De-Blackboxing the Health Features of Apple Watch

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Tianyi Zhao


Apple Watch, firstly launched in 2015 and having evolved to the fourth generation in 2018, is the smartwatch designed and marketed by Apple Inc. As a young and featuring product of Apple’s ecosystem with well-designed physical appearance and practical functions, Apple Watch has already highly praised and favored by customers. The success of Apple Watch depends on its unique design principles and theories. The thesis examines Apple Watch Series 4 from the overall system view, modularity, affordances and constraints. Then the paper will focus on the health function by analyzing its interface and internet within other Apple devices.

I. System View and Modularity

“Good design is a renaissance attitude that combines technology, cognitive science, human need, and beauty to produce something that the world didn’t know it was missing.” – Paola Antonelli, 2001

And here comes Apple Watch.

Smartwatch, removing the sparkling diamonds, precious metals and intricate features of the mechanical watch, shows as an integral whole so that it seems undetachable as a black-boxed device. However, when we look inside Apple Watch, it is a complex system with a relational structure of “interconnected, interdependent or mutually constitutive elements,” which is decomposable into many subsystems, and each can be managed semi-autonomously from the whole system. (Irvine, 2018)

By leveraging with the modular design principle, it is simple to unveil the complexity hidden by the various designs. Inside Apple Watch with the elaborate design and the tiny body, the system can be surprisingly broken down into eight main modules, including the components like case, display screen, S4 chip, the Digital Crown, three heart sensors, speaker, microphone, battery, removable bands and etc. which are “orchestrating” the combined modules into a system. The main modules and features show as below:

Case – Made of aluminum with three choices of colors: space grey, silver and gold.

Display Screen – There are two screen sizes 44mm and 40 mm. LTPO OLED Retina display with a resolution of 368 by 448 (44mm) and 324 by 394 (40mm). Support Force Touch with 1000 nits brightness.

S4 Chip – The processor with 64-bit dual-core processor. It is the complete System in Package (SiP) with the entire system fabricated onto a single component, empowering Apple to pack multi-functions and capabilities into a tiny body.

The Digital Crown – Made of aluminum with a built-in titanium electrode to measure heart rate by touching with a finger. During navigation without obstructing the display, the haptic feedback delivers a precise, click-like feel as user scrolls.

Heart Sensors – There are two kinds of sensors—electrical and optical sensors. The two electrical heart sensors include Digital Crown Electrode on the side and Back Crystal Electrode to generate an electrocardiogram and send to user’s doctor in real time. The optical heart sensor, equipped from the first generation, is for user’s quick check.

Figure 1. Heart Sensors on Apple Watch Series 4


Speaker & Microphone – The speaker is on the left side with a large area. The microphone is relocated to the right side for reducing echo.

Battery – built-in rechargeable lithium-ion battery, guaranteeing up to 18 hours.

Removable Bands – There are abundant colors and materials of watch bands that can be changed and slide into the band slots to satisfy the need of personalization.


II. Affordances and Constraints

Donald A. Norman defines affordances as the “perceived and actual properties of the thing, primarily those fundamental properties that determine just how the thing could possibly be used.” (Norman, 9) Apple Watch, designed as a wearable technology, is convenient for users to carry everyday with tiny size and light weight. As for the detailed components, to ensure the effectiveness, their affordances have been designed more perceivable and discoverable. The display screen affords to be touched, meanwhile where to touch depends on context specifically determined by the user interface. With a textured grip and as an extrusion on the exterior side, it is clear for users that the Digital Crown can be both rotated and pressed; also, the red circle on the top of crown, which indicates the electrocardiogram, guides users to touch with finger. Likewise, the flat button, located under the Digital Crown, is easily to be recognized by being slightly curved. It is obvious that the affordances of Apple Watch also reveal the indispensability of visibility, which emphasizes that systems are more usable when they clearly indicate their status so that the possible actions can be performed. (Lidwell, 202)

Oppositely, constraints “limit the possible actions that can be performed on a system.” (Lidwell, 50) Besides the convenience, the absolutely minuscule screen of Apple Watch, to a great extent, restricts user interaction. Firstly, information presentation and data input are highly limited. To guarantee the information delivery accurately and in time as well as to maximize reader’s understanding, there are only keywords showing on each alert or notification. The lack of keyboards forces users to fully depend on voice dictation. Secondly, the tiny size causes the emergence of the “fat finger problem.” When users put their finger over the watch screen, for the most time it covers almost 30 percent of the interaction space. Then, Apple Watch performs as an accessory or companion of iPhone instead of a standalone product. The heavy dependence is embodied in the mandatory pair with an iPhone if the user would like to explore more functions besides clock. At last, the limited battery life is also a significant issue. The maximum of 18 hours can hardly satisfy the daily need, especially for the people who usually stay outdoors for a long time. Apple Watch is marketing itself as a good companion to “help you stay even more active, healthy, and connected.”1 But the restricted battery life cannot help abide by its value.


