At Trimarni Coaching, we believe exceptional coaching begins with understanding the individual. No two athletes are the same. Every athlete brings a unique combination of goals, experience, strengths, challenges, lifestyle demands, and performance aspirations. Our coaching philosophy is built around recognizing those differences and creating a personalized approach that helps each athlete achieve sustainable, meaningful progress.

We coach every athlete as an individual—not as a template. Whether your goal is completing your first triathlon, setting a personal best, qualifying for a World Championship, or simply maintaining a healthy and balanced lifestyle, our programs are designed to fit your life rather than take it over. We believe triathlon should enhance your life, not consume it, and our goal is to help you maximize your performance while maintaining long-term health, enjoyment, and balance.

As coaches and athletes, we bring decades of hands-on endurance sport experience to our athletes. Together, we have completed more than 40 Ironman triathlons and qualified for the Ironman World Championship 10 times. We understand firsthand the physical, mental, and logistical demands of endurance training and racing. More importantly, we know what it takes to prepare athletes of all levels for success, from first-time finishers to highly competitive age-group and professional athletes.

2025 Trimarni Team Results


Marni Sumbal, MS, RD, CSSD, LD/N

Marni is a Board Certified Specialist in Sports Dietetics (CSSD), holds a master of science in exercise physiology, 3x published author, and accomplished endurance athlete. She has held a USAT Coaching certification for almost 20 years. Her athletic achievements include 22 Ironman finishes, 3 XTRI finishes, 6 Ironman World Championship appearances, a 5th-place age-group finish at the 2021 Ironman World Championship in St. George, Overall Female Champion at the 2024 Ironman 70.3 Louisville, and Overall Female Amateur Champion at the 2024 Ironman Chattanooga.

Her expertise uniquely combines exercise science, performance nutrition, and endurance coaching, allowing her to help athletes optimize every aspect of training and racing.

Throughout her coaching career, Marni has guided athletes from their first endurance events to Ironman finishes, age-group podiums, personal best performances, and lifelong health improvements. Her extensive background in sports nutrition has helped countless athletes develop confidence through effective fueling strategies, improved dietary habits, and race-day nutrition plans that support peak physical and mental performance.

Karel Sumbal, RETÜL Bike Fit Specialist

Karel brings a unique blend of cycling expertise, triathlon experience, and technical knowledge to the coaching team. As an experienced RETÜL bike fitter and highly skilled bike mechanic, he helps athletes maximize efficiency, comfort, and performance on the bike.

A former Category 1 cyclist who transitioned into triathlon, Karel understands the demands of both sports and excels at helping athletes improve bike execution through smarter decisions regarding gearing, cadence, power management, bike fit, and pacing strategies.

Since becoming a triathlete in 2012, Karel has completed 18 Ironman triathlons, 3 XTRI events, 2 x Breck Epic MTB stage races, Cape Epic, Pisgah Stage Race, Xterra events and several other stage races. He has qualified for and competed at the Ironman World Championship in Kona four times.

Our Coaching Team

Marni and Karel lead the coaching program and share primary coaching responsibilities across the Trimarni team. Supporting them is Assistant Coach Joe, who plays an integral role in our advanced coaching program. Joe specializes in workout analysis, training modifications, athlete support, and performance data review. His attention to detail, analytical mindset, and commitment to athlete development make him a valuable resource for our athletes.

Our Coaching Approach

We are passionate about the athlete development process and committed to providing a high level of personalized support, communication and education. Our coaching extends far beyond simply prescribing workouts. Every training plan is thoughtfully designed with attention to:

  • Endurance performance development

  • Strength training integration

  • Daily and race-specific nutrition

  • Pacing and power execution

  • Structured interval training

  • Mental performance and resilience

  • Recovery and injury prevention

  • Long-term athletic progression

Our mission is to help athletes become stronger, healthier, more resilient, and more confident. We want every athlete to arrive at the start line knowing they are fully prepared and capable of performing at their best.

