Running Free with Marija Kostić — Arduua’s New Trail Running Coach
At Arduua, we believe coaching is more than just numbers and metrics—it’s about connection, confidence, and creating a deeper relationship with the trail.
That’s why we’re thrilled to welcome Marija Kostić to our coaching team, a passionate mountain runner and down-to-earth motivator who brings both technical knowledge and heart to everything she does.
Who is Marija?
Marija Kostić is a smiling soul from Smederevo, Serbia—a mover by nature, who grew up dancing, skating, playing volleyball, and soaking up every chance to be outside. Her running journey began in 2014 with a spontaneous challenge: a half marathon in Ljubljana. Two months of training and one proud finish later, she was hooked.
“I still remember how proud I was when I first managed to run 500 meters without stopping – it felt like a miracle!”
But the true turning point came in 2016, when a friend invited her to a wild weekend of vertical kilometer racing across Montenegro and Bosnia. The first start line was in Kotor, staring up at the Adriatic cliffs. That moment changed everything.
“I fell completely in love with the mountains—with their raw beauty, the challenge, the peace, and the power they hold.”
Since then, trail and skyrunning have become not just a passion but part of who she is. Whether exploring the Balkans or the Alps, racing or just enjoying, Marija feels most at home on the mountain.
The Path to Coaching
Marija didn’t just want to run—she wanted to understand how running works. She explored biomechanics, strength, and performance first through self-experimentation, then helping friends, and eventually through formal education.
She is now:
- An EREPS Level 4 Certified Personal Trainer
- Certified in Running Mechanics & Gait Analysis (Human Kinetics)
- A graduate of Experto en Descensos (TTrail Academy) with a focus on downhill running
- Experienced in TrainingPeaks coaching methods and performance data
“I coach the whole person—not just the runner on paper. Every athlete is a unique puzzle of physical potential, personal life, motivation, fears, and dreams.”
Marija’s coaching combines structured science-based programming with intuition, athlete communication, and movement analysis. She looks at stride, posture, joint control, and emotional state when building personalized training.
Coaching Style & Philosophy
What makes Marija’s coaching stand out is her ability to blend science and empathy:
- Movement analysis: Helping athletes move better and stay injury-free
- Strength and mobility integration: Especially for downhill control and joint stability
- Mental support: Building confidence and resilience on technical terrain
- Flexible, real-life plans: Designed around each athlete’s schedule and energy
- Joy-first approach: Mixing fun, challenges, and playfulness into training
“One way I keep motivation high is by adding playful elements to training – like surprise workouts, challenges, or ‘games’ that shake things up.”
Whether you’re a beginner tackling your first trail or an experienced runner seeking more confidence on descents, Marija brings curiosity, patience, and precision to your journey.
Real Coaching, Real Progress
Marija’s proudest coaching moments aren’t just about medals—they’re about breakthroughs. One of her favorite stories is helping a friend who had never run before overcome self-doubt and run her first 5K in under 30 minutes.
“She thought she simply couldn’t do it. We started slowly, and one day, she not only ran 5K—she realized she loved running.”
Moments like this, Marija says, are what keep her going as a coach.
Her Life on the Trails
Marija trains 6–7 times a week, depending on the season and race goals. Her training includes:
- Two speed-focused sessions (intervals or uphill tempo)
- Long mountain runs on weekends for volume and technical terrain practice
- Two strength training sessions: either mobility-based or power-focused
- Periodized plans that adapt week-to-week depending on race phase
She is currently preparing for the Matterhorn Ultraks Extreme, emphasizing explosive strength and downhill readiness.
“It’s not just about physical preparation – it’s also about staying mentally connected to the joy of running in the mountains.”
Joining Arduua
Marija followed Arduua for years before officially joining the team. She was drawn to the brand’s unique blend of structure, science, and genuine care.
“I wanted to be part of a team that doesn’t just coach runners – but helps them fall in love with the mountains, believe in themselves, and realize what they’re capable of.”
At Arduua, she hopes to:
- Empower trail runners of all levels, especially women and beginners
- Share knowledge on movement, strength, and downhill technique
- Support SkyCamps and in-person coaching events
- Create accessible, motivating coaching for those who feel unsure or overwhelmed
Coaching Focus
Marija especially enjoys working with:
- Runners lacking confidence on technical terrain or downhills
- Beginners transitioning from road to trail
- Women seeking empowerment in the mountains
- Athletes balancing training with work, family, and life stress
She addresses common challenges like downhill technique, underdeveloped strength, poor mobility, and mindset hurdles. Her toolbox includes video feedback, strength blocks, gait analysis, and mindset strategies to help runners overcome both physical and mental barriers.
“My goal is to coach well-rounded mountain runners, not just fast runners.”
Ready to Train with Arduua & Marija?
If you’re looking for a coach who sees you, who understands the mountains, and who combines expertise with genuine encouragement—Marija might be your perfect match.
Connect with Marija:
- 💌 Email: marija.kostic@arduua.com
- 📱 Instagram: @majche_skyrunner
Welcome to the team, Marija!
/Katinka Nyberg, Arduua Founder
📲 Sign up for Arduua Trail Running Coaching here: https://arduua.com/trail-running-coach-online/