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Are Smartwatches and Fitness Trackers Worth the Hype?

Smartwatches and fitness trackers have gained popularity in recent years, for gym-rats and health-conscious people. But what's behind the hype about Apple Watches, Whoop bands, and Oura rings?

From their inception, these wearable devices have promised to revolutionize how we monitor and manage our health, sleep, readiness, recovery, and fitness.

In this article, we delve into the reasons behind their widespread adoption, exploring why people turn to these gadgets for everything from tracking workouts to monitoring sleep patterns.

I want to make clear and uncover whether smartwatches and fitness trackers truly live up to their promise as essential tools for optimizing health and fitness or if they're just a waste of money.

fitness tracker

Are Smartwatches and Fitness Trackers Really Make a Difference for Improving Health and Fitness?

Almost everyone wears smartwatches and fitness trackers on their wrist these days. But how valid and reliable are the measurements for estimating steps, distance, activity, energy consumption and sleep and what potential can wearables still develop?

In-depth knowledge for your new & fit self.

Digital wearables have become an integral part of today's fitness world. 

  • People who simply want to live an active lifestyle

  • professional bodybuilders and top athletes

  • as well as people who are ill and want to actively do something about their illness

are all using wearables these days. 

The incredibly rapid advances in wearable technology offer a growing variety of possible functions: from thermometers, barometers, magnetometers, accelerometers to oximeters and calorimeters.

Wearables can now be used to track not only steps, but also running distance, heart rate, body temperature, training load, sleep quality and, with some, even fertility and oxygen saturation.

As the popularity and use of wearables increases for both recreational and professional athletes, as well as the health sector, it is becoming increasingly important to understand the strengths, weaknesses and limitations of the technologies. 


While the quality of measurement accuracy varies enormously between different wearables providers, there are some measurement parameters that are still far from reality in terms of accuracy for almost all wearables.

Other measurement parameters, on the other hand, appear to be becoming increasingly accurate and reliable. Especially for the healthcare sector, it is important to continue to analyze the accuracy and effectiveness of wearables to determine whether the measurement results of wearables are reliable.

For anyone who owns a wearable and wants to improve their health or fitness, it makes sense to know which parameters can be relied on to make smart adjustments in everyday life. A better understanding can help to make better everyday decisions, for example to improve performance, regeneration or health.

fitness tracker

The Truth Behind the Numbers: The Reliability of Smartwatch Measurements

Reliable Measurement Parameters

Activity in everyday life

The step count has achieved the greatest accuracy in most studies and meta-analyses. So if we want to wear a fitness watch just to know how many steps we take a day and what our daily activity level is, then classic fitness watches are relatively reliable nowadays and a good tool for finding out more about our own activity.

So we know with a relatively high degree of certainty that everyday activity in the form of the number of steps and non-sporting movements such as household chores, walking stairs or physical work can be measured relatively accurately with most wearables. It is very interesting that many studies show that simply wearing a fitness watch helps and motivates people to move more in everyday life. 

According to studies in which the effect of fitness trackers was specifically investigated, this effect has a positive influence on:

  • blood pressure

  • body composition (proportion of fat and muscle)

  • general fitness

  • cholesterol levels

The reason for the positive changes is usually increased physical activity and an increased number of steps.

But why does wearing a fitness tracker automatically increase activity?

There is no clear answer to this question, but it is probably a combination of monitoring (seeing how much you move or how little you move), setting goals (for example, to reach 10,000 steps a day) and the regular reminders to move that are shown on the displays of the wearables. A wearable can therefore be a great motivator if you want to live a more active and healthier life.

Heart rate & HRV

While medical wearables that are specifically designed to detect cardiovascular diseases have a relatively high accuracy and can sometimes detect diseases early enough (such as cardiac arrhythmias or atrial fibrillation), the vast majority of wearables on the public market do not have this capability.

So if you want precise information about your heart health, or if you suspect that you are suffering from a cardiovascular disease, you should use an EEG method or similar in consultation with a doctor.

However, non-commercial wearables and fitness trackers are relatively reliable when it comes to measuring heart rate or heart rate variability.

Heart rate variability (HRV) is one of the most useful physiological measures for detecting stress or recovery.

With good measurement and evaluation, HRV can even provide information about anxiety or depressive moods, as these are strongly influenced by HRV. 

However, the few wearables that measure HRV in addition to heart rate do not provide any information about mental well-being, but only about regeneration. On this basis, most wearables give recommendations on what should be done from a fitness point of view, for example whether a light workout should be carried out, a break should be taken or full throttle can be given during training.

Wearables that measure HRV are currently not yet good enough to provide a clear analysis of a person's mental state, only stress levels can be measured reasonably well. 

However, the wearables currently available on the market usually only measure the average heart rate. With heart rate alone, stress and regeneration cannot be assessed as accurately as is possible with HRV measurements. However, the heart rate can be used to determine how intense a workout was, for example.

Limits of Smartwatch Measurements

Energy Expenditure

Determining a person's exact and real energy expenditure is not as easy as it sounds, as the only truly reliable method for this is indirect calorimetry. In indirect calorimetry, the amount of heat is calculated using the measured oxygen expenditure, usually through a breathing mask. 

Most wearables therefore fail to accurately determine calorie expenditure. Most studies show that, depending on the model of the tracker, calorie expenditure is very often over- or underestimated. 

Some wearables are slightly more accurate than others. The reason for the general inaccuracy is that the measurements used to calculate the energy expenditure of most wearables are based solely on heart rate and movement throughout the day. 