Thank you for considering Trimarni Coaching. We would be honored to be part of your journey and help you achieve both your short-term goals and long-term athletic ambitions.

MISSION

We provide personalized coaching for athletes of all abilities, with a specialized focus on endurance sports. Our approach is designed to help athletes build fitness, develop skills, and achieve their performance goals while prioritizing long-term physical health, mental well-being, and enjoyment of the journey. We believe athletic excellence is best achieved through a balanced, sustainable approach to training and performance.

VISION

We strive to create a positive, supportive, and inclusive environment where athletes of all abilities can thrive. Whether your passion is triathlon, XTERRA, mountain biking, gravel cycling, or extreme triathlon, our goal is to keep the journey enjoyable, rewarding, and sustainable. Through personalized guidance and expert coaching, we help athletes build fitness, pursue meaningful goals, develop confidence, and discover their full potential both in sport and in life.

CORE VALUES

  • Protecting mental and physical health

  • Trust and loyalty

  • Communication

  • Long term development

  • Education

  • Teamwork

  • Patience

  • Integrity

  • Discipline and commitment

Individual Coaching

Our Individual Coaching Program is designed for athletes seeking a highly personalized coaching experience with ongoing support, education, accountability, and expert guidance. Every training plan is customized to your goals, experience level, race schedule, lifestyle, and performance objectives.

What to Expect as a Trimarni Coached Athlete

Customized Workouts

  • Training delivered every 1–2 weeks

  • Periodized training built around your annual race schedule submitted each December

  • Unlimited training modifications based on changes in fitness, racing, work, weather, family, travel, or life circumstances

  • Individualized training adjustments made as needed throughout the season

Recommend Training Tools

  • GPS watch with advanced heart rate features

  • Heart rate monitor

  • Bike power meter (strongly encouraged for optimal bike training and race execution)

Coach Support

  • Workout feedback and communication -unlimited

  • Communication through Training Peaks, email, phone, FaceTime, or Zoom

We believe great coaching extends far beyond writing workouts.

Testing

Performance Testing

  • Fitness testing conducted when appropriate

  • Training zones established and updated as fitness progresses

  • Detailed feedback provided following testing sessions

Strength, Recovery & Injury Prevention

A strong athlete is a durable athlete.

  • Strength training integrated into your annual plan

  • Access to the ECFIT strength training app at a discounted rate

  • Programming developed by renowned endurance strength coach Erin Carson

  • Ongoing focus on recovery, mobility, and long-term athletic development

Sport Nutrition Support

Nutrition is a critical component of endurance performance. Throughout the season, athletes receive education and guidance on:

  • Daily nutrition habits

  • Performance nutrition

  • Training and race-day fueling

  • Hydration strategies

  • Race execution nutrition plans

  • Nutrition-related questions and feedback as needed

Fully personalized daily and sport nutrition consultations are available separately with Marni and are not included in the monthly coaching fee.

Race Planning & Execution

Our goal is to ensure every athlete arrives at the start line confident, prepared, and ready to perform.

Athletes receive:

  • Race-specific advice and guidance

  • Course-specific strategies and tactics

  • Education on pacing, fueling, and race execution

  • Pre-race and post-race coaching calls, as needed

  • Post-race data review and performance feedback

  • Race result recognition in the weekly team newsletter

Additional Athlete Benefits

Exclusive Discounts

  • Discounted RETÜL bike fitting services

  • Discounts on Trimarni camps and events

  • Partner and affiliate discounts available throughout the year

Team & Community

  • Access to a supportive and knowledgeable athlete community

  • Ongoing education, motivation, and accountability from coaches and teammates

Coach Support

Education

  • Weekly team newsletter

  • Team updates and athlete highlights

  • Educational Google Drive

  • Monthly Zoom chats

  • Access to the private Trimarni Coaching Facebook community

Coaching iNvestment

Your Questions, Answered

Get in Touch

If you are interested in a training plan or individual coaching, we would love to hear from you.