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Top athlete and decathlete Jeff Tesselaar (ranked 17th in the world), who rediscovered his voice and athletic freedom after years of stuttering thanks to the Del Ferro Method, has been serving as a proud ambassador since 2025 to prove that a stutter-free life is possible for everyone.
Former Dutch Member of Parliament Femke Merel van Kooten, who successfully overcame her own stutter at a young age thanks to the Del Ferro Institute, has served as a proud ambassador since 2020, dedicated to inspiring others to achieve their dreams.
As the director and driving force behind the Del Ferro Institute, Ingrid del Ferro has spent decades helping people worldwide break free from stuttering and breathing-related issues such as hyperventilation and burnout.
Since 1978, the Del Ferro Institute has been a globally recognized center of expertise for permanently overcoming stuttering and breathing-related complaints. While traditional speech therapy often views stuttering as incurable and focuses on acceptance, Del Ferro has proven for nearly half a century that stuttering can be completely overcome.
Scientifically Proven Cause and Solution
The unique strength of the Del Ferro Method lies in addressing the physical source: the diaphragm muscle. Scientific research has shown that stuttering is a direct result of irregular, jerky movements of this primary breathing muscle.
Through targeted, physical training, the participant learns to fully control this muscle, making stuttering physically impossible. This active approach is supported by a standardized, scientifically oriented measurement protocol (OASES) to objectively and uniformly record its effectiveness.
Results from Day One
With a track record of over 13,000 successful participants, the method offers an unparalleled guarantee of results:
Broader Field of Expertise
Although Del Ferro is synonymous with stuttering therapy, the technique is also successfully utilized for: (Stond al ingevuld)
| Subject | Stats & Details |
| Experience | Since 1978 (nearly half a century of experience) |
| Former Participants | Over 13,000 individuals successfully helped |
| Method | Physical diaphragm technique + mental mindset training |
| Target groups | Children, teens, adults |
| Location | Amsterdam (in-person) and worldwide online & private training |
Multi-event athlete Jeff Tesselaar won silver in 2025 at the European U23 Championships in Bergen, Norway. An impressive achievement that was made possible in part thanks to the Del Ferro Method.
For years, Jeff felt trapped in a “stuttering cage.” For someone as naturally extroverted as him, it was a daily battle. Winning on the track? He almost dreaded it, preferring to avoid post-race interviews entirely rather than expose his stutter.
Until 2023, when he underwent Del Ferro stuttering therapy. Since then, Jeff has spoken freely and with absolute confidence—both at home and on the track.
“I want everyone to experience the pure sense of freedom that I feel today.”
His message to anyone who stutters:
“Turn the grief of stuttering into sky-high motivation. With the help of the Del Ferro Method, the life of your dreams is waiting for you!”
While others thought I was fighting for medals, I was mostly battling my stutter
Jeff Tesselaar, an elite athlete who has been stutter-free for three years, shares in this video why he is now dedicated to serving as a Del Ferro ambassador.
He knows better than anyone the profound toll stuttering takes—how it restricts who you dare to be, what you say, and which situations you face or actively avoid. According to Jeff, stuttering is only a small part of a speech challenge; the rest lies deep within.
That is why he aligns himself with Del Ferro’s mission: to build a stutter-free world.
Not only by helping people speak fluently, but by inspiring them to be fully themselves once again. His message is therefore clear:
Let’s ensure that in a few years’ time, there will no longer be a need to organize World Stuttering Day.
Photography by Bjorn Paree
No. Scientific research demonstrates that stuttering has a physical cause: irregular, jerky movements of the diaphragm muscle. Although emotions can aggravate stuttering, the root cause lies in the respiratory muscle, which is responsible for 90% of our breathing.
The difference lies in the objective. Conventional speech therapy often operates on the principle that stuttering is incurable, focusing primarily on acceptance and coping mechanisms.
Del Ferro embraces the philosophy of overcoming, not accepting. We train away the physical cause, making stuttering physically impossible.
The technique is immediately effective. When the diaphragm method is applied correctly, participants speak completely fluently from the very first day of training. The foundation for lasting freedom of speech is established during an intensive program of just 4 or 5 days.
Yes. The method is based on the physical laws of breathing. To objectify the results, the institute implements the OASES approach (Overall Assessment of the Speaker’s Experience of Stuttering), a scientific measurement protocol that uniformly records its effectiveness.
We treat children (from approximately 6 years old), youth, and adults alike. With a track record of over 13,000 participants since 1978, we have experience with all forms and degrees of stuttering.
Yes. Our database contains countless examples of former participants who remain completely stutter-free, even 40 years later. However, success depends on the participant’s discipline to consistently apply the learned technique in the beginning.
