Meet the Team


Fathom's coaches are a full-time professional staff (no hobbyists here). These men and women have earned the highest levels of education, and have obtained unique, real world training experiences. Our coaches are passionate about using their expansive experience to help YOU crush your goals no matter if you’re a beginner, an adaptive athlete, or an experienced CrossFitter.
  • Alec Zirkenbach

    Owner and Coach

    “Zirk” is passionate about, and specializes in, adaptive and wounded warrior training. Veteran fitness and long-term health are deep-rooted passions for Alec; a disabled veteran himself. After college, Alec was commissioned in the U.S. Navy and was deployed to combat zones multiple times and served on numerous counter-piracy operations. He suffered a tragic injury that left him hospitalized for months and required 10+ surgeries to try and save his leg. Rehab and recovery were a slow and demoralizing process for him … until he rejoined CrossFit.

    Despite losing function and sensation in his right leg, Alec returned to active-duty service for two more years. During his last tour he co-founded Kuwait Naval Base CrossFit (a military affiliate) and is now the current Owner/Operator of Fathom as well as the Founder and Head Coach for the Fathom Adaptive CrossFit Program which serves all adaptive, wounded, ill, and injured athletes in Southern California.

    “CrossFit, and more specifically, the amazing people in this empowering community, literally got me back on my feet,” Alec says. “Today, I’m stronger and healthier (albeit disabled) than I have ever been, and I would never be where I am today if it weren’t for CrossFit. I train, coach and love CrossFit because it gave me a second chance at a healthy and happy life.”


    • USA Weightlifting Sport Performance Coach
    • CrossFit Level 3 Trainer
    • CrossFit Adaptive Training Seminar Staff
    • CrossFit Olympic Weightlifting Trainer
    • CrossFit Gymnastics Trainer
    • CrossFit Movement & Mobility Trainer
    • CrossFit Powerlifting Trainer
    • CrossFit Kettlebell Trainer
    • CrossFit Aerobic Capacity Trainer
    • CrossFit Defense Athlete Trainer
    • Catalyst Athletics Certified Weightlifting Coach
    • Fascial Movement Taping (FMT) Levels 1 & 2
    • Adult and Child CPR/AED/First Aid
  • Marissa McGuirk

    Head Coach

    “Mo” studied human movement and earned her Kinesiology Master’s Degree with the specific goal of making a career of helping people achieve their fitness and performance goals. She is passionate about improving mechanics and technique, and you’ll often find her helping athletes achieve a new skill.

    Armed with advanced degrees, a lifetime of continued education and certifications, “Coach “Mo” serves our athletes as Fathom Head Coach. On top of providing expert coaching, her responsibilities also include assisting in developing Fathom’s top-rated working programming by conducting weekly program analysis, researching best practices, and collecting data from athlete performance. That means more effective and fun training for you!

    “Mo” has been coaching CrossFit for years, and she’s spent many more years coaching strength and conditioning training at the collegiate level and for local SWAT and tactical teams. She is also serves as a movement specialist on Fathom’s Adaptive CrossFit coaching team.


    • Master of Science, Kinesiology
    • Certified Inclusive Fitness Trainer (CIFT), ACSM
    • Certified Strength & Conditioning Specialist (CSCS), NSCA
    • USA Weightlifting Sport Performance Coach
    • Certified Functional Movement Screen Specialist (FMSC)
    • CrossFit Level 3 Trainer
    • CrossFit Kids Trainer
    • CrossFit Movement & Mobility Trainer
    • Certified Trigger Point Performance Therapy Specialist (TPPT)
    • Adult and Child CPR/AED/First Aid
  • Libby Landry

    Director of Corporate Wellness and Coach

    Libby moved from New Orleans, LA, to pursue her master’s degree in public health at San Diego State University. Her philosophy on health and wellness is this: small lifestyle changes create sustainable daily habits. “There’s no one giant step that does it… it’s a lot of little steps.”

    Libby has coached both kids and adults for many years. A highlight of her career was coaching New Orleans Saints Head Coach Sean Payton and CrossFit HQ Staff Member Rory McKernan. She most enjoys getting to know her athletes individually to provide the best coaching cues in a fun atmosphere. When she’s not at Fathom or in school, you can find Libby hiking San Diego’s many trails or surfing at Tourmaline.


    • CrossFit Level 2 Trainer
    • CrossFit Movement & Mobility
    • CrossFit Kids
    • USAW Sport Performance Coach
  • Dan Lucas


    Dan has been coaching CrossFit for more than six years, and specializes in helping members achieve specific goals through personal training. Dan is constantly striving for continued education and to bringing innovative training methods to Fathom. The Doctor of Physical Therapy degree he is currently pursuing allows him deliver a greater understanding of functional human activity to Fathom athletes.


    • CrossFit Level 1 Trainer
    • CrossFit Olympic Weightlifting Trainer
    • Certified Personal Trainer, National Academy of Sports Medicine
    • Adult and Child CPR/AED/First Aid
  • Chase Besuden

    Olympic Weightlifting Coach

    Chase discovered Olympic weightlifting through CrossFit and was immediately hooked. He then went on to train Oly on the UNLV Weightlifting Team while attending Law School. Now, Coach Chase runs Fathom’s USAW sanctioned weightlifting program and is dedicated to helping members of every level achieve their weightlifting goals.

    Come join him for a Olympic weightlifting class today!


    • USA Weightlifting Sport Performance Coach
    • Adult and Child CPR/AED/First Aid


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