Our trainers

Our trainers

Welcome to our trainers page!

Here, we would love to introduce you to the esteemed trainers of G.S.B.V. de Mattekloppers. They all have written a short story about their martial arts lives, and how they ended up in our association. Have fun reading, or come by and listen to their amazing stories during training! :)

Simon Leistra

Competitional Judo

My career as a judo coach began at the end of my education at the Academy for Physical Education in Groningen. The first step in my coaching career took place at judoschool Dijkmansport. After this valuable experience, I dedicated five years to coaching at Bushido Winsum. Here, I was able to further develop my skills and make a positive contribution to the development of young judokas.

My coaching career took a next step at BVHS in Hoogezand, a period during which I also provided Wednesday afternoon training sessions for judokas at Veendam Judo School.

Ultimately, I took on the role of head coach at G.S.B.V. de Mattekloppers, a position I have proudly held since 2006. Throughout my entire judo career, I have dedicated myself to not only enhancing the athletic performances of my judokas but also supporting them in finding balance between sports, academics, and their social lives. I strongly believe in the development of young adults, both within the realm of judo and beyond, and I find it fascinating to guide them on this journey.

Providing training to judo enthusiasts every Monday at the regional training sessions and on Wednesdays during competition trainings, along with guiding them during tournaments, preferably alongside my judo colleagues, brings me great satisfaction. It is this blend of training, development, and collaboration that makes my work as a judo coach so rewarding and challenging.

Best regards,



Casper Manting

Technical Judo

My name is Casper and every Thursday evening I teach technical judo training at G.S.B.V. de Mattekloppers.

I think judo is a wonderful sport because it can be very technical and at the same time use intuition and a sense for timing and movement. I like to call this the judo sense. To develop this, during trainings I do a lot of romping, balancing and coordination games. In this way, I want to make my training accessible to novice judokas and make the lessons enjoyable for everyone. In addition, judo allows you to endlessly combine techniques and throws, making it a complete sport. As a result, for advanced judokas as well, there is always something new and challenging.

I once started judo myself because of my older brother, who was already doing it. Then I quit for a few years before picking it up again at the age of sixteen. From then on, I have been practicing judo quite enthusiastically. Within judo, I first attended many technical trainings, practised katas, and participated in kata competitions. Since 2017, I have been training with the Mattekloppers and started focusing more on competitive judo. In the same year, I started at the Academy of Physical Education (ALO in Dutch) to become a teacher. At the ALO, I got the opportunity to do the judo teacher A course and I didn't hesitate even one moment to say yes. So I started giving judo lessons and since September 2023, I have been doing so with great pleasure at the Mattekloppers. The great thing about teaching at the Mattekloppers is that you have judokas of all levels on the mat. From people just starting out to experienced competitive judokas. By combining play and technique, I want to challenge everyone at their own level and pass on my enthusiasm for judo.

Hope to see you soon in the dojo!

With best regards,



Renger Boersma

Technical Jiu-jitsu

I am Renger Boersma, the ju jitsu teacher of the Mattekloppers since 2002. Before this, I was a ju jitsu teacher for the Hanzesport, but in 2002, ACLO and Hanzesport continued under one roof.

In February 1984, I started teaching the students of the social academy "Wolweze" in Leeuwarden. I have been giving training to students for 40 years, with short excursions here and there at regular budo associations. I know that students are critical pupils, but that keeps you as a teacher alert. Especially in the starting years, teaching was accompanied by a sociable "3rd half", where some alcoholic beverages were consumed as well. For me, in teaching, there are 2 central aspects: something should be learned, and there must be fun. Moreover, I enjoy seeing my pupils grow, both in their ju jitsu skills and their personal development from young adolescents to adolescents. Therefore, I really enjoy giving training to students!!!

My passion for ju jitsu flows from the fact that it is very multidimensional, something I missed in karate and judo. For me, ju jitsu is self-defense: one who is not strong must be smart (and a bit mean, if necessary). Always taking into account that you are being attacked (physically) and that defense is proportional to the attack! My credo is therefore "self-defense through self-control".

I hope to see you soon on the mat.

Kind regards,



Matthijs Elema

Technical Judo

Coming soon


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