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.

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.

When Kim Kardashian posted on Instagram about having had a full-body MRI, she enthused that the test can be “life saving”, detecting diseases in the earliest stages before symptoms arise.

What Kardashian neglected to say was there’s no evidence this expensive scan can bring benefits for healthy people. She also didn’t mention it can carry harms including unnecessary diagnoses and inappropriate treatments.

With this post in mind, we wanted to explore what influencers are telling us about medical tests.

In a new study published today in JAMA Network Open, we analysed nearly 1,000 Instagram and TikTok posts about five popular medical tests which can all do more harm than good to healthy people, including the full-body MRI scan.

We found the overwhelming majority of these posts were utterly misleading.

5 controversial tests

Before we get into the details of what we found, a bit about the five tests included in our study.

While these tests can be valuable to some, all five carry the risk of overdiagnosis for generally healthy people. Overdiagnosis is the diagnosis of a condition which would have never caused symptoms or problems. Overdiagnosis leads to overtreatment, which can cause unnecessary side effects and stress for the person, and wasted resources for the health system.

As an example, estimates suggest 29,000 cancers a year are overdiagnosed in Australia alone.

Overdiagnosis is a global problem, and it’s driven in part by healthy people having tests like these. Often, they’re promoted under the guise of early screening, as a way to “take control” of your health. But most healthy people simply don’t need them.

These are the five tests we looked at:

The full-body MRI scan claims to test for up to 500 conditions, including cancer. Yet there is no proven benefit of the scan for healthy people, and a real risk of unnecessary treatment from “false alarm” diagnoses.

The “egg timer” test (technically known as the AMH, or anti-mullarian hormone test) is often falsely promoted as a fertility test for healthy women. While it may be beneficial for women within a fertility clinic setting, it cannot reliably predict the chance of a woman conceiving, or menopause starting. However, low results can increase fear and anxiety, and lead to unnecessary and expensive fertility treatments.

Multi-cancer early detection blood tests are being heavily marketed as the “holy grail of cancer detection”, with claims they can screen for more than 50 cancers. In reality, clinical trials are still a long way from finished. There’s no good evidence yet that the benefits will outweigh the harms of unnecessary cancer diagnoses.

The gut microbiome test of your stool promises “wellness” via early detection of many conditions, from flatulence to depression, again without good evidence of benefit. There’s also concern that test results can lead to wasted resources.

Testosterone testing in healthy men is not supported by any high-quality evidence, with concerns direct-to-consumer advertising leads men to get tested and take testosterone replacement therapy unnecessarily. Use of testosterone replacement therapy carries its own risk of potential harms with the long-term safety in relation to heart disease and mortality still largely unknown.

What we found

Together with an international group of health researchers, we analysed 982 posts pertaining to the above tests from across Instagram and TikTok. The posts we looked at came from influencers and account holders with at least 1,000 followers, some with a few million followers. In total, the creators of the posts we included had close to 200 million followers.

Even discounting the bots, that’s a massive amount of influence (and likely doesn’t reflect their actual reach to non-followers too).

The vast majority of posts were misleading, failing to even mention the possibility of harm arising from taking one of these tests. We found:

• 87% of posts mentioned test benefits, while only 15% mentioned potential harms
• only 6% of posts mentioned the risk of overdiagnosis
• only 6% of posts discussed any scientific evidence, while 34% of posts used personal stories to promote the test
• 68% of influencers and account holders had financial interests in promoting the test (for example, a partnership, collaboration, sponsorship or selling for their own profit in some way).

Further analysis revealed medical doctors were slightly more balanced in their posts. They were more likely to mention the harms of the test, and less likely to have a strongly promotional tone.

As all studies do, ours had some limitations. For example, we didn’t analyse comments connected to posts. These may give further insights into the information being provided about these tests, and how social media users perceive them.

Nonetheless, our findings add to the growing body of evidence showing misleading medical information is widespread on social media.

What can we do about it?

Experts have proposed a range of solutions including pre-bunking strategies, which means proactively educating the public about common misinformation techniques.

However, solutions like these often place responsibility on the individual. And with all the information on social media to navigate, that’s a big ask, even for people with adequate health literacy.

What’s urgently needed is stronger regulation to prevent misleading information being created and shared in the first place. This is especially important given social media platforms including Instagram are moving away from fact-checking.

In the meantime, remember that if information about medical tests promoted by influencers sounds too good to be true, it probably is.

Brooke Nickel, NHMRC Emerging Leader Research Fellow, University of Sydney; Joshua Zadro, NHMRC Emerging Leader Research Fellow, Sydney Musculoskeletal Health, University of Sydney, and Ray Moynihan, Assistant Professor, Faculty of Health Sciences & Medicine, Bond University

This article is republished from The Conversation under a Creative Commons license. Read the original article.