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In traditional speech therapy and stuttering therapy, the prevailing consensus is often that stuttering is a stubborn condition you simply have to live with. For nearly 50 years, the Del Ferro Institute has been proving the exact opposite.
When you are looking for a method to permanently overcome stuttering, a reliable scientific foundation for stuttering therapy is essential. The core of our method is physical: stuttering is caused by uncontrolled movements of the diaphragm muscle.
The diaphragm is responsible for as much as 90 percent of breathing. The Del Ferro speaking technique consciously controls the diaphragm, making stuttering impossible. An essential part of the course is automating this process—meaning fluent speech becomes a natural, effortless part of your everyday life, until no one would ever guess you used to stutter.
Curious about how this unique method originated? Read the extraordinary story of its discovery below.
The Del Ferro Method was discovered by chance in 1978 by the American heldentenor and vocal coach Len Del Ferro. One of his students was a German tenor who took singing lessons with him to perfect his vocal technique. However, in everyday life, this man turned out to stutter severely.
This created a fascinating paradox: as is the case with almost everyone who stutters, this tenor could sing beautifully and fluently during his singing lessons without any hesitation. But as soon as he tried to speak again after the lesson, his speech blocked completely.
As an opera singer, Len knew better than anyone that conscious control of the diaphragm muscle is the foundation for a powerful singing voice. When he taught the German singer the diaphragm technique, something remarkable happened.
The tenor discovered a remarkable side effect. By applying the newly learned diaphragm control, he was suddenly able to speak completely fluently for the first time in his life. His stuttering had completely disappeared.
Len Del Ferro realized that he had accidentally uncovered the key to solving a global problem. To medically prove his discovery, he formulated a scientific hypothesis that he had extensively tested by medical professionals.
After conclusive scientific proof was provided, he shaped his unique insights into a reproducible methodology: the Del Ferro method.
This success had a profound impact on the rest of his career. He left the opera world behind and focused entirely on his new mission: it was time to give as many people as possible a stutter-free life.
Len Del Ferro’s discovery did not go unnoticed in the medical world. His hypothesis—that stuttering has a clear physiological cause linked to the functioning of the diaphragm—became the subject of scientific research.
In 1978, Dutch neurologist Dr. J.C.J. van Hemert was the first in the Netherlands to scientifically investigate Len Del Ferro’s discovery. This study took place at the Maria Stichting hospital in Haarlem.
Using X-ray fluoroscopy, he was able to observe precisely what happens inside the body during stuttering. This revealed that the diaphragm makes uncontrolled movements while speaking.
Neurologist Dr. Van Hemert authored a comprehensive chapter on the diaphragm for one of Len Del Ferro’s books. Read an abridged version here about how the diaphragm works and how it can be trained.
Dr. J.C.J. van Hemert’s research provided the initial scientific evidence of the diaphragm’s role in stuttering. Follow-up research by radiologist Dr. H.A.S. Lemmers further investigated this phenomenon, validating it through concrete measurements.
At St. Elisabeth Hospital in Tilburg, Dr. Lemmers conducted this research alongside pulmonologist Dr. Verpalen and Dr. De Groot. Using X-ray fluoroscopy, among other techniques, they examined the movement of the central tendon of the diaphragm.
The measurements demonstrated that when applying the Del Ferro speaking technique, this central tendon lowers by up to 6 centimeters, compared to just 1.5 centimeters during regular breathing.
This means that the Del Ferro technique has a direct and powerful influence on diaphragmatic function, further substantiating the role of the diaphragm muscle in stuttering.
Following the scientific evidence gathered in the Netherlands, Len Del Ferro wanted to have his discovery investigated internationally. He contacted Prof. P.T. Macklem of McGill University in Montreal, Canada, one of the most renowned respiratory physiologists of his time. He presented Macklem with his hypothesis regarding the role of the diaphragm muscle in stuttering, after which Macklem was convinced to research it further.
Together with an international research team, Macklem spent three years investigating what happens inside the body during stuttering. Their research revealed that uncontrolled movements of the diaphragm muscle disrupt airflow and air pressure against the vocal cords. As a result, the natural coordination between breathing and speech is broken, making fluent speech impossible.
The findings were published in 1990 in the medical journal American Review of Respiratory Disease under the title Respiratory Muscle Incoordination in Stuttering Speech. After many years of dedication, Len Del Ferro had secured vital international scientific support for his hypothesis.
To objectively track the results and progress of every participant, we carefully measure severity of stuttering and overall quality of life at various stages before and after completing the Del Ferro Method. This provides every student with clear insights into their personal growth and confidence in maintaining long-term stutter-free speech.
