Endurance Performance Coaching, Sports Nutrition and Bike Fitting Designed to Help You Perform at Your Best

Helping athletes Become Stronger, Healthier,
and More Resilient.

Coaching and Sports Nutrition Consulting Backed by Experience and Science

Most coaches focus only on training.
Most dietitians focus only on nutrition.
Most bike fitters focus only on the bike.

At Trimarni, we do it all.

With more than 20 years of endurance racing experience and professional expertise, we take a fully integrated approach to performance, combining coaching, fueling, and bike optimization to help athletes train smarter, perform stronger, and race with confidence.

Our
Services

  • Sports Nutrition

    Sports Nutrition

    Fuel for performance, health and recovery.

  • Bike Fit and Optimization

    Precision fitting for comfort, power, and efficiency.

  • Training Plans

    Strategic programming for your next starting line.

  • Green Building icon

    Coaching

    Coaching tailored to your goals and lifestyle.

  • Training Camp

    Train smarter alongside expert coaching.

Train Smarter. Fuel Better. Perform Stronger.

Let us help you improve your Athletic performance

At Trimarni we combine structured coaching, bike fitting and personalized nutrition to help endurance athletes:

● Improve performance without burnout and minimizing risk for injury

● Nourish the body and fuel properly for training and racing

● Build strength, endurance, and resilience

● Stay healthy while stretching the comfort zone

● Optimize cycling aerodynamics, comfort, speed and power

Our
Team

  • Marni Sumbal MS, RD, CSSD, LD/N

    Owner and founder of Trimarni

    Board Certified Sport Dietitian
    Master of Science in Exercise Physiology
    Owner of Trimarni Coaching and Nutrition.

    3x Author
    22x Ironman finisher, 3x XTRI finisher

    6x Ironman World Championship finisher.

  • Karel Sumbal

    Co-owner

    Born and raised in Czech Republic. Category 1 cyclist turned endurance triathlete (who loves to mountain bike) with over 25 years’ experience as a skilled bike mechanic and five years as the GM of the Trek Bicycle Store of Jacksonville, FL. RETUL bike fit specialist, bike mechanic extraordinaire and loves good coffee, croissants and chocolate. 18 x Ironman finisher, 5x Ironman World Championship finisher, 3x XTRI finisher.

  • Joe Nagy

    Assistant Coach

    Ironman Certified
    3x 70.3 World Championship Qualified (2021, 2025, 2026)
    2024 Richmond Marathon - 2:53:09
    2x Boston Marathon Qualified (2025 and 2026)

  • Sunny

    Certified Therapy Dog

What Our Athletes Say

  • Sprint Triathlon

    "I wanted to thank you for your guidance. I did a sprint tri and finished with a PR (for any race of that distance). The high fructose fuel was great for the bike! I entered in the Athena division and won that, but more exciting was that had I entered in the age group, I would have come in first by six minutes. With appreciation for helping me see my body as an ally rather than an adversary. "

  • 70.3 Triathlon

    “Race wins - 1. I stopped halfway through the bike and refilled my bottles with water and the Tailwind I brought along 2. Mentally stayed in the game 3. Didn’t poop in my pants or throw up! I liked the liquid nutrition. If I had relied on solids, I would not have gotten in what I did! And I loved NOT having GI problems!”

  • Marathon

    “I give myself a gold star for executing the nutrition plan. I was able to stay on track which I am sure is why I ran well. I also feel like I was good with the carb loading and drinking Skratch in the days before the race. You’ve been such a big help I’m hoping you have some more wisdom to lay on me for my next race.”

