Skip to content Overcoming stuttering and breaking through speech anxiety begins with understanding and mastering your primary respiratory muscle: the diaphragm. But from a physiological standpoint, does the specific costal breathing technique actually function differently than normal breathing? To obtain a clear and undeniable answer, the movements and structural changes of the diaphragm were meticulously investigated using advanced medical technology.
Below you will find the physiological results of the scientific study in which the physical effects of the Del Ferro Method were mapped live via fluoroscopy.
As part of the experiments on diaphragmatic breathing, the movements of the diaphragm were observed under X-ray fluoroscopy. During these trials, the excursions and structural changes of the diaphragm were examined using fluoroscopic imaging. Before describing these experiments, several key concepts must be clarified.
The diaphragm is a flat muscle that forms the partition between the thoracic and abdominal cavities. Within the body, this muscle is dome-shaped, with the apex of the dome slightly flattened at the top. This flat central portion of the muscle is called the central tendon (centrum tendineum), which consists of an aponeurosis. The space formed between the border of the diaphragmatic muscle fibers and the thoracic wall is referred to as the costodiaphragmatic recess. Do you want to dive deeper into the medical anatomy and embryonic development of this musculotendinous sheet? Be sure to read our background article on the anatomical function of the diaphragm.
The trials consisted of measuring the excursions of the diaphragm in a number of subjects during maximal inhalation and exhalation using their habitual breathing technique. Subsequently, the same measurements were performed while the subjects were instructed to breathe according to the Del Ferro diaphragmatic method. These measurements were repeated several times, including in reverse order. The average result (measured value) per individual was taken as the representative standard.
A subsequent experiment consisted of measuring diaphragmatic excursions for both types of breathing, during which the subjects sustained three notes—singing tones—for as long as possible, followed by a consecutive trial where a hissing sound (sibilant) was sustained for as long as possible. The results of these trials are presented in Figure 1.
Figure 1
Below are the translations of the Dutch texts from the image:
SIS-KLANK → HISSING SOUND
NOTEN-KLANK → SINGING TONE
MAXIMALE EXPIRATIE → MAXIMAL EXPIRATION
RESP. INSPIRATIE → RESP. INSPIRATION
CENTRUM TENDINEUM → CENTRAL TENDON
DIAFRAGMA EXCURSIES IN CM. → DIAPHRAGMATIC EXCURSIONS IN CM.
SINUS COSTALIS → COSTAL SINUS
normaal → normal
delferro → Del Ferro Institute
T = getraind → T = trained
N = normaal → N = normal
S = stotteraar → S = stutterer
Since the central tendon (centrum tendineum) exhibited limited mobility in several subjects, we determined the excursions of the central tendon as well as those of the costodiaphragmatic recess (sinus costo-diaphragmatica) in a large portion of these individuals. Figure 1 demonstrates that the excursions of the diaphragm and those of the costodiaphragmatic recess vary significantly across the various subjects.
Furthermore, it is evident that most subjects demonstrate a significantly lower diaphragmatic position during maximal inhalation using the costal breathing method compared to the position achieved after maximal inspiration using their habitual breathing technique.
On average, the excursion of the central tendon in the caudal direction (downward) shows an increase of approximately 25%, while the displacement of the lower border of the costodiaphragmatic recess is as much as 35% greater during maximal inspiration using the diaphragmatic technique compared to habitual breathing.
Door ons is er bij maximale uitademing geen duidelijk hogere stand van het diafragma gevonden bij het toepassen van de twee verschillende ademhalingstypen. Bij een herhaling van deze proef, terwijl de proefpersonen zo lang mogelijk drie noten zangtoon aanhielden, bleek er echter wél een verschil te constateren ten gunste van de middenrifademhaling.
In the three-vocal-tone trial, the central tendon was found to rise approximately 29% further, and the increase in the displacement of the costodiaphragmatic recess was as much as 42%. The same trials repeated with a sibilant sound yielded values of 20% and 25%, respectively.
We wondered what significance a lower position of the diaphragm might have for the volume of the thorax. For me as a radiologist, evaluating the thoracic volume is the primary consideration. Figure 2 displays the chest radiographs of a subject breathing in the conventional manner. The top-left radiograph was taken during maximal expiration, the top-right during normal expiration, the bottom-left during normal inspiration, and subsequently the bottom-right during maximal inspiration.
