Talking Ultra with Nguyen Si Hieu
With eight years of trail running experience, Nguyen Si Hieu has become one of Vietnam’s brightest ultra talents. Here we talk to him about his third place at Vietnam Ultra Marathon 75km and the Rinjani 100 – two results that followed his victory at the VTM70km at the start of the year.
Reflections on VUM 2025
How did you feel after finishing Vietnam Ultra Marathon 2025 with a time of 7:24:59 in third place, at that moment?
VUM 2025 is one of the most unforgettable races in my eight years of trail running. In a highly competitive race, I had to push myself from the very start and only managed to secure third place in the final few kilometers. It wasn’t until the last few meters that I was confident about my position and that brought immense joy.
Hieu at first edition of VUM
What do you think made this your most successful race? Was it your preparation, race strategy, or mental resilience that played the biggest role?
This year’s 75km VUM attracted many strong international runners, including four men with an ITRA index over 800 and three women over 730. My index is 721. I had previously finished far behind some of these runners.
For example, at VUM 2024, I finished second, but 50 minutes behind the champion, John Ray Onifa. This year, he won again, but I was only 9 minutes behind him.
More importantly, I was able to maintain a strong pace from start to finish, which shows notable improvement in my physical condition. I credit this to two changes I made at the end of 2024: doing longer road runs (previously I had rarely done road runs over 25km because I found them boring) and spending more time on warm-ups, strength training, stretching, and massage.
How is VUM 2025 different from previous races you've done? What made this one special for you?
I really love the scenery in Mai Chau Valley. Even though tourism is booming there, Mai Chau still preserves its local identity, which is amazing. Also, the high level of competition this year fueled my competitive spirit even more.
Photo of the Start and Finish area of VUM 2025
Just over a month before VUM, you won the Vietnam Trail Marathon 70km. How were you able to maintain your form? What was your recovery and preparation process like between the two events?
My training and racing seasons are scheduled for cooler months in Northern Vietnam (from September to April), and both VTM and VUM fall within this period. With eight years of running experience, recovering after VTM wasn’t too difficult. I took a lighter training load and got more sleep for about a week before returning to normal training in preparation for VUM.
Race Strategy & Experience
Hieu on his way to 3rd at VUM 2025
Can you walk us through your race strategy from start to finish? When to push the pace, and when to hold back?
My strategy was to stick with the lead pack, push harder on less technical sections, and spend as little time as possible at aid stations. My longest stop at an aid station was only 43 seconds. Even though I didn’t have a personal support crew, the event volunteers were incredibly helpful at every station.
In the final stretch, you picked up the pace to secure third place. How did you mentally and physically prepare yourself to maintain such a fast pace until the finish line?
I think it was a lucky day for me – Lodewijk wasn’t at his best at that point, while I felt strong. I took full advantage of that.
You mentioned competing against Lodewijk Vriens. How did this competition impact your racing strategy and mentality? Do you think you would have performed so well without this rivalry?
Not just Lodewijk – the entire leading group pushed me to keep going. That included Ha Hau (the women’s 75km VUM 2025 champion), Chinh, Kristian, and Alexandre. Without their encouragement, I probably wouldn’t have clocked such a good finishing time.
Looking back at the entire race, is there anything you feel you could have done better? If you had the chance to run it again, what would you change about your approach?
Honestly, I think it would be hard to do any better. Everything came together really well in this race.
Rinjani 100
Nguyen Si Hieu at Rinjani 2025
Nguyen Si Hieu with Sange Sherpa, champion of the 100 miles Rinjani 2025
Turning now to the Rinjani 100, firstly, congratulations on taking third place! What were the biggest challenges you faced during the 162km race, and how did you overcome them – both physically and mentally? This was a significantly longer distance than your recent races – how did you adjust your strategy, nutrition, and mindset to cope with such challenging terrain and elevation?
The biggest challenge for me was the steep mountain climbs – some sections had iron ladders, while others had none, and I had to cling to the grass tufts to climb. Honestly, I’m quite afraid of heights, so I felt quite nervous on those vertical sections (although I was fine on the descents). At those points, I just focused on gripping tightly and climbing carefully.
Because the race was so long, I mainly ate normal food like rice, bread, and fruit. During the day, when it was hot, I drank Tailwind to replenish electrolytes and energy. Towards the end and during the second night, I added coffee gels and had some coffee to help me get through the final two summits.
Instead of considering this as a race, I saw it as an opportunity to discover a natural wonder. So I didn’t think too much; I simply focused on myself and kept moving forward.
Rinjani 100 is known as one of the toughest mountain ultras in Southeast Asia. How did your experience at Rinjani differ from VUM 2025, both in terms of challenge and personal growth? Do you feel that your preparation for VUM helped build a solid foundation for your performance in Lombok?
In shorter races, I usually push myself to the limit on every kilometer. Even at checkpoints, I stop for less than a minute. But in long races like Rinjani or VMM 100 miles, the pace is much more relaxed, and it’s necessary to rest longer at checkpoints to refuel properly.
I set my sights on the Rinjani 162km back in late November 2024. VTM and VUM were both highly competitive races, so they were great opportunities to build the best possible physical foundation for Rinjani. After that, I moved into the final preparation phase, focusing on specific training to simulate the pace, elevation, and nutrition strategy required for such a long race.
Completing 162km and placing third is a truly impressive achievement. What does this result mean to you personally, and how has it influenced your goals for the rest of the season – particularly VMM 100km? Based on what you learned from this race, do you plan to make any adjustments to your training or recovery routine?
I won’t change much in my approach following Rinjani.
I didn’t set any ranking goals for the race, but I was hoping to finish in under 48 hours – and I’m very happy I achieved that. But more than anything, getting to experience the entire course was the most meaningful and rewarding part for me.
I’ve generally planned out my entire 2025 season, and VMM 100km is a key component of that. For me, trail running is a combination of exploring nature, pushing personal limits, and competing. VMM is always highly competitive, and this year it’s even more special as it’s part of the World Trail Majors.
Watch this space for another Q and A with Hieu, covering his mindset, training, recovery and more….
