advent of germ theory and modern medicine. Cupping therapy is not more scientifically based than humorism.
On the placebo side of things, there probably is a little more to it than that; much like with acupuncture, a lot of it may be a combination of placebo and using counter-irritation, a nerve-tricking method to use pain to reduce pain (much like pressing with one’s nail next to an insect bite).
Here’s one of the few studies we found that’s in what looks, at a glance, to be a reputable journal:
Cupping therapy and chronic back pain: systematic review and meta-analysis
It may help by improving circulation and stimulating the immune system: True or False?
True! It will improve local circulation by forcing blood into the area, and stimulate the immune system by giving it a perceived threat to fight.
Again, this can be achieved by many other means; acupuncture (or just “dry needling”, which is similar but without the traditional lore), a cold shower, and/or exercise (and for that matter, sex—which combines exercise, physiological arousal, and usually also foreign bodies to respond to) are all options that can improve circulation and stimulate the immune system.
You can read more about using some of these sorts of tricks for improving health in very well-evidenced, robustly scientific ways here:
The Stress Prescription (Against Aging!)
Take care!
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Hazelnuts vs Chestnuts – Which is Healthier?
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Our Verdict
When comparing hazelnuts to chestnuts, we picked the hazelnuts.
Why?
This one’s not close.
In terms of macros, we have some big difference to start with, since chestnuts contain a lot more water and carbs whereas hazelnuts contain a lot more protein, fats, and fiber. The fats, as with most nuts, are healthy; in this case mostly being monounsaturated fat.
Because of the carbs and fiber being so polarized (i.e., chestnuts have most of the carbs and hazelnuts have most of the fiber), there’s a big difference in glycemic index; hazelnuts have a GI of 15 while chestnuts have a GI of 52.
In the category of vitamins, hazelnuts contain more of vitamins A, B1, B2, B3, B5, B6, and B9, while chestnuts contain more vitamin C.
When it comes to minerals, the story is similar: hazelnuts contain a lot more calcium, copper, iron, magnesium, manganese, phosphorus, and zinc, while chestnuts contain a tiny bit more potassium.
All in all, enjoy either or both, but nutritionally speaking, hazelnuts are a lot better in almost every way.
Want to learn more?
You might like to read:
Why You Should Diversify Your Nuts
Take care!
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What are heart rate zones, and how can you incorporate them into your exercise routine?
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If you spend a lot of time exploring fitness content online, you might have come across the concept of heart rate zones. Heart rate zone training has become more popular in recent years partly because of the boom in wearable technology which, among other functions, allows people to easily track their heart rates.
Heart rate zones reflect different levels of intensity during aerobic exercise. They’re most often based on a percentage of your maximum heart rate, which is the highest number of beats your heart can achieve per minute.
But what are the different heart rate zones, and how can you use these zones to optimise your workout?
The three-zone model
While there are several models used to describe heart rate zones, the most common model in the scientific literature is the three-zone model, where the zones may be categorised as follows:
- zone 1: 55%–82% of maximum heart rate
- zone 2: 82%–87% of maximum heart rate
- zone 3: 87%–97% of maximum heart rate.
If you’re not sure what your maximum heart rate is, it can be calculated using this equation: 208 – (0.7 × age in years). For example, I’m 32 years old. 208 – (0.7 x 32) = 185.6, so my predicted maximum heart rate is around 186 beats per minute.
There are also other models used to describe heart rate zones, such as the five-zone model (as its name implies, this one has five distinct zones). These models largely describe the same thing and can mostly be used interchangeably.
What do the different zones involve?
The three zones are based around a person’s lactate threshold, which describes the point at which exercise intensity moves from being predominantly aerobic, to predominantly anaerobic.
Aerobic exercise uses oxygen to help our muscles keep going, ensuring we can continue for a long time without fatiguing. Anaerobic exercise, however, uses stored energy to fuel exercise. Anaerobic exercise also accrues metabolic byproducts (such as lactate) that increase fatigue, meaning we can only produce energy anaerobically for a short time.
On average your lactate threshold tends to sit around 85% of your maximum heart rate, although this varies from person to person, and can be higher in athletes.
Wearable technology has taken off in recent years. Ketut Subiyanto/Pexels In the three-zone model, each zone loosely describes one of three types of training.
Zone 1 represents high-volume, low-intensity exercise, usually performed for long periods and at an easy pace, well below lactate threshold. Examples include jogging or cycling at a gentle pace.
Zone 2 is threshold training, also known as tempo training, a moderate intensity training method performed for moderate durations, at (or around) lactate threshold. This could be running, rowing or cycling at a speed where it’s difficult to speak full sentences.
Zone 3 mostly describes methods of high-intensity interval training, which are performed for shorter durations and at intensities above lactate threshold. For example, any circuit style workout that has you exercising hard for 30 seconds then resting for 30 seconds would be zone 3.
Striking a balance
To maximise endurance performance, you need to strike a balance between doing enough training to elicit positive changes, while avoiding over-training, injury and burnout.
While zone 3 is thought to produce the largest improvements in maximal oxygen uptake – one of the best predictors of endurance performance and overall health – it’s also the most tiring. This means you can only perform so much of it before it becomes too much.
Training in different heart rate zones improves slightly different physiological qualities, and so by spending time in each zone, you ensure a variety of benefits for performance and health.
So how much time should you spend in each zone?
Most elite endurance athletes, including runners, rowers, and even cross-country skiers, tend to spend most of their training (around 80%) in zone 1, with the rest split between zones 2 and 3.
Because elite endurance athletes train a lot, most of it needs to be in zone 1, otherwise they risk injury and burnout. For example, some runners accumulate more than 250 kilometres per week, which would be impossible to recover from if it was all performed in zone 2 or 3.
Of course, most people are not professional athletes. The World Health Organization recommends adults aim for 150–300 minutes of moderate intensity exercise per week, or 75–150 minutes of vigorous exercise per week.
If you look at this in the context of heart rate zones, you could consider zone 1 training as moderate intensity, and zones 2 and 3 as vigorous. Then, you can use heart rate zones to make sure you’re exercising to meet these guidelines.
What if I don’t have a heart rate monitor?
If you don’t have access to a heart rate tracker, that doesn’t mean you can’t use heart rate zones to guide your training.
The three heart rate zones discussed in this article can also be prescribed based on feel using a simple 10-point scale, where 0 indicates no effort, and 10 indicates the maximum amount of effort you can produce.
With this system, zone 1 aligns with a 4 or less out of 10, zone 2 with 4.5 to 6.5 out of 10, and zone 3 as a 7 or higher out of 10.
Heart rate zones are not a perfect measure of exercise intensity, but can be a useful tool. And if you don’t want to worry about heart rate zones at all, that’s also fine. The most important thing is to simply get moving.
Hunter Bennett, Lecturer in Exercise Science, University of South Australia
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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