Individual factors that influence calorie expenditure, such as 

  • body fat 

  • muscle percentage 

  • and individual metabolism

are not taken into account.

The more factors are taken into account (age, gender, height), the more accurate the statements on energy expenditure can be. 

Nevertheless, there are also some individual studies that show that the accuracy of some trackers is between 70-90%, but this accuracy does not apply to most common trackers.

Moreover, a person's calorie expenditure is not a fixed number, but a value that fluctuates from day to day, depending on how much you move. However, wearables can be reliable if you want to identify trends in daily expenditure . 

For example, if calorie expenditure has been around ~2500 calories a day for a long period of time and you suddenly integrate more exercise into your daily routine (e.g., more training or more walks), and this increases your expenditure to around ~3000 calories a day (according to the wearable) over a longer period of time, then we shouldn't take the exact numbers too serious, but at least we know with a relatively high degree of certainty that the expenditure trend is moving in one direction.

If you want to lose or gain weight, you shouldn't rely entirely on the calorie expenditure data from a tracker. However, the numbers can be used as a reference point from which to start and make adjustments over time

sleep tracker


When it comes to sleep tracking accuracy, you should not rely 100% on what a tracker says, although the measurements do seem to be slightly more accurate than those for energy expenditure.

Many wearables overestimate sleep time and interpret that you are sleeping even though you are just lying still in bed without moving. Even lying down to meditate while awake can easily be interpreted as sleeping. For this reason, most wearables overestimate sleep quality or efficiency, often referred to as "sleep score".

On the other hand, waking up during the night is either overestimated or underestimated by many trackers. Some wearables interpret movement during sleep as being awake, others as being asleep, or as REM sleep.

Some people feel stressed by wearing a sleep tracker, which can eventually lead to a worsening of sleep. At this point, everyone should decide for themselves whether sleep tracking is beneficial or detrimental to their own sleep quality.

"If you're someone who easily becomes fixated and stressed by numbers, a sleep and activity tracker might not be the best choice for you."

Fertility and the Female Cycle

During the female cycle, a woman's temperature fluctuates depending on the phase of the cycle. Many women nowadays use the basal body temperature method for contraception, where body temperature is measured daily in the morning either vaginally or rectally. 

Some fitness trackers can measure temperature on the skin surface. However, most common wearables do not possess the function and algorithm to predict the cycle or fertility. 

Nevertheless, an interesting study was conducted where wearables measured women's temperature on the wrist while simultaneous ovulation tests were conducted. Surprisingly, the wearables were correct in measuring fertility about 82% of the time.

According to the researchers, well-developed wearables could potentially be used in the future as a relatively reliable method for contraception or family planning. However, there is still a definite need for further research and adjustments to most wearables for this specific function. 

The so-called Oura Ring, worn on the finger, and the accompanying app "Natural Cycles," is the first wearable approved by the FDA as a birth control app. This indicates a great interest, as more and more women want to use hormone-free contraception methods.

Conclusion About The Accuracy of Smartwatches and Fitness Trackers

We can hope that in the future, more investment will be made in the research and improvement of wearables. Wearables have great potential to be increasingly used in the medical field, to detect diseases early, support family planning, or even better measure individuals' mental states.

Current studies show that the accuracy of trackers varies greatly from model to model, and each model has its strengths and weaknesses in some area. Compared to the first trackers on the market, the accuracy and measurement quality have already improved enormously, and we can increasingly trust these devices.

Some functions, such as the early detection of heart diseases or mental illnesses due to stress, can primarily be detected by medical devices rather than commercial fitness trackers. It remains exciting to see where the future of wearables will lead.

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Sources Of Information:

  • Ferguson, T., Olds, T., Curtis, R., Blake, H., Crozier, A. J., Dankiw, K., Dumuid, D., Kasai, D., O'Connor, E., Virgara, R., & Maher, C. (2022). Effectiveness of wearable activity trackers to increase physical activity and improve health: a systematic review of systematic reviews and meta-analyses. The Lancet. Digital health, 4(8), e615–e626.

  • Germini, F., Noronha, N., Borg Debono, V., Abraham Philip, B., Pete, D., Navarro, T., Keepanasseril, A., Parpia, S., de Wit, K., & Iorio, A. (2022). Accuracy and Acceptability of Wrist-Wearable Activity-Tracking Devices: Systematic Review of the Literature. Journal of medical Internet research, 24(1), e30791. 

  • Prieto-Avalos, G., Cruz-Ramos, N. A., Alor-Hernández, G., Sánchez-Cervantes, J. L., Rodríguez-Mazahua, L., & Guarneros-Nolasco, L. R. (2022). Wearable Devices for Physical Monitoring of Heart: A Review. Biosensors, 12(5), 292.

  • Hickey, B. A., Chalmers, T., Newton, P., Lin, C. T., Sibbritt, D., McLachlan, C. S., Clifton-Bligh, R., Morley, J., & Lal, S. (2021). Smart Devices and Wearable Technologies to Detect and Monitor Mental Health Conditions and Stress: A Systematic Review. Sensors (Basel, Switzerland), 21(10), 3461.

  • Evenson, K. R., Goto, M. M., & Furberg, R. D. (2015). Systematic review of the validity and reliability of consumer-wearable activity trackers. The international journal of behavioral nutrition and physical activity, 12, 159.

  • Mohaned Shilaih, Brianna M. Goodale, Lisa Falco, Florian Kübler, Valerie De Clerck, Brigitte Leeners; Modern fertility awareness methods: wrist wearables capture the changes in temperature associated with the menstrual cycle. Biosci Rep 21 December 2018; 38 (6): BSR20171279. doi:


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