# Fitness tracker

A fitness tracker or activity tracker is an electronic device or app that measures and collects data about an individual's movements and physical responses in order to monitor and improve their health, fitness, or psychological wellness over time.
Fitness trackers are a more sophisticated version of the pedometer; in addition to counting steps, they contain additional sensors such as accelerometers and altimeters to collect or estimate information, including the speed and distance travelled, heart rate, calorie expenditure, or the duration and quality of sleep.
Improvements in computing technology since the 1980s, recently driven by the rapid advancement of smartphones, paved the way for the spread of wearable tracker devices with integrated sensors. A large amount of sensitive sensor and user-input data is synced with mobile apps such as fitness, mood, sleep, water intake, medicine usage, sexual activity, menstruation, and potential illnesses. The large volume of data colected has led to privacy concerns around how consumer information is stored and analyzed by the companies involved.

## History

Wearable heart rate monitors for athletes were available in 1981. Improvements in technology in the late 20th and early 21st century made it possible to automate the recording of fitness activities, as well as to integrate monitors into more easily worn equipment. The RS-Computer shoe was released in 1986. Early examples include wristwatch-sized bicycle computers that monitored speed, duration, distance, etc., available at least by the early 1990s. By at least the early 2000s, wearable fitness tracking devices were available as consumer-grade electronics, including wireless heart rate monitors that could be connected to commercial-grade exercise machines in gyms. Athletes are usually tracked with the levels of internal and external loads, where external loads will consist of the performance outcomes usually witnessed by coaches, and internal loads consist of factors such as heart rate, blood pressure, and blood lactate levels. When taking into account the well-being of the subject, subjective scales are involved which measure fatigue, sleep quality, emotions, and soreness.
Fitness trackers later diversified to include wristbands and armbands (so-called smart bands) and smaller devices that could be clipped wherever preferred. In 2006 Apple and Nike released the Nike+iPod, a sensor-equipped shoe that worked with an iPod Nano.
By 2010, logging apps had been introduced, many of which enabled the direct sharing of data to Facebook ot Twitter. Fitness trackers became appealing to consumers because of the combination of gamification, the social dimension of sharing via social media, and increased motivation due to the resulting rivalry and competition between friends.
In 2016, there were several advances made regarding fitness tracking geared toward kids with a variety of options from organizations such as UNICEF and Garmin.

## Tracker formats

Most consumer fitness trackers are worn on a wristband similar to a wristwatch. This type of tracker usually includes a digital display for data. Wrist-based trackers may be prone to error during exercise involving rapid arm motion.
Some fitness trackers take the form of a ring. Ring-based trackers have no display of their own and rely on a connection with a smartphone to display tracked data.
Another low-profile format for fitness trackers places sensors inside of earphones. These trackers rely on a smartphone to display data, similar to ring-based trackers. Earphone-based fitness trackers use sensors to take readings directly from the capillaries located within the ear. Due to their placement, these trackers can give more accurate results for blood pressure, electrocardiogram, and body temperature. Fitness trackers placed in the ear are also well suited to the assessment of heart rate.

### Activity tracking on smartwatches

Many devices primarily intended as smartwatches also function as fitness trackers. An early example was the Apple Watch, which has offered fitness tracker functions since 2014.

## Tracker apps

The standard activity-tracking smartphone or web apps present data in statistical form meant to be viewed after the activity has ended. However, research suggests that if we want a richer understanding of the data, we need intelligent computing to be included in the systems that run the apps.

## Performance problems

Certain movements of the user can distort the results obtained from fitness trackers as seen in a test conducted by Stiftung Warentest where the products were unable to accurately track a bike ride. Furthermore, the determined values for the human energy transformation were erroneous. With the heart rate large deviations have been observed at wristlet trackers, and it is recommended for this purpose to use appropriate chest straps. Wristbands can be uncomfortable to wear and inadvertently be lost. For some products, genotoxic substances were detected.

## Privacy concerns

There have been some privacy issues regarding the data collection of activity-tracking apps, a user's health can be tracked into a "digital health footprint". There have been many concerns about privacy issues with menstruation and reproductive health-tracking apps. Many women who use these apps for menstrual and contraceptive tracking are under the impression that their data is private when there is no single body regulating the apps, making the availability and protection of the data unknown.
The apps of some fitness trackers not only transmit personal data but also private address lists to servers on the Internet without notifying or asking the user. Even when anonymized, the mere presence of geolocation data may be a national security risk. However, the results of a study among semi-professional (half-) marathon participants suggest that certain users are open to sharing tracked activity data voluntarily.
In the US in 2013, BodyMedia developed a disposable fitness tracker to be worn for a week, which is aimed at medical and insurance providers and employers seeking to measure employees' fitness. In 2014, Jawbone developed a system called UP for Groups which could provide employers with aggregated data from employees' wearable fitness trackers and apps.

