Plank Hero: Exercise the Right Way


This is a group project for Mobile & IoT Computing Services class. Working with two CS students and a MBA student, we designed and built an Android fitness app and won 2nd place out of 12 teams.


Yiding Ou (Developer)
Tian Liang (Developer)
Amber Xiao (Analyst)


User Research
UX/UI Design
User Testing


Google Forms

The home fitness market is on the rise since we are increasingly committed to a healthy lifestyle and yet have less time to hit the gym. Despite having various digital solutions, home fitness users are still facing challenges, especially around sustaining motivation and getting timely feedback.

How might we create a helpful and engaging home fitness experience that provides guidance, motivation, and feedback for casual workout users?
Plank Hero, a test case experimenting with new ways to provide motivation, guidance, and feedback for novice users through:
Video Feedback
Voice Command
Combat Game
Video Feedback
Voice Instruction
Gamified Experience


Guided Workout

The “Exercise Mode” allows users to learn, monitor, and receive feedback on their movements, in order to make up for the lack of guidance.

The user can select from multiple plank workouts, view the tips, and set a timer to start the workout.


Create Posture Reminder

After the work out, the user can review the workout recording and compare own posture to the tutorial. The user can set posture reminders like "Lower my hip" for next time and continue to improve.


Invite Friends to Battle

The “Battle Mode” creates a close-knit workout community in which users can challenge their friends for a workout battle and receive status, to keep the user engaged and motivated.


Generative Research

Exploratory Survey:
How are people currently working out at home?
Works Out At Home
Do Planks or Other Core

From a survey around current fitness habits and app usage behaviors, we learned that doing planks is very popular among home fitness users, which helped us narrow to a test module. In general, we found that although people enjoy the convenience of home workout, they often lack the motivation and guidance.

Major Findings:

01 Main motivation for home workout is to stay in shape.

Nearly half of the respondents cited "to be in better shape" as the main motivation. This may explain why Planks and other core trainings are the most popular workouts.

02 Lack of motivation and guidance are main barriers.

Beyond needing gym equipment, respondents expressed lack of motivation (32%) and lack of guidance (19%) as reasons not to work out at home.

03 People seek guidance and feedback from personal trainers.

Most respondents (80%)  want a personal trainer to "provide feedback" (40%) and "tell me what to do" (31%). The biggest concern is "not sure if I am doing it right" (41%).

04 Over half of the people use fitness apps to help with their workout routines.

55% of the respondents use at least one fitness app. People mainly use fitness apps to track workout time and result, watch tutorials, and find recommended exercises.


From these initial survey results, we discovered opportunity areas in the home fitness market and decided to focus on:

  • Planks as the MVP module since there is a large user base.
  • Provide guidance and feedback for beginners to improve the current experience.
  • Think of ways to sustain motivation in order to maintain platform engagement.
Guerrilla User Interview:
What are the current pain points when doing planks?

After defining our scope to providing motivation and feedback for people who wants to start do planks better, we went to nearby gyms to conduct short interviews with potential users. We asked questions around:

  • What's your normal workout routine at home? How do you keep yourself motivated?
  • Do you use any fitness apps? Is there anything you feel could be better?
  • Can you show me how you currently use your fitness app?


These feedback corroborated some of our findings from the initial survey, which allowed us to zoom into some possible design opportunities:

  • Use close-knot social network and gamification to keep the user engaged and accountable.
  • A hands-free and truly human-centered experience can be a key differentiator.
  • There are improvements to be made for following tutorials and receiving feedback.
Competitive Analysis:
What are the current solutions out there?

Since we have decided on several potential differentiators -- utilizing close social network, providing in-time feedback, hands-free experience, we wanted to look at the existing solutions to see if we could gain a competitive advantage in this booming market. We investigated and compared the highest ranked fitness apps in the app store along the following dimensions:


These successful apps each have distinctive selling points -- automatic tracking, personalization, gamification, abundant tutorial, etc. Due to the scope of the project, we cannot replicate some of these aspects. Therefore, we decided to utilize close-knot community as motivation rather than building a public platform, use direct feedback as a main differentiator, and zoom in on the details of the interaction that would make this experience thoughtful and delightful.

Solution Ideation

Expert Interview:
How do trainers currently provide posture feedback?

Since we wanted to provide prompt feedback for novice users as a key differentiator, we first interviewed a fitness trainer to see how he normally adjust people's postures. We went in with a few technological solutions in mind, but focused mostly on the current mechanism to find potential opportunity space.

From this conversation with the trainer, we learned a few things about doing planks effectively:

1/ Holding onto the right position is more important than the length.
2/ It is important to keep the back straight and hips not too high or low.
3/ It is recommended that novices start at 30 seconds and gradually increase.

Regarding the feasibility of using muscle sensors to gauge training effectiveness, the trainer noted that core muscle activation can be taken as a proxy for that, since if the posture wasn't right, the core would not be properly activated. However, if the core is already activated, even if the posture slips later, it would still be tense and show up as activated, at least for a while.

Solution Ideation & Technicality Research:
How might we provide posture feedback via mobile phone?

None of the current apps provide personalized feedback directly, this may be due to the technological limitations. Nevertheless, it presents an interesting challenge to tackle for us. We researched some current sensing technology and brainstormed different ways we can sense the posture as input and provide feedback as output. There are mainly three ways we can potentially do that via sensor:

Although these solutions are conceptually feasible for capturing posture or muscle activation data, none of them is practical, either due to cost or implementation effort.

Substitute Solution:

After investigation, we found that the current sensors are not readily usable for providing posture feedback, so we decided to use another way to provide feedback: videotape their workout session, compare to the tutorial, and customize the feedback for next time.

Prototyping & Testing

Paper Prototype:
What is the logical workflow for the intended tasks?

Based on the main functionalities and tasks defined, I started paper prototyping and discussed the features and workflow with the team. We made a few changes around the combat mode, since multiple users are involved.

Wireframing & User Testing:
Do users find the features useful and the flow natural?

Based on the wireframe, I made an InVision prototype to test with 4 users. In addition, we also did Wizard-of-Oz to see if people can tell what are the improvement areas by video recording and comparing with the tutorial.

User Testing Feedback:

01 Workflow and notification for the combat mode is confusing.

“I didn’t know how to find out about a new battle request. The notification is confusing.”

02 Users worry about privacy issues around video recording.

“I don’t want to publish my videos and make it visible to all friends.”
“ I worry my friends can download my videos.”

03 Voice command and combat with friends are well-received.

“It’s smart to use competition as a way to keep people motivated.”
"Voice command would be so convenient!"

04 Users are able to tell improvement area from video recording.

"My back should have been straight, it sacked after like 30 seconds."

Final Design & Presentation

Hi-Fi Prototype:
What's the look and feel?

We decided to go with a professional look in a dark mode. Here are the interactive prototype with three workflows (registration, exercise mode, combat mode).

We presented this prototype and our poster at the projects fair and won the 2nd place out of 12 teams!

Learning & Reflection

This project has been a unique experience that goes beyond the human-centered design process and allowed me to work with developers directly. Finding the balance between business value, user experience and development effort has been a continuous discussion within our interdisciplinary team. Hence, the iterations were made not only based on user feedback, but also technical and business considerations.

During this project, I have learned ...

  • Design is at the intersection of people, task, and technology
  • How to balance business value, user experience, and development effort
  • How to communicate effectively with a interdisciplinary team

If I have more time, I would ...

  • Design the workflow for combat mode between more than two players
  • Test if the user can improve his/her posture through this way over a period of time
  • Consider ways to expand the capabilities to support other types of exercise