People have a pretty intuitive sense of what is healthy – standing is better than sitting, exercise is great for overall health and getting good sleep is imperative.

However, if exercise in the evening may disrupt our sleep, or make us feel the need to be more sedentary to recover, a key question emerges – what is the best way to balance our 24 hours to optimise our health?

Our research attempted to answer this for risk factors for heart disease, stroke and diabetes. We found the optimal amount of sleep was 8.3 hours, while for light activity and moderate to vigorous activity, it was best to get 2.2 hours each.

Finding the right balance

Current health guidelines recommend you stick to a sensible regime of moderate-to vigorous-intensity physical activity 2.5–5 hours per week.

However mounting evidence now suggests how you spend your day can have meaningful ramifications for your health. In addition to moderate-to vigorous-intensity physical activity, this means the time you spend sitting, standing, doing light physical activity (such as walking around your house or office) and sleeping.

Our research looked at more than 2,000 adults who wore body sensors that could interpret their physical behaviours, for seven days. This gave us a sense of how they spent their average 24 hours.

At the start of the study participants had their waist circumference, blood sugar and insulin sensitivity measured. The body sensor and assessment data was matched and analysed then tested against health risk markers — such as a heart disease and stroke risk score — to create a model.

Using this model, we fed through thousands of permutations of 24 hours and found the ones with the estimated lowest associations with heart disease risk and blood-glucose levels. This created many optimal mixes of sitting, standing, light and moderate intensity activity.

When we looked at waist circumference, blood sugar, insulin sensitivity and a heart disease and stroke risk score, we noted differing optimal time zones. Where those zones mutually overlapped was ascribed the optimal zone for heart disease and diabetes risk.

You’re doing more physical activity than you think

We found light-intensity physical activity (defined as walking less than 100 steps per minute) – such as walking to the water cooler, the bathroom, or strolling casually with friends – had strong associations with glucose control, and especially in people with type 2 diabetes. This light-intensity physical activity is likely accumulated intermittently throughout the day rather than being a purposeful bout of light exercise.

Our experimental evidence shows that interrupting our sitting regularly with light-physical activity (such as taking a 3–5 minute walk every hour) can improve our metabolism, especially so after lunch.

While the moderate-to-vigorous physical activity time might seem a quite high, at more than 2 hours a day, we defined it as more than 100 steps per minute. This equates to a brisk walk.

It should be noted that these findings are preliminary. This is the first study of heart disease and diabetes risk and the “optimal” 24 hours, and the results will need further confirmation with longer prospective studies.

The data is also cross-sectional. This means that the estimates of time use are correlated with the disease risk factors, meaning it’s unclear whether how participants spent their time influences their risk factors or whether those risk factors influence how someone spends their time.

Australia’s adult physical activity guidelines need updating

Australia’s physical activity guidelines currently only recommend exercise intensity and time. A new set of guidelines are being developed to incorporate 24-hour movement. Soon Australians will be able to use these guidelines to examine their 24 hours and understand where they can make improvements.

While our new research can inform the upcoming guidelines, we should keep in mind that the recommendations are like a north star: something to head towards to improve your health. In principle this means reducing sitting time where possible, increasing standing and light-intensity physical activity, increasing more vigorous intensity physical activity, and aiming for a healthy sleep of 7.5–9 hours per night.

Beneficial changes could come in the form of reducing screen time in the evening or opting for an active commute over driving commute, or prioritising an earlier bed time over watching television in the evening.

It’s also important to acknowledge these are recommendations for an able adult. We all have different considerations, and above all, movement should be fun.

Christian Brakenridge, Postdoctoral research fellow at Swinburne University Centre for Urban Transitions, Swinburne University of Technology

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

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.