Meet Our Coaches

We want to take a moment to write about the Crossfit Proven coaching staff. We believe that coaching is critical to your experience and is something that differentiates Proven.  Anyone can become a Crossfit coach by meeting all the requirements of a Level 1 Certification seminar.  That certificate is only the foundation for our coaches at Proven.  We strive to hold our coaches to a higher standard. Each member of the staff is chosen for their ability to engage with athletes of all levels, their ability to teach athletes to perform movements safely, their enthusiasm for building the Proven community, and their passion for learning and building their own technical expertise.

     Each of our Coaches have come up through the ranks as members of CrossFit Proven.  Most of our coaches have been learning exclusively from at Proven for 1 to 3 years.  They’ve become proficient in our exclusive techniques that have brought success to all of our athletes.  This experience is invaluable and is the key ingredient in the application of our coaching techniques.  Our coaches engage in continuing education through regular clinics at CrossFit Proven.  These clinics focus on the development of their technical expertise.  Each coach goes through an inclusive and intensive apprenticeship under the direct tutelage of Matt and each have demonstrated a complete proficiency and efficacy as a coach before they are able to lead classes at CrossFit Proven.  Our coaching staff also participates in seminars and receives certifications outside of Proven’s in-house program like;  CrossFit’s Olympic Lifting Certification and CrossFit Mobility.  

     Our staff has a commitment to excellence and constant learning.  Proven coaches will always put the needs of Proven athletes first when we are at the box.  We know that one thing you ask of us and the other coaches is to give you the best effort we have everyday and ensure you have the best experience possible.  We pledge to you, our members and our staff, that we will strive everyday to deliver that best possible experience. Exceptionalism is our standard.  Below, you can read brief bios on each of the Proven coaches.  

Thank you for making Proven the best place to be a coach.


  • Matt Chambers

    Founder, Matthew Chambers has 20+ years experience working as a professional Strength and Conditioning Coach. Professional athletes, homemakers, seniors and children alike have seen great success working with Matt; and you will too! Coach Matt has developed hundreds of coaches all over the world working as an instructor at the National Personal Training Institute since 2007. Matt has been the Head Coach at a successful CrossFit for over seven years in which he has taken teams to the “Reebok CrossFit Games Regional” four times and has taken a “Masters Level” athlete to the “2011 Reebok CrossFit Games”. When Matt isn't coaching he spends time with his family, whom you will also find at the box on a regular basis!

    CrossFit Level 1 Trainer



  • Brittany Yilmaz-Chambers

    Co-Owner, Brittany Yilmaz-Chambers has always had a passion for community and connecting with others. Pursuing this passion first through volunteer work, then yoga and cross training during her college career, and later professionally as a social worker, Britt discovered that she could also fulfill that passion in CrossFit. CrossFit quickly captured Britt's heart and she attained her CrossFit Level 1 Trainer certificate one year after starting CrossFit. Britt strives to share all aspects of CrossFit with those she encounters in hopes of helping members achieve their goals and find the fulfillment offered in CrossFit. With a dedication to holistic healing, clean eating and connecting with the power of God and self, Britt believes fitness is much more than exercise.  When Britt's not coaching, you can find her working with her nutrition clients, training and spending time with her family and friends. 


    CrossFit Level 1 Trainer


    Eat To Perform Certified Nutrition Advisor

  • Mike King

      After years of destroying his knees playing basketball and volleyball Mike King was inspired to try CrossFit in April of 2010. He hasn't looked back since and now you can find the entire King family at the box. Mike received his Level 1 Trainer Certificate in September if 2012 and his Olympic Lifting Certificate in November 2013. Outside of the box Mike is first and foremost a husband to Mindy and a father to Daniel and Hannah. He makes his living as a Six Sigma Master Black Belt/Manager at Vanguard. Mike's goals as a coach are to ensure Proven athletes have fun (safely), achieve their goals, and embody the CrossFit spirit of virtuosity. Ask him about that.


    CrossFit Level 1 Trainer

    CrossFit Olympic Lifting Trainer

  • Mike Johnson

    Mike has always been active in sports and recreation; from baseball to football and long distance backpacking since the age of 7. He signed himself up (as well as his wife, without her knowledge) at Proven the day after returning home from his honeymoon in June of 2012 and hasn’t slowed down since. The decision to coach at Proven was easy as he gained great knowledge and respect from the sport of CrossFit and sharing that with others is very rewarding to him. A graduate from the University of Pittsburgh, Mike is an accountant by day, and lives in Exton with his wife, Teri. They are expecting their first child this June.

    CrossFit Level 1 Trainer

  • Chris Lebresco

    Chris is one of many CrossFit Proven success stories. Back in April of 2013, Chris came to Proven overweight and out of shape. After only 8 months of dedication to CrossFit along with a healthy diet, Chris was able to shed 50lbs and become stronger and healthier than ever before. During this transformation, Chris’ passion for CrossFit grew and now as a coach he is looking to help others reach their fitness goals.

    Chris enjoys staying active by running, biking and swimming and frequently competes locally in 5k runs, bike races, triathlons and CrossFit competitions. He also plays basketball, deck hockey and tennis whenever he gets a chance.

    Chris’ goal as a CrossFit Trainer is to help CrossFit Proven members take their athletic abilities to the next level and to see members constantly improving.

    When Chris isn’t coaching or working out, you can find him taking care of his two children Nick and Brooke and trying to keep up with his CrossFit wife, Lindsay. You may also run into Chris out at your favorite bar or restaurant where he regularly performs as a solo acoustic act throughout the Philadelphia area.

    CrossFit Level 1 Trainer

  • Brian Parks

    Brian has been passionate about fitness for over 30 years, including gym memberships, running, adventure racing, golf and other outdoor activities. He is also an avid woodworker and gardener. He found CrossFit through friends in 2011 and was instantly addicted to the workouts, the atmosphere and the community. Brian has a passion for teaching others and is motivated by helping other athletes excel at all aspects of CrossFit. When not at the box, Brian enjoys spending time with his family and can be found watching his daughters compete in equestrian events and field hockey. 


  • Derek Wakefoose


    Head Coach, Derek’s athletic career began at age 10 with soccer and baseball. Within the year, he realized he held a passion for all athletics. Over the next few years Derek participated in soccer, wrestling, lacrosse, baseball, and football, excelling in anything to which he commits. In 2008, Derek began his CrossFit and Olympic lifting journey. He devoted all of his time and energy into developing his gymnastics and Olympic lifting. In the following years, Derek qualified two times for junior nationals in Olympic lifting. At 18, he received his CrossFit Level 1 Certification and immediately began assistant coaching. Since 2014, Derek has been coaching in both group and personal settings. Eight years of personal experience, combined with an extensive athletic background, has allowed Derek to help many people of all ages. With Derek’s help, these people have been able to find success in their health and fitness goals. Outside of the gym you can find Derek climbing trees, reading, learning and spending time with friends. His passion and positive energy brings a welcome addition to the CrossFit Proven staff. 

    CF-L1 Trainer 

  • Brie Sfamurri

    Brie has been involved in weightlifting since 2015. She has competed at the national level multiple times, including the American Open and the American Open Series II, where she took silver overall. Brie provides her coaching to many other local gyms and loves the opportunity to help lifters, new and old, dial in technique and achieve their goals.  Brie will be coaching the Tuesday and Thursday classes at 5:15 PM!

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