Figure 2
From all these radiographs, taken in anteroposterior and lateral directions, we have superimposed the contours, as displayed in Figures 3 and 4. These figures demonstrate that when the thoracic volume increases from maximal expiration to maximal inspiration, we are dealing with an expansion of the volume in all dimensions.
Figure 3
1 | Maximal expiration
2 | Normal expiration
3 | Normal inspiration
4 | Maximal inspiration
Figure 4
1 | Maximal expiration
2 | Normal expiration
3 | Normal inspiration
4 | Maximal inspiration
Subsequently, we superimposed the contours (Figure 5) of radiographs taken of a subject who, during one exposure, inspired maximally in the conventional manner, and during the other exposure, inspired maximally using the Del Ferro diaphragmatic breathing technique. It could be argued that a shift in thoracic volume occurs in favor of the basal—lower—lung segments, which would consequently result in an altered ventilation distribution. Given that the basal region of the lungs is better perfused, this could lead to an improved ventilation-perfusion ratio through the application of the Del Ferro diaphragmatic breathing technique.
Figure 5
N | Normal
F | Diaphragmatic breathing
Using X-ray fluoroscopy during the experiments, it was indisputably visualized to what extent a conscious use of the diaphragm results in a more pronounced flattening of the diaphragmatic dome.
In absolute terms, this presents a spectacular contrast: during normal breathing, the central tendon descended an average of only about 1.5 cm. In contrast, with the specific Del Ferro diaphragmatic breathing, this displacement sometimes reached as much as 6 cm. This directly accounts for the massive increase in functional lung volume and physical control over the airflow.
Although the above measurements demonstrate the physical displacement of the diaphragm in centimeters, the visual observations of the fifteen subjects at the Mariastichting are at least as fascinating. Under X-ray fluoroscopy, it was precisely documented at the time how a speech blockage physiologically disrupts the natural airflow.
When struggling with a speech blockage, the X-ray images reveal that the upward respiratory movement of the diaphragm is abruptly disrupted in the following ways:
Mild hesitations (fluttering)
During a brief interruption in speech, the diaphragm suddenly begins to vibrate or ‘flutter’ slightly. Exhalation stagnates, often followed by a reflex-like, brief inhalation before exhalation and speech are laboriously resumed.
Severe blockages (physiological hesitation)
With more severe stuttering, a more intense form of fluttering is visible. From a physiological standpoint, the diaphragm appears to ‘hesitate’ between inhalation and exhalation. It takes the body audible and visible time to release this blockage.
Continuous stuttering (the cogwheel movement)
During a continuous speech blockage, a constant, trembling vibration of the diaphragm can be observed throughout the entire exhalation. Sometimes the muscle jerks upward in a sort of ‘cogwheel movement’.
All the well-known external spasms, such as pressing the lips together or the accompanying movement of the head, are simply the result of this internal physiological muscle struggle. At the moment of stuttering, you attempt to speak while the diaphragm is actually flattening (inhaling). Because this is anatomically impossible, the airflow locks up.
These radiological results provide the hard, physiological proof that the Del Ferro costal breathing method differs fundamentally from habitual breathing. Through targeted training of the diaphragm, you not only optimize lung ventilation and perfusion, but you also regain the complete physical control necessary to speak stutter-free.
This scientifically demonstrates that you can actively influence and correct the physical cause of stuttering. This Dutch study therefore aligns seamlessly with other worldwide medical breakthroughs. Read more here about the international scientific research by prof. P.T. Macklem.
Would you like to experience firsthand how we apply these physiological insights in practice, or would you prefer to continue exploring? Choose your next step below:
How the Method Works
Discover how we translate this physiological evidence into a practical speech technique. Explore our 5-step plan here.
Read More >
Scientific Validation
Read the comprehensive overview of all medical and scientific research regarding stuttering.
Read More >
Aftercare & Securing Results
Medical evidence is one thing, but how do we sustain it? Learn how our aftercare program prevents a stuttering relapse.
Read More >
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.
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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.
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