Skip to content Neurologist Dr. J.C.J. van Hemert, then affiliated with the Maria Stichting in Haarlem in the Netherlands, was the first to test Len Del Ferro’s physiological hypothesis. Using X-ray imaging, this historic research on stuttering scientifically proves that the diaphragm muscle makes uncontrolled movements during a speech block.
As a result, the airflow is severely disrupted, causing exhaled air to pass through the vocal cords in fits and starts, leading to stuttered speech. This medical foundation provides black-and-white proof that stuttering has a physiological cause. Below, you can read the original, official report written by Dr. Van Hemert:
When I first spoke with Leonard del Ferro about his method and its application, a quote by the stutterer Nuttall came to mind: ‘Whoever finds the solution to the stuttering problem will also have found the solution to the rest of humanity’s problems.’ Although this statement mainly expressed the distress of an individual patient, it clearly indicated that many attempts to solve the stuttering problem did not yield the desired results. The wide range of therapies developed to treat this disability appears to be a consequence of the lack of agreement, as to what stuttering actually is.
The Del Ferro Method was not developed according to conventional theories on the causes of stuttering. This method is based on the physical reality of people who stutter. Its core premise is that physical functioning directly affects emotional life and self-esteem.
What makes the Del Ferro Method unique is its predominantly physical approach through training the diaphragm. The diaphragm is a muscle plate that forms the separation between the thoracic and abdominal cavities. In this context, I refer to observations by radiologist H.A.S. Lemmers and other research into Leonard Del Ferro’s discovery. The Del Ferro method has been scientifically examined at various universities and hospitals.
The research I led myself included studying the diaphragm, under X-ray screening, of people who stutter and do not stutter. This revealed that the diaphragm of stutterers makes irregular movements while speaking. It also became clear that a person who stutters attempts to speak and inhale simultaneously, which is impossible even for individuals who do not stutter.
Application of the Del Ferro Method shows that controlling the diaphragm can lead to overcoming stuttering. It is remarkable that many people who stutter, having previously undergone numerous therapies without actual results, achieved immediate success with this method. Almost all people treated at the Del Ferro Institute show marked improvement within just a few days.
Conclusion: the Del Ferro Method offers tens of thousands of people who stutter in the Netherlands — not to mention hundreds of thousands in the rest of the world — a realistic prospect of a permanent solution to their problem.
In addition to his specific research on stuttering, Dr. Van Hemert mapped out the complete medical physiology, muscle fibers, and trainability of this respiratory muscle. Click here to read the full article on how the diaphragm functions.
Dr de Grood, neurosurgeon, wrote:
The undersigned declares that, for several years, together with colleague M. Verpalen, a pulmonologist in Tilburg, he has scientifically monitored the Del Ferro Method for the treatment of stuttering.
The conclusions are:
Del Ferro’s Method relies on training the diaphragm, teaching random control of the contractions of this muscle.
It has been shown that after treatment with the Del Ferro Method, the involuntary muscle contractions have disappeared.
Based on these data, which have been confirmed by other researchers, including Prof. Macklem from Montreal , we can conclude that, on medical grounds, the Del Ferro treatment is an effective method for treating individuals who stutter., zijn bevestigd, kunnen wij concluderen dat de Del Ferro behandeling op medische gronden bij het behandelen van stotteraars een goede methode is.
How the Method Works
Discover how we translate this physiological evidence into a practical speech technique. Explore our 5-step plan here.
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Scientific Validation
Read the comprehensive overview of all medical and scientific research regarding stuttering.
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Aftercare & Securing Results
Medical evidence is one thing, but how do we sustain it? Learn how our aftercare program prevents a stuttering relapse.
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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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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
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.
Sign up now and get the insights you won’t find anywhere else:
