Lose weight, gain energy, improve your strength,boost your confidence and have fun doing it.This is Muscle Theory.

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What to expect

Intense Exercise

Training sessions are partnered, grouped or team oriented, competitive, fun, and supportive guaranteeing optimal fitness results. Small private group training with workouts that change daily based on the focus (Cardio 360, Upper Body, Lower Body, Full Body and Conditioning) and is designed to evolve and progress to avoid plateaus. No two training sessions are exactly alike. Polar heart rate monitors are used during all training sessions to help our members track calories, be accountable, lose weight, improve fitness and stay healthy while safely working out. With a Polar heart rate monitor, each member will know which training zone they are in shown on a large tv monitors in the studio. We strive to help individuals improve their mental and physical health.

Founder, Director of Training

Coach Krystal Dattilo

“If it doesn't challenge you, it doesn't change you!”

Raised in the San Fernando Valley, Krystal’s love for sports and athletics started at an early age. She was a year round competitive club soccer, travel softball player for fourteen years. Collegiately played offensive halfback at Holy Names University in Oakland, Ca. She continued her passion for fitness in 2012 by earning her certification as a personal trainer by NESTA. Over the years she has competed in NPC Bikini Competitions and the WBFF where she earned her Pro Card in the fitness category. The team environments and extreme level of physical and mental conditioning Krystal achieved during her formative years ultimately shaped her vision for Muscle Theory.












5:00am8:00am9:30am6:00 pm (Strength & Skills)



Reserve now through the Mindbody app/website. Due to current circumstances, we are no longer offering memberships. Classes are $15/class.

Free Day passes are no longer available*

Hi my name is Jennifer and I've been a member of Muscle Theory since November 2016. I've come along way since joining this gym and honestly wouldn't have been able to achieve my goals without my trainers Krystal and Rennie. I started out a little skeptical cause I had never done weight lifting, cardio, etc. I never thought I would have stayed this long doing the circuits that can be pretty intense at times. But, I've become addicted to going 5 days a week because I've achieved my goals and have lost 12 pounds and 2 inches off my waist. I've learned that working out and eating are all mental and once you achieve that then your results are your reward. I have come to love my body all over again and I couldn't do it without Krystal and Rennie. These are the two most motivational, kindhearted people that make going to the gym enjoyable. They will help answer all your questions and concerns and will guide you through every work out on a daily basis.!

Jennifer Carmona

My name is Marina and I am a proud 1 year member of Muscle Theory. I am so lucky to be a part of this gym-fam. where everyone is so helpful & sweet, and Krystal (owner/ coach) is the icing on the cake! She starts and ends classes promptly, always there to assist and guide us through exercises. Very approachable before & after classes for additional fitness advice. Classes consist of both high & low intensity work outs, toning both upper & lower body. These classes help you build muscle, get stronger & loose weight which I have done since last September. Krystal does two 30-day challenges in a year, plus lots more weekend challenges. I have trained hard and completed both challenges & have lost a total of 29 lbs in the last year at Muscle Theory. I'm so grateful for her coaching efforts!! I look forward to my daily morning ritual walking into Muscle Theory, as Krystal always has motivational messages up, a great attitude of "you can get to your goals, and I will help you"! !

Marina Petrosyan!

Contact Us

Got questions? We want to hear from you!
Please reach us at:



Single Class



15235 Brand Blvd A108

Mission Hills, CA 91345

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