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Personal training in Santa Clarita built around a structured system
Build muscle, move better, and stay strong for life with the Longevity Strength System at CozmoSize Fitness in Newhall.
Personal training for adults who want real progress—stronger lifts, better conditioning, and a program that fits their lifestyle and actually sticks.
Stay active. Feel confident. Keep doing what you love.
Start your journey with a structured plan.
Personal training in Santa Clarita for adults who want structured, long-term results
A structured strength system designed to help adults build muscle, reduce body fat, move better, and feel confident in their body—without burnout, confusion, or extreme workouts.
Most gyms leave you guessing—jumping from workout to workout with no real direction. The Longevity Strength System follows a structured progression, where every phase builds on the last. Your strength improves, your body changes, and your results actually last.
This system is designed to help you build lean muscle that supports fat loss, increase strength so everyday life feels easier, improve energy, movement, and joint health, and feel more confident in how you look and feel.
You won't be thrown into workouts that don't fit you. Every member trains inside the system—but with exercises adjusted to your level, guided coaching every session, and progressions that match your ability. Challenged, never overwhelmed.
You don't need extreme workouts to get results. You need a system you can stick to. Whether you train 2–5 days per week, the program fits your schedule, supports recovery, and keeps you progressing long-term.
You don't just work out—you change how your body performs.
This isn't just training. This is a system built to evolve with you—and last.
Semi-private training built around the Longevity Strength System—designed to help you build strength, reduce body fat, and stay consistent for the long term.
This is how training is meant to be done. You'll train in a semi-private environment, but your program is fully personalized, structured, and built around your progress inside the Longevity Strength System. No random workouts. No guesswork. Just a clear path forward.
More access. Better results. Train consistently with a system designed to fit your life—so you can build momentum, stay accountable, and actually see progress. This is coaching built for real life, not something you start and stop.
Built for adults who want to:
Book your free consultation and see if semi-private coaching is the right fit for you.
Book Your Free Consultation →Personal training in Santa Clarita serving Newhall, Valencia, Canyon Country, and Saugus.
Most people don't need more workouts. They need better training—structured, progressive, and built to last. Because the goal isn't just to look better for a season—it's to build strength, confidence, and a body that supports your life long term.
To stay active as you age. To keep doing what you love. To feel capable, independent, and in control of your life.
Because when your body is strong, you have the ability to show up fully in your life—and leave your mark.
Meet Matthew Cather
Founder of CozmoSize Fitness · Creator of the Longevity Strength System
Matthew Cather founded CozmoSize Fitness to bring a higher standard of training to everyday adults—built on the same principles used in real strength and conditioning programs. With over 20 years of full-time, hands-on coaching experience, he has worked with hundreds of individuals, from beginners to experienced lifters, helping them build strength, improve their bodies, and stay consistent long term.
His approach was shaped during his time playing football at College of the Canyons, where he was introduced to structured, progressive strength and conditioning under elite-level coaching. That experience changed everything—for the first time, training wasn't random. It was planned, intentional, and built to produce measurable results over time.
After years of coaching and seeing the gaps in the fitness industry (random workouts, inconsistent programming, short-term approaches), Matthew developed the Longevity Strength System: a structured, strength-first system designed to help adults build muscle, reduce body fat, move better, and stay consistent for the long term.
Today, CozmoSize Fitness in Newhall serves adults across Santa Clarita, Valencia, Canyon Country, and Saugus through a semi-private coaching model—delivering personalized training within a proven system.
Also NSPA Certified Weightlifting Coach, Certified Sports Nutrition Coach, and Certified Speed & Agility Coach. Mentored under Master Strength Coach Robert dos Remedios. Finished top of class in the NSPA live coaching evaluation.
Featured by VoyageLA for building one of Santa Clarita's standout coaching communities → Book Your Free Consultation →Getting started is simple. We guide you every step of the way.
A quick, no-pressure conversation to learn about your goals, your starting point, and what you want to achieve—while making sure CozmoSize is the right fit for you.
A deeper look at where you are and where you want to go. Includes an InBody composition scan, a movement screening, and a clear game plan using the Longevity Strength System.
Step into semi-private coaching and begin following a structured plan designed to help you build strength, stay consistent, and finally see the progress you've been looking for.
See how adults across Santa Clarita are building strength, staying consistent, and feeling more confident with the Longevity Strength System.
★★★★★"I've been working out here for about two months and have absolutely seen results. The program is planned out daily and approachable."— D.C. · Santa Clarita
★★★★★"So much care, effort, and knowledge goes into each week's cycle of workouts."— Jessica G. · Santa Clarita
★★★★★"Matt and the rest of the trainers are incredibly knowledgeable and supportive. I've seen amazing results and actually enjoy showing up to train."— Parker J.
★★★★★"I have little to no experience with resistance training and already feel hooked."— Caroline A.
★★★★★"Best gym ever! I've been working out with Matt for over ten years and it continues to be challenging."— Jennifer M. · Valencia
★★★★★"The vibe is all-inclusive. There are people in their 20s through 60s, and everyone is supported and challenged at their own level."— Lisa A. · Santa Clarita
This isn't a crowded gym or a follow-along class. Every session is structured. Every movement is coached. Every client is progressing through a system designed for long-term results.
From beginners to experienced lifters, every client trains within the same system—adapted to their level, their goals, and their lifestyle. Because results don't come from intensity alone. They come from structure, consistency, and an environment designed to help you succeed.
Semi-private personal training combines individualized coaching with the structure of a small group. Each workout is personalized using detailed movement assessments—so you train based on your fitness level, goals, and movement quality. Through the Longevity Strength System, your training is designed to fit into your life, helping you move better, get stronger, and stay consistent over time. Every session is guided, structured, and tailored to you—so you get the benefits of personal training within a supportive, coach-led environment.
Absolutely. We work with adults of all experience levels, including those who are brand new to strength training. Your program is built around your starting point, and every exercise is adjusted to match your ability. You'll be coached every step of the way—so you never feel lost or overwhelmed.
Each session is approximately one hour and follows a structured plan within the Longevity Strength System. You'll move through a guided warm-up, a strength or conditioning block with real-time coaching, and a metabolic finisher. Every session is part of a larger progression—nothing is random.
Start by booking a free discovery call. We'll talk through your goals, training history, and schedule, then guide you through the next steps, including your in-person consultation. No pressure. Just a clear starting point.
No. All memberships are month-to-month. However, real results take time, and we recommend committing to the process for at least 3–6 months to fully experience the benefits of the Longevity Strength System. We focus on delivering results and a great experience—so clients stay because it works.
We offer coaching sessions Monday through Friday. Morning: 6:00 AM – 11:00 AM. Evening: 4:30 PM – 7:00 PM. During your consultation, we'll help you find training times that fit your schedule and routine.
A quick, no-pressure consultation to map out your goals and see if CozmoSize is the right fit.
📍 24727 Railroad Ave, Newhall, CA 91321
🕐 Mon–Fri · 6:00–11:00 AM & 4:30–7:00 PM
