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Vonsy's TRI Family consists of amazing athletes that are guided by our 3 coaches, Natasja, Per & Yvonne (Vonsy). Bellow you will find more information about us and you can see which coach fits best to your abilities and personal preferences. If you like more information then you can of course shoot us a email to

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Yvonne van Vlerken

Yvonne van Vlerken is the Head Coach of Vonsy's TRI Family. As a athlete she was known as Vonsy and now since 6 years as a coach she's continous to use her nickname Vonsy, this is also the reason and the base of the name of our amazing team. After being a professional triathlete under the wings of 3 amazing coaches, Frank Senders, Mario Huys and Siri Lindley, Vonsy retired in 2019 and said farewell to the Triathlon world as a athlete herself . 

Yvonne coaches and trains with the methods taught by her own coaches,but combines all of this with her background as personal trainer in several sport arts and all the latest scientific knowlegde especially concerning women in sports . 

Just going back all the way to 2000,Yvonne started competing in Triathlon and Duathlon and has been very successful in her career in both sports. She started racing professionally in 2005, after great success between 2007-2011 she then lost her joy and passion for her beloved sport and had a year where she didn’t perform on the highest level. At the point of stopping and getting back to her job as a sports instructor and sports massage therapist, Siri crossed her path and changed all of this, her nick name went from the "flying blonde Dutch girl" to just "Vonsy". Within one year she was back to her winning ways, loving the sport even more than ever and found the way back to being her shiny and happy, healthy self again. Her biggest successes would follow in the years to come, also the last couple of years where she was self coached saw PB's and big victory's before hanging up her cycling shoes.....She still run's on a pretty high level, showing women that with the age of 45 you can still improof and scoor personal bests. With a 2:39 marathon in Berlin she keeps on being a inspiration for many.

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Natasja Daniels

My interest in sports didn’t start until the age of 16. I started with squash, 

kickboxing and lifted weights with the guys. Bought a bike, started running 

and found my passion in endurance sport. The passion for cycling grew by 

the year, got myself a coach and entered the world of Granfondo’s. With 

several podium spots in single and multiday events, my interest grew not 

only in the sport, but also in the art of nutrition, strength training, gear, bikes 

and training overall.  

As I was also quite good in trailrunning with top ten spots in the Eiger trail 

and Matterhorn Ultraks, triatlon seemed the next step if it wasn’t for the 

swim part!  At the age of 42 I couldn’t swim 25m crawl.  And it was a bumpy 

road to where I’m now, so if there is anyone who knows how though this is, 

it’s me.

My passion for sports grew so big that I decided to make a career switch.  

Started studying again and am now licensed as a personal-,strength-and mobility trainer and Ironman Certified Coach.  

In my search for answers why woman respond different to training as man, 

I heard about Dr. Stacy Sims.  She is an authority in the female athlete and 

author of ”Roar, woman are not small men”. This was an eye opener for me 

and I didn’t hesitate a minute when she started to teach about the female 

athlete.  After finishing her second course “Menopause for athletes” I feel 

I have the knowledge to train woman of all ages on a different level than 


I may not be a pro athlete, but I’m an Ironman, finished multiple 70.3 events 

with podium spots, Belgian title in Duathlon,… but most of all I have a lot of life experience, know what it is to be an age-grouper and how to combine 

work with training, have had different coaches over the years (including 

Trisutto and Yvonne Van Vlerken) and learned from all off them.  

I believe my passion, my knowledge and my experience are my strongest 

assets to make you a better athlete.

As a bonus you will be part of the amazing Vonsy´s Tri Family and as we say, it’s not just swim-bike-run, it's developing yourself overall and increasing your quality of life. 

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Per van Vlerken

My triathlon career started as a young kid at the age of 7 years. 

Back in the 90s I was part of the first kids triathlon in my home town Leipzig. 

There was just one problem I couldn´t even swim. As it was all just for fun, it was no problem to skip the 1st discipline and I just started with the bike part! This was the point were the triathlon fire started to burn. As a junior I improved my swim, bike and run over the years. My first goals were the German Champion title and qualifying for the junior European Championships. After 3 years in the junior national team I missed the step to the elite national team and I realised that the olympics were to far away for me. Now I'm 38 years old and a long distance pro athlete since over 14 years. For me it was the right decision to switch to long course Triathlon, I am very happy with my whole life, training, racing , coaching and just doing what I love! The biggest goal for me now is to win a Ironman after several podium finishes and to finish under 8hrs as my PB is 8:00:30"hrs. I have been coached by Siri Lindley, Jo Spindler and Guido Vroemen and since 2020 joined my wife her Team as a coach. I decided to step up and coach my own Athletes under the wings of Vonsy´s Tri Family. As our two coaches Natasja and Vonsy are Female specialised, I'm responsible for all the men in our team. Together we combine 48 years of Triathlon experience, the knowledge we have together and gained from courses, former coaches is huge, this added to the studies we all have done, sports science, sports massage therapy, personal trainer and more, make’s the perfect combination to help any Triathlete, no matter what level, to get the best out of themselves. We all do this with love, gratitude and so much passion for our sport, that success is almost unfeasible. We have grown to amazing team here in Europe and Vonsy´s Tri Family feels more like a big family than a Triathlon Team. It’s great to be part of a world wide Triathlon team with so much amazing powerwomen in there, it’s also pretty cool to be the only Men coach of the team. Surrounded by great women isn’t bad at all :-) 

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