III. Health Function

Apple Watch becomes more than a time-telling wearable, but rather a message notifier and consumer medical device. Health and fitness have been the new selling highlights to attract customers. In this part, the author will study how user interact with Apple Watch during workouts and the graphic design principles for application icons.

A. User Interaction

Due to the limited space and tiny body, there are many interactions of health function being blackboxed in Apple Watch, simplifying the user’s daily life. “Now, with the potential of Health Records information paired with HealthKit data, patients are on the path to receiving a holistic view of their health. With the Health Records API open to our incredible community of developers and researchers, consumers can personalize their health needs with the apps they use every day,” said Jeff Williams, Apple’s Chief Operating Officer. The analysis of how Apple Watch achieves it includes gesture interaction and semiotic icons.

1.Gesture Interaction

Since Alan Kay proposed the concept of “metamedia” interfaces, the awareness – that displays are not simply passive representational substrates of results or states but can be designed to take input as instructions or choices back into a computing process – has prevailed. Apple Inc. goes further than the creation of iPad in 2010. It has reinvented watch with interactive display and built-in modules and functions to maximize human-computer interaction, which optimizes user experience effectively. It not only contains the gestures “swipe,” “tap,” and “press” like smartphone does, but also recognizes physical gestures including wake-up and sleep, fall detection, heart rate monitoring and automatic workout detection. The technology hidden behind is the utilization of accelerometer – which measures changes in motion – and gyroscope – which detects the rate of rotation along three different axes.

Quick Wake-Up and Sleep – Apple Watch can be simply activated by raising user’s wrist or press the Digital Crown; likewise, it goes to the sleep mode when user lowers wrist. The design that accurately detects the rotation simplifies the process when users are doing sports or in any other motion.

Fall Detection and Emergency – The accelerometer and gyroscope, collaborating with a long-time research and its own algorithms of Apple Inc., work together to achieve fall detection. The accelerometer can measure 32 Gs of forces, which empowers Apple Watch to assume a big impact spike that a hard fall can create. Simultaneously, gyroscope is in charge of measuring the rotation rate and visualizing the different ways it does this rate by leveraging three-dimension analysis. It pictures “an axis going horizontally across the screen (the X axis); another one going vertically up the display (the Y); and finally a third sticking straight out through, and perpendicular to, the screen (the Z).” (Rob Verger) If there is a hard fall detected, the system immediately sends out a severe fall alert so that user can call for emergency help or ignore the warning. If the user is moving, Apple Watch waits for user’s response. However, if the watch detects that user has been immobile for about a minute, it will call emergency services and send a message to the emergency contacts with current location automatically.

Figure 2. The Alert Interface after Apple Watch’s Fall Detection


Heart Rate Monitoring – As each beat of the heart transmits an electrical impulse, Apple Watch can accurately read and record these impulses by combining the circuit between the user’s heart and both arms with three sensors. Apple Watch starts and continues to capture and record heart rate whenever user wears it. When Apple Watch detects unusually high or low heart rates or irregular heart rhythms like atrial fibrillation, it alerts the user to the irregularities, so that in-time action will be taken.

Figure 3. Reading Heart Rate with Digital Crown Electrode


Figure 4. Real-time Heart Rate Result


Figure 5. The Alert Interface When Irregular Heart Rate Detected


Automatic Workout Detection – Apple Watch is capable of detecting user’s activities, including walking, running, swimming, elliptical and rowing. The user gets reminders to start a workout and end one with an assumption of the specific workout type when the watch senses the user’ current activity status, during which it gives credit for the exercise the user has already started. Based on personal experience, the operation procedure is so easy and comfortable for the user that he/she would not be distracted when warming up or cooling down.

Figure 6. Reminders of Start and End Work Out



2. The Graphic Design of Icons

On the Home Screen of Apple Watch displays all applications downloaded on the watch, which show in circular shape and are the adapted version of applications on the smartphone. Because of the limited screen size, there are quantities of restrictions of Home Screen icons design. Generally, there are three main rules for Home Screen icons design – simplicity, focus point and similarity.

Figure 7. Home Screen Icons Collection


Simplicity – The icon includes a single element that concentrates the essence of the application in a simple and unique shape. For example, the icon of Phone app is designed with the element of phone; Workout app is obviously displayed with a person in motion; and an envelope signifies the email app effectively.

Figure 8. Icons of Phone, Workout and Email


Focus Point – The icon succeeds capture user’s attention and clearly identifies the application with a focused point. Among the examples discussed above, the phone, a person in motion and the white envelope perform as the focus points to guide user to understand accurately.

Similarity – Application icons on watch OS should maintain similarity to the iOS version. This principle requires designers to make an association between them by using a similar appearance and color palette, which helps user recognize fast and correctly. For instance, the iOS icon and watchOS icon share the same blue background. However, the brand name has been shortened from “Booking” on iOS to “B.” on watchOS to reduce user’s visual pressure on such small screen.

Figure 9. iOS icon vs watchOS icon



B. Apple Ecosystem with Internet

Having been struggling to invent and upgrade for year, Apple Inc. has already established an ecosystem with featuring products. Apple Watch, focusing on health functions, has not only practically expand market in sports and fitness lovers but also optimize common users’ healthy life. In both hardware and software levels, Apple Watch realizes real-time detection and record user’s exercise status and health conditions by building an internet with other Apple devices, like iPhone and MacBook.