Within regular speech therapy, traditional stuttering centers, and other stuttering therapies (which are often based on the theories of Charles van Riper and Wendell Johnson), it is often taught that stuttering can no longer be cured after the age of six.
There, participants are encouraged to accept their stuttering, learn to stutter fluently, or even let their environment stutter along with them. Slogans like ‘once a stutterer, always a stutterer’ are unfortunately the norm there.
For almost fifty years, the Del Ferro Institute has been proving that stuttering can be completely cured. We do not view stuttering as an incurable psychological defect, but as a physical faltering that you completely and permanently overcome through targeted muscle training. Our stuttering therapy is there for everyone who longs for a 100% stutter-free life.
Are you curious about the exact physical and mental technique behind this long-standing success?
At the age of twenty, I decided: this has to stop. It was holding me back in everything - in my sports, my studies, my future. I wanted to reach my full potential, and that was only possible if I could speak freely. The Del Ferro Method made that happen. Finally, I could speak my mind without fear. I wish that feeling for everyone who stutters.
~ Del Ferro Ambassador Jeff Tesselaar
Permanently overcome stuttering and speaking anxiety by training your most important breathing muscle: the diaphragm. The Del Ferro Method restores your control so you can speak fluently and confidently in any situation—from an informal chat to presenting before a full room. Select the training below that matches your age group and learn to speak stutter-free.
6 to 12 Years
13 to 17 Years
Ages 18 and Up
You will notice the results of the training immediately. Because the technique directly targets the diaphragmatic muscle, you learn how to completely eliminate the physical blockage on the very first day of the course. The fantastic result? You will speak completely stutter-free and fluently from the very first day of training.
With this valuable, practical tool, you immediately regain control over your breathing and your voice. The logical consequence is that your self-confidence receives a massive boost and your speech anxiety decreases.
Yes. Whether you struggle with audible stuttering, such as repetitions and prolongations, or try to hide your stuttering by avoiding words, using synonyms, or relying on workarounds: the underlying stuttering mechanism is exactly the same.
In all cases, the diaphragm muscle plays a key role. When control over the breathing mechanism is disrupted during speech, the diaphragm muscle can produce uncontrolled movements. Our training addresses this underlying source directly by systematically training the diaphragm muscle.
This way, we focus not only on visible stuttering or the tricks used to disguise it, but on the underlying mechanism behind it.
Conventional speech therapy often operates from an acceptance model: you learn to ‘stutter fluently’ or to accept stuttering as a part of who you are.
We do not focus on symptom management or resignation, but on truly overcoming stuttering.
Because we diverge from conventional speech therapy and stuttering centers, we have created a page dedicated to applying for a reimbursement for this stuttering therapy.
No, that is not the ultimate goal. In the beginning, you use the technique as a tool. Our method is built on a clear 5-step plan,
Our intensive aftercare program is specifically focused on successfully anchoring fluent speech into your daily life.
Just like you once consciously learned to drive a car or ride a bike and now do so automatically, stutter-free speech will also become completely automatic and natural over time.
In short: there is no difference; it is exactly the same. The term ‘costal breathing’ was introduced in 1978 by Len Del Ferro, the founder of our method. Through years of continuous development, this term gradually evolved into the name we still use today: diaphragmatic breathing.
Len Del Ferro discovered how effective training this specific muscle is and wrote a total of 3 books about it:
On Stuttering: in which he explains why stuttering is permanently a thing of the past thanks to costal breathing.
On Hyperventilation: focused on overcoming hyperventilation, stress, and anxiety symptoms through proper breathing.
For Athletes: specially written to help athletes increase their endurance and recover faster.
Whether you call it costal breathing or diaphragmatic breathing: it is and remains the key to a healthy and powerful life.
Do you have any other questions? Schedule a consultation at your convenience, or message us directly via WhatsApp:
Most people who stutter receive the same advice: you have to learn to live with it. At Del Ferro, we have taken a very different approach for nearly 50 years.
What if the solution doesn’t start with accepting stuttering, but with addressing what physically happens during speech?
The Del Ferro Method offers a targeted solution for stuttering that remains overlooked in traditional speech therapy.
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At Del Ferro, we look at stuttering very differently. After all, the key to fluent speech does not lie in your head, but in a specific physical action that gives you immediate control.
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Nearly everyone who stutters is told the same thing: you just have to learn to live with it. At Del Ferro, we look at this very differently.
After all, the key to fluent speech does not lie in your head, but in a specific physical action that traditional speech therapy often overlooks.
Leave your email address and discover right away how to regain complete control over your voice.
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