Our Team

Meet the Coaches at Endurance PTC - Mill Valley Fitness Experts

Our coaching team at Endurance PTC is built from a diverse group of fitness professionals, athletes, physical therapists, and cycling specialists who bring unmatched experience and energy to the studio. Based in Mill Valley, CA, we’re united by one goal: helping you reach yours.

Whether you're training for a triathlon, building strength post-injury, or improving your cycling efficiency, our coaches offer science-backed guidance, decades of experience, and a whole lot of heart.

  • Brown and white dog with blue collar on a leash

    FINNEGAN

    Director of treat management, professional urban sled dog, habitual tail wagger, and official greeter.

  • Smiling man in gray cycling jersey with 'Endurance Mill Valley' design on a plain background.

    TIM FLEMING, MSc

    Founder of Endurance PTC, Tim brings 20+ years of coaching experience in endurance training, performance testing, and eCycling. A former pro triathlete with a Master’s in Exercise Science, Tim blends science, sport, and strategy to help athletes of all levels optimize their potential.

  • Man smiling, standing against a textured wall with dappled sunlight.

    JAFFA PRINCE

    A biomechanics expert and elite-level cyclist, Jaffa offers deep insight into cycling technique and triathlon performance. Based in the Bay Area since 2002, he brings a competitive edge and global perspective to performance coaching.

  • Person smiling in front of wooden fence, wearing a light blue "Endurance" t-shirt.

    CAROLINE COBLE

    A seasoned Ironman triathlete and marathoner, Caroline specializes in long-distance training for runners and triathletes. Her coaching is perfect for athletes balancing competition and life - including parenthood.

  • Man adjusting a blue road bike in a bike shop, surrounded by cycling accessories and equipment.

    ANDREW MCWHORTER

    Andrew is a trusted resource for cyclists across Marin County. Whether you're dialing in bike fit or fine-tuning your form, his personalized approach blends technical expertise with hands-on support.

  • Person wearing an "Endurance Mill Valley" cap and white shirt with logos, smiling against a dark background.

    BETH JEFFRIS, MSc

    With a Master’s in Exercise Physiology and 25+ years of personal training, Beth leads our injury-prevention efforts and co-develops our eCycling program. She's passionate about biomechanics, community coaching, and functional fitness.

  • Smiling woman in sports attire with long hair, wearing a dark cycling jersey with logos on it, against a white background.

    HOPE HORTON

    Hope blends decades of road cycling experience with 20+ years in sports medicine. Her classes emphasize form, safety, and long-term strength—perfect for anyone recovering from injury or new to endurance sport.

Personal Trainers

  • Older man smiling, wearing 'Endurance Mill Valley' t-shirt, with shadows on his face.

    CHARLES WALZ

    With over 25 years as a health and fitness specialist in Marin County, Charles is known for his warm, intuitive approach. Each session begins with, “How do you feel today?”—allowing him to tailor workouts on the spot. Charles blends cardio, strength, and flexibility training to create effective, personalized routines.

    Certifications:

    ACSM Advanced Personal Training

    Exercise for Older Adults

    Spinning & TRX Instructor

    Contact
  • Smiling woman in a black tank top in front of a dark background.

    CHRISTINE WALDRON

    Christine is a licensed orthopedic physical therapist turned personal trainer with a passion for functional strength training and injury prevention. Her thoughtful programs are ideal for those navigating physical limitations while working toward sustainable strength and mobility.

    Specialties:

    Post-rehab strength

    Trail running

    Functional movement for long-term wellness

    Contact
  • A woman smiling next to a small dog sitting in a stroller, outdoors on a sunny day.

    KELLI ROBINSON

    A former collegiate and pro soccer player, Kelli is a powerhouse of experience and curiosity. She has completed 25+ continuing education programs and holds certifications in everything from youth fitness to sports psychology. Her energetic, holistic coaching style blends fun with functional science.

    Certifications:

    BS Exercise Science (Biomechanics)

    BA Sports Psychology

    National Strength Coach Certification

    Certified Youth Fitness Specialist

    Certified Speed & Agility Coach

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  • Man smiling in a green shirt outdoors with sunlight filtering through leaves.

    MARK ZEEMAN

    Mark’s experience spans military training, competitive athletics, and two decades of fitness coaching in Mill Valley. A veteran of the South African Defense Forces and ISSA-certified trainer, he helps clients of all ages achieve lasting transformation—whether they’re elite athletes or new to fitness.

    Philosophy:
    “Health is not about the weight you lose but about the life you gain.”

    Contact