Before getting into my interesting technique to better isolate the diaphragm, let's review an interesting paper that did attempt to better target the diaphragm with RMT. This study aimed to look at