# Why Zone Training According to Your Watch Actually Works
Everyone who has ever started taking running or cycling more seriously has sooner or later encountered the concept of training zones. Sports watches today can measure almost anything – heart rate, power, oxygen saturation and sleep quality – but all that data is worthless if you don't know what to do with it. Zone training is one of the most effective ways to stop training blindly and start truly managing your progress.
Take Martin, for example, a recreational runner who heads out every day on the same five-kilometre route at the same pace. After six months, he wonders why he isn't improving, why he's constantly tired, and why competitive runners easily overtake him in races. The answer is simple: Martin has been training the entire time at the same intensity, which is neither low enough for recovery nor high enough for development. Training zones are precisely the tool that helps avoid such traps.
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What training zones are and why they matter
Training zones are ranges of physical exertion intensity, most commonly expressed through heart rate or power, that correspond to different physiological processes in the body. At low intensity, the body burns predominantly fat and builds an aerobic base. At higher intensity, it switches to carbohydrates, lactate production increases, and the body learns to work under conditions of oxygen debt. Each zone therefore stimulates different adaptations and has its place in a training plan.
The most widespread system works with five zones, although some coaches and watch manufacturers use a system of three or seven zones. The five-zone model is sufficiently detailed for most recreational and performance athletes while remaining clear and manageable. Zone one corresponds to very light activity, such as brisk walking or gentle stretching. Zone two is the aerobic base – a pace at which you can converse without difficulty. Zone three is often referred to as "tempo" or "moderate intensity". Zone four corresponds to the anaerobic threshold and zone five is maximum effort, which can only be sustained briefly.
The scientific basis for this approach is solid. Studies published in the academic journal International Journal of Sports Physiology and Performance repeatedly show that athletes who consciously divide their training between low and high intensity – the so-called polarised or pyramidal model – achieve better results than those who train predominantly at moderate intensity. Moderate intensity, into which most recreational athletes instinctively drift, is paradoxically the least productive zone for long-term development.
The renowned Norwegian sports physiologist Stephen Seiler, who has spent decades researching training intensity, put it succinctly: "Elite endurance athletes spend approximately 80% of their training at low intensities and only 20% at high ones. The middle zone is no man's land."
How to correctly set zones on your watch
This is where the biggest problem arises. Most sports watches have training zones pre-set by the manufacturer based on general formulas, most commonly using maximum heart rate estimated from age (the standard formula of 220 minus age). This approach is convenient, but completely inadequate for individual zone setting. Maximum heart rate can differ by tens of beats per minute between people of the same age, and the general formula does not account for this variability at all.
The first step towards meaningful zone setting is therefore to determine your actual maximum heart rate – or, even better, your anaerobic threshold. The anaerobic threshold is the intensity at which lactate concentration in the blood begins to rise significantly, and it is one of the most important parameters of endurance performance. The most accurate measurement takes place in a laboratory during a so-called graded exercise test, but there are also reliable field alternatives.
One of the most widely used methods is the so-called lactate threshold test based on heart rate. It involves the athlete completing a 30-minute maximum effort (for example, a run or a bike ride), and the average heart rate from the second half of this test – that is, the last 20 minutes – corresponds approximately to the anaerobic threshold. Garmin, Polar and Suunto offer automatic lactate threshold detection in some watch models based on training data, but a manual test is still more accurate and is also recommended by the American College of Sports Medicine (ACSM).
Once you know your threshold heart rate, you can set zones manually. Zone one typically falls below 68% of maximum heart rate, zone two between 68 and 83%, zone three between 83 and 88%, zone four between 88 and 95%, and zone five above 95%. Different manufacturers and coaches use slightly different percentages, but these figures are a good starting point. The key is that your zone two genuinely corresponds to the aerobic base – that is, an intensity at which the body works efficiently without incurring an oxygen debt.
Zone settings vary by manufacturer. On Garmin, you'll find the options under User Profile → Heart Rate and Performance Zones. Polar allows settings directly in the Polar Flow app, where zones can be adjusted based on heart rate, power or pace. Suunto manages zones in the Suunto App and also offers the option of linking with test results. It's important to check whether the watch operates with zones based on maximum heart rate, or based on heart rate reserve (the so-called Karvonen method), because both methods produce different values – the Karvonen method is more accurate as it also takes resting heart rate into account.
How to use zone training in practice
Setting up zones is just the beginning. The real value comes only when you start consciously using training zones in both planning and executing your workouts. And this is where the biggest surprise awaits many athletes: training in zone two is much slower than most people expect.
On their first attempt at "slow aerobic training" in zone two, many are surprised at how significantly they need to slow down to keep their heart rate below the set threshold. For less trained individuals in particular, this may mean transitioning from running to walking. This is perfectly fine and is evidence that the aerobic base is weak and needs strengthening. Over weeks and months, aerobic capacity increases and a significantly higher pace can be maintained at the same heart rate – this is direct evidence of the body's adaptation.
A typical training week for an endurance athlete working with zones might look like this: three to four workouts in zones one and two, one workout in zone four (interval or threshold training), and possibly one short workout in zone five (sprints or maximum intervals). Zone three is deliberately omitted or minimised – it is an intensity that causes fatigue but brings no significant adaptive stimulus for either the aerobic base or anaerobic capacity.
Consistency in adhering to zones is more important than perfection. It is not necessary to complete every workout precisely according to the numbers – terrain, weather, fatigue or stress can all influence values. Sports watches are a great tool, but they are not an absolute authority. If you're going uphill and your heart rate crosses into zone three, it doesn't mean you've "ruined" the workout. What matters is the overall picture of training across weeks and months.
Wearables and sports watches have in recent years become part of a healthy lifestyle far beyond the boundaries of elite sport. Models such as the Garmin Forerunner, Polar Vantage or Apple Watch Ultra offer sophisticated tools for analysing training load, recovery and sleep. Their value, however, stands or falls on how well the user understands the data they provide. Zone training is in this sense a bridge between raw technology and genuine physiological understanding of one's own body.
It is also worth noting that training zones are not the exclusive domain of runners and cyclists. Swimmers, rowers, triathletes and people who regularly use an elliptical trainer or rowing ergometer can benefit from zone training equally. In strength training, the situation is more complex, as heart rate is not as reliable an indicator of intensity as in endurance sports, but there are ways to work with intensity in a structured manner here too – for example, through percentage of one-repetition maximum (1RM).
Zone training by watch is not a passing trend or the preserve of professional athletes. It is a way to stop training by feel and start training by data – with an understanding of what each workout brings to the body and why. For anyone who wants to get the most out of their physical activity while minimising the risk of overtraining and injury, it is one of the most valuable tools that modern sports technology has to offer. And the best part is that absolutely anyone can start – all you need is a watch, a little patience, and a willingness to go genuinely slowly from time to time.