Hardware Internet – The first thing when the user gets a new Apple Watch is to pair with an iPhone by scanning the animation on the watch. After setting up the watch via iPhone, the user can start use it with the Bluetooth connection with iPhone. Likewise, Apple Watch can also pair with MacBook to simplify the usage, for example, MacBook can automatically wake up when the user is wearing the paired Apple Watch.

Figure 10. The Pairing Process of Apple Watch and iPhone


Software Internet – Connection via Bluetooth enables Apple Watch to record and update the fitness and health conditions. The HealthKit – an Apple designed bundle that takes a collaborative approach to building a personalized health and fitness experience, including activity, mindfulness, nutrition and sleep – provides a central repository for health and fitness data on iPhone and Apple Watch. In other words, Apple Watch is an activity detector and data recorder, while iPhone serves as a data manager. The internet distributes different works to Apple Watch and iPhone. Conversely, the complementary relationship deepens the significance and indispensability of Internet.

Figure 11. Monthly Data Collection of Heart Rate

Many people believe Apple Watch help them cure iPhone addiction and cultivate a better behavior to improve self-management. However, inside the over-tight Internet with iPhone, Apple Watch becomes an accessory instead of a standalone product. For a better performance, Apple Watch should be within the Bluetooth range, and the Bluetooth and Wi-Fi need to be enabled permanently on the phone.  Personally, I deem that there are two ways to make Apple Watch to be an independent product. Firstly, Apple can take full advantage of iCloud in the process of setting up and syncing. There is no need to pair with an iPhone, but with the user’s iCloud ID; similarly, the data update can also be achieved via iCloud instead of Bluetooth. Secondly, Apple Watch should be differentiated from iPhone, because it is tedious to receive the same notifications twice, both on the watch and on the phone. Rather, the third-party applications can be eliminated from the watchOS, and adding the missing apps – such as Notes, Podcasts, Voice Memos and etc. – is necessary. Apple Watch can never be separated from the over-dependence with iPhone with the lack of essential apps and the redundancy of repeating functions.



Apple Watch has been one of the most featuring Apple products since its debut in 2015. The design principles hidden inside the tiny body are various and complex, empowering the wearable more multi-functional and practical. De-blackboxing Apple Watch in a system view, it is surprising to explore the complexity with many subsystems or modules. Modularity allows users to manage the complex whole structure of the watch by breaking its functions into separate and interconnected components. It is quite clear to understand how display screen, chip, battery, heart rate sensors, the Digital Crown and etc. work together as various sub-components. Affordances and constraints generated by elaborate designs diversify and help Apple optimize the watch to satisfy the users’ demands by annual evolvement. Health function, as the most attractive selling point, transforms Apple Watch from time-reader to the “ultimate workout partner.” The user interaction is based on multiple gesture detection, collaborating with the built-in algorithms. The graphic design on the home screen icons also simplifies the daily use and process, associating with the health and fitness highlights. At last, as a key product in the Apple ecosystem, users enjoy the convenience brought by its dependence with iPhone. However, the over-tight Internet predicts that the future market share Apple Watch will be totally tied to the prevalence of iPhone. Thus, here I propose two solutions that upgrading with the utilization of iCloud and focusing on differentiation from iPhone in some functions, which will help Apple Watch to change the embarrassing positioning as an individual product and embrace further breakthroughs.


Works Cited

Allison, Conor. “And finally: Apple Watch Series 4 detects AFib with 98% accuracy, says Heart Study.” Wearable, Sep. 16, 2018.

Bower, Graham. “iPhone dependence is killing Apple Watch. Here’s how Cupertino could fix it.” Cultofmac, Apr. 19, 2018.

Hale, James Loke. “How Does Apple Watch Health Work? Here’s Everything The Device Can Do For Your Well-Being.” Bustle, Apr. 19, 2018.

Irvine, Martin. “Introduction to Affordances, Constraints and Interfaces.” 2018.

Kaufman, Lori. “How to Rearrange the App Icons on Apple Watch.” How-to Geek, Dec. 17, 2015.

Lidwell, William., et al. Universal Principles of Design. Rev. and updated ed., Rockport Publishers, 2010.

Michaels, Mary M. “The Apple Watch Case Study: What we can learn and apply from an affordance analysis.” Human Factors International, 2015.

Norman, Donald A. The Design of Everyday Things. Basic Books, 2003.

Jeffries, Adrianne. “Why There Aren’t More Apple Watch Apps, According to Apple Watch Developers.” Motherboard, July 21, 2015.

Verger, Rob. “The Apple Watch learned to detect falls using data from real human mishaps.” Popular Science, Oct. 2, 2018.

Wallas, Paul. “Apple Watch; UI and UX Review.” Medium, May 28, 2017. Accessed on Dec. 12, 2018.

Apple Developer. Accessed on Dec. 12, 2018.