Our Story
Built on
Decades of Discipline.
The Beginning
From martial arts to modern fitness.
HIIT AF is a kickbox and strength HIIT studio at 8160 Haven Avenue in Rancho Cucamonga, California. We run 45-minute classes built around 10 stations of boxing, kickboxing, and full-body strength training, with a trainer on the floor for every session. Your first class is free.
HIIT AF was born from a simple idea: take the discipline and intensity of martial arts training and make it accessible to everyone. Founded by Steven Liu — a martial artist with 40 years of Tae Kwon Do experience — the studio blends boxing, kickboxing, and full-body strength training into a 45-minute circuit that challenges your body and sharpens your mind.
After operating Kickbox Fitness gyms from 2015 to 2025, Steven refined the format into what HIIT AF is today: 10 rotating stations, daily program changes, and a trainer on the floor guiding you through every rep. That ten-year operator background is the difference — most boutique HIIT studios are franchises running a national program. HIIT AF runs Steven's program, refined inside his own gyms over a decade with thousands of members.
Located in Rancho Cucamonga and serving the western Inland Empire — Upland, Ontario, Fontana, Eastvale, and everywhere in between — HIIT AF welcomes athletes of all levels. First-timers, returning lifters, seasoned fighters, and kids in the small-group kickbox program all train under the same roof. The environment is built on encouragement, intensity, and results: member Gina R. lost over 60 pounds; member Victoria H. went from never setting foot in a gym to training six days a week.
What We Stand For
Our Values.
Intensity
Every session pushes your limits. 45 minutes of focused, high-output training that delivers real results.
Accessibility
No experience needed. Our trainers meet you where you are and guide you through every movement.
Variety
A new program every single day. You'll never plateau because you'll never do the same workout twice.
Community
Train alongside people who motivate you. HIIT AF is more than a gym—it's a team that shows up for each other.
Come see for yourself.
Your first class is free. No commitment, no pressure—just 45 minutes of work.