Building an interval timer for Flex Fitness

Learning on the go at General Assembly’s 2016 hackathon

Fitness apps do interval training; even an iPhone has a basic stopwatch. But for the General Assembly Hackathon on March 19th, 2016, our team wanted to get back to the basics and build an interval timer for athletes.

Cyclists, runners, TRX’ers, and gym circuit trainers alike all have a need for a simplistic interval timer, despite the plethora of fitness apps already on the market.

User Research

For our hackathon project, we immediately called Flex Fitness in Oakland, CA and spoke with a trainer named Nicole. She was happy to talk and told us how their circuit-style workouts need a better timing system.

The gym currently has a timer go off every 1 minute by hooking up a laptop on the front-desk to the overhead speakers. When the timer goes off, gym members need to “switch stations” to do a new workout:Pain: Trainers commonly know there

  • Pain: Trainers commonly know there needs to be a few seconds between sets to allow time to people to switch stations
  • Pain: Flex uses a computer plugged into speaker system and use an audio timer
  • Pain: People will burn a full minute because they miss the transition
  • Does any clientele use timer apps? “Not too many, but we recommend the Gymboss app. If they ask, we recommend it for client’s workout. You can make your own timer, set it for infinite rounds.”
  • How many people wear earbuds while working? “40 to 50% — would be higher, but we have music. Earbuds can be a hindrance for non-cardio.”
  • How many use apps while working out? “Maybe 15%… it’s low. Mainly trainers and interval trainers use apps.”

Problem Statement

Flex Fitness in Oakland, CA needs a better timer for interval training. The current timer dings every 1 minute, but doesn’t have a rest or transition period built in, causing athletes to miss intervals or rest for a full minute before starting the next workout.

MVP Ideation + Whiteboarding


Our goal was to design a mobile-first, responsive web app. We used Adobe to produce our wireframes.


In six hours, I joined a five-person hackathon team and built an interval timer for gym interval training:

  • Final product (MVP hosted on Bitballoon)
  • GitHub repository
  • We hit our 4:30pm deadline and were the only group (1 of 10) to launch our MVP product online
  • I built the HTML and CSS from scratch to convert wireframes into a responsive website

Instead of just creating an interval timer, we launched a timer customized for an actual business, Flex Fitness in Oakland, CA, based on their immediate needs.

Our timer enables better workouts for Flex Fitness (circuit gym) users by introducing a transition period between intervals:

  • Stress-free transitions for athletes
  • More intense sprints
  • Easy On-Off toggling for gym staff

Thanks for checking out our project! View more on my portfolio at