As race participation surges, the new AI-powered coaching app offers in-workout guidance based on pace, heart rate and performance data, taking on established platforms like Runna
The running boom isn’t just about hopping into group runs or joining the hundreds of run clubs out there. Now, people are looking to race.
According to Strava’s 2025 “Year in Sport” report, participation in races increased significantly, with Gen Z leading the charge with year-over-year increases of 28% in 5Ks, 39% in 10Ks, 31% in half marathons and 33% in full marathons.
But arguably the most important component of that race participation isn’t simply signing up, it’s committing to training.
That’s where AI running coaches come in, as beginners and experienced runners look for support through training. While market leader Runna has seen monstrous growth and was acquired by Strava last year, it could have serious competition with the recent launch of a new coaching app, Kasi.
Kasi is an AI-powered coaching platform that offers real-time feedback and guidance during workouts, entering the ears of runners to give them guidance while they’re running.
“For years I thought, ‘I wish I could just be at my runner’s workouts, when they’re doing the workouts, because I would love to be able to coach them in person in real-time.’ And that’s what gave me the idea for this,” Kasi founder and CEO Dr. Jason Karp told Athletech News.
Having A Coach in Your Ear
To get started, users enter in a recent race time of any distance — whether it’s from a 5K or half marathon — then the app will calculate what pace to run for each type of workout, from easy everyday runs to lactate threshold workouts and speed intervals.
“I’ve been coaching runners for a long time, and unfortunately, runners often do their workouts incorrectly,” Karp explained.
“The big gap is that right now, online coaching is all passive,” he added. “You write the training schedule, you send it to the runner, they do the workouts, and then they report back to the coach.”
While the program will apply machine learning as it pulls from a larger library of runners, the app is currently built from “if/then” statements applied from Karp’s own training theory, entering runners’ workouts based on how he would coach in certain scenarios, like running too fast for the first interval of a speed session, utilizing data such as pace, heart rate and ground contact time.
Once the app knows what paces you should roughly be running, the AI coach will talk through your headphones to let you know if you’re on the right track, or if you need to slow down, based on pace and/or heart rate.
Karp said that if a runner starts a workout too fast, the app might even tell them to stop and start over, while explaining the purpose of the workout and why it’s important not to overdo it.
“I think that’s the big reason why runners don’t do their workouts correctly: because they don’t deeply understand what it is that they’re trying to accomplish in their workout. So it’s helpful if you have a knowledgeable coach right there with you,” he explained.
Keeping Space for Human Coaches
But it’s not only AI-powered — Karp’s app also provides real-life coaches the opportunity to offer intra-workout feedback, transmitting data to a coach using the Kasi platform and allowing them to observe the workout and communicate with the athlete in real time.
“Online coaching is so popular, yet the coaches can’t physically be at their athletes’ workouts,” Karp said. “So my app gives them a way to be able to do that and coach them while they’re doing a workout.”
Karp recognized that Runna is his biggest competitor, but he thinks that the expertise he brings into the app as an experienced and credentialed coach, as well as the platform he’s providing other coaches, creates a better product overall, rather than relying solely on AI.
“When it’s done right, coaching is teaching, and oftentimes that teaching has to take place in the moment while the athlete is doing the workout,” he said. “That’s the best time to teach.”
The app is currently available on the App Store as RunKasi, and syncs with the Apple Watch and iPhones, but Karp is hoping to get it integrated with other common running watches like Garmin.