## Psychological impacts

Research has been carried out on the gamification of health apps, where users earn incentives and rewards based on their health goals. Though this can make the app engaging, there was concern it could trivialize health apps and deter the users from their genuine health goals. There is also research problematizing tracking devices about how we inhabit, experience, and imagine our bodies and lives.

## Wearable sensors

Wearable sensors have been widely used in medical sciences, sports, and security. Wearable sensors can detect abnormal and unforeseen situations, and monitor physiological parameters and symptoms through these trackers. This technology has transformed healthcare by allowing continuous monitoring of patients without hospitalization. Medical monitoring of a patient's body temperature, heart rate, heart rate variability, brain activity, muscle motion, and other critical data can be delivered through these trackers.
Moreover, in sports training, there is an increasing demand for wearable sensors. For example, measurement of sweat rate was possible only in laboratory-based systems a few years ago but is now possible using wearable sensors. Heart rate variability (HRV) has the potential to determine the quality of an exercise regimen. Additionally, HRV is recommended among the athletic community as a warning sign for over-training. In these ways, HRV can be used to optimize performance.

## Medical uses

Fitness trackers are not medical devices. However, newer models approach the US definition of a Class II medical monitor, and some manufacturers hope to eventually make them capable of alerting to a medical problem, although FDA approval would be required.

### Detection of atrial fibrillation

Activity tracking has been utilized to keep track of atrial fibrillation (AF), an irregular and chaotic heartbeat, which is accountable for a majority of strokes in the United States. Professionals rely on the ambulatory electrocardiogram (EKG) to record AF but soon found wearable wristbands to be useful for regular usage. These wearables must be accurate to prevent misdiagnosis, morbidity, and mortality. The Apple Watch was found in a study to be able to detect and notify the wearer of an irregular pulse. Though there is a risk of false positives, the study found that it may be a useful tool in the initial diagnosis process as a gateway to additional procedures rather than being the only tool used.

### Weight loss and obesity

Fitness trackers have also been used for tracking and finding solutions to combat obesity by promoting physical activity. A device called the Fitbit Alta was used as the wristband for adolescents who are considered obese where their steps, distance, calories burned, activity time, and sleep rates were kept track of and downloaded by the researchers to analyze. The overall study found that societal and cultural factors were what affected adolescent obesity given that low-income minorities were at a higher risk given that they had limited access to weight management programs and resources. The tracking of steps and amount of physical activity allowed for one to be aware of their habits and lifestyle, but the access to weight loss programs varied for many, which is why the researchers utilized this information and used the technology to correlate behavioral aspects with the data to search for more solutions.
One review of six studies found that there was little evidence that fitness trackers improve health outcomes. Of five studies that looked at weight loss, one found benefit, one found harm, and three found no effect. Another systematic review covering 35 studies and 7454 participants, published in the British Journal of Sports Medicine, found that fitness trackers increased people's physical activity by an average of 1850 steps/day.
According to another study comparing 8-week interventions and four-month follow-ups of physical activity monitors, a guided weight loss program, and together, activity monitoring and the weight loss program are associated with similar improvements and both combined are associated with more improvements than either alone. It is unclear whether activity changes occur in children and adolescents.

### Monitoring stress and mental illness

There are many apps available in the Apple AppStore and the Samsung Google Play Store that deal with mental health management and self-help. Smartwatches have also been involved in monitoring stress and other mental health issues. A study was done analyzing the different types of devices, ranging from bulky wearables to smaller, portable devices with sensors that can detect depression, anxiety, and any form of stress. Monitoring these main three factors is essential to understanding any risk and likelihood of additional health complications and the correlation to specific conditions. Chest patches are used for measuring heart rate while the wristbands ("Chillbands") were used to track activity, where a correlation was seen in the HR levels and the involvement of circadian rhythm, stress, gender, and age. It was seen that detecting depression alone was challenging, causing a risk of misdiagnosis, but further research along with tracking of sleep, physical activity, mood changes, cognitive function, and social habits will help towards accurate measurements.

### Monitoring infant growth development

Wearable sensors have also been in use when keeping track of infant development, motor skills, and physical growth are the main aspects that were focused on.

### Parkinson's disease prediction

Physical movement tracking can be used as a predictive analysis tool to determine the risk of Parkinson's Disease in individuals.

### Alerting for caregivers

Other fitness trackers are intended to monitor vital signs in the elderly, epileptics, and people with sleep disorders and alert a caregiver to a problem.

### Menstrual tracking and reproductive health

Individuals with a uterus can use menstrual tracking apps to keep track of their cycles and refer back to the timeline to spot any changes that they would like to bring up to their doctors or specialists. There are several apps for this purpose but the privacy and security of the data are unknown given that there is no one "head" that oversees the system, leaving a lot of the data open to the market, leaving many questions as to how secure the data is when entered. When users sign up for these apps, they are usually led with an "at your own risk" warning in case any data gets leaked, which can contribute to more targeted ads and inaccurate predictions in their cycles.

### Animal health

Fitness trackers have been designed for animals, for example collar-mounted fitness trackers for dogs.