  • Ironman Triathlon

    “I wanted to thank you for helping me on my race nutrition journey for IM Wisconsin. I made it through 6 bottles (in just under 6 hours) of the Infinit fructose fuel (90) on the bike didn’t need anything else. I picked up the second 3 bottles at special needs (totally worth the 45 second stop despite pressure not to stop). I carried Infinit hydration with me on the run. I had extra powder with me to refill an extra bottle and extra powder in special needs. And had 4? Gels to get me through the run. I felt well fueled for the whole marathon with no stomach issues. I was able to hold even splits without slowing at the end. Based on monthly timing which seems to affect me (the week before my period) it was not a race where I felt incredible. But solid training and nutrition got me through. I won my age group (fastest bike and run), 8th female and got a spot to Kona. I think I could have been a bit faster on a different day but I guess that is why I’m not done with this sport yet.”

  • Body Image

    “I feel like I have a generally positive body image and overall positive outlook on things. But it can still be hard sometimes to tone out the brain washing that occurs with how athletes should "look" in order to be fit and fast. I want to thank you for all of the work you do promoting healthy body image, healthy eating and fueling and just healthy bodies in general. I was able to recognize what was happening inside of me, and neutralize those thoughts with was is true: I am more fit now than I have ever been, I am strong, my body is incredible and I am so grateful for what it allows me to do. ...So thank you!!”

  • Bike Fit

    “I wanted to give you a quick feedback from last weekend. I participated at IM70.3 Chattanooga. 2nd race with my new QR bike; 1st big race. It was great. I think, and this is not overestimated, I overtook approximately 200 people on the bike. I felt very comfortable. Stayed on the aero bars all the time (except of some curves); and stayed on the front tip of my saddle with my butt. Didn’t feel weird and had no pain at all! I wanted to thank you for your support and the bike fitting. Great job with your analysis. I’m very excited for IM Chattanooga!”

  • Triathlon Camp

    “The Trimarni Greenville camp challenged and grew me in many ways. I specifically remember being placed in a group with some athletes who I knew were stronger than me for a long ride. I felt I was out of my league and talked to Marni about my doubts. She reassured me that I was strong and they had placed me in that group because they knew I could handle it. Yes, I worked hard (very hard!) on that ride- but it was so worth it. I learned that I am stronger than I sometimes give myself credit for - and that joy you feel after accomplishing something you thought you couldn't is hard to beat! There were many moments like this during this camp - having doubts, pushing just a little harder, and then finding success on the other side. I wouldn't have had these moments of success if it wasn't for the amazingly supporting group Marni and Karel bring to these camps, and of course for the wise coaching eyes of Marni, Karel, and Joe. If you're looking to push yourself outside your comfort zone in a supportive and informed environment- TriMarni camps are the way to go! “

  • Triathlon Camp

    “After being in triathlon for 10 years I attended my first TriMarni camp in 2018 (and have attended many camps since then).  At every camp I learn more about climbing and descending techniques in very different terrain from where I was currently training.  This has allowed me to challenge myself along with preparing me for very technical mountainous courses like the Ironman World Championship in Nice, France.  These camps provide individualized attention for each sport (swim, bike, and run) as the groups are small with multiple coaches providing feedback.”

  • Triathlon Camp

    “Attending a Trimarni camp was one of the best decisions I have made as a triathlete.  In 2017 I went with a friend to camp and had no idea what to expect.  I was not a Trimarni athlete (yet) and was worried that I would not be able to keep up.  I was so impressed with how the workouts were organized to make sure that they were challenging for everyone.  On all of the bike workouts the coaches were right there biking with you.  They gave pointers for shifting, climbing, and descending that you could practice right away.  In 2021 I returned for another camp as a Trimarni athlete to get ready for Ironman Lake Placid.  It was so nice to do the workouts with the support of the coaches, team, and SAG support.  Again they gave individual attention to every athlete and I learned so much especially on the bike.  I think that the bike workouts I did in Greenville at camp have prepared me for any Ironman bike course.  I have so much more confidence going into my training and racing knowing that I was able to finish the rides at camp and I can still hear the coaches telling me to shift.  I recommend the Trimarni camps to any triathlete looking to learn and train in a positive group environment.”

  • Speaking/Presentation

    “I want to thank you again for sharing yesterday some valuable information. You are a wealth of knowledge! If you ever want to speak again we would LOVE to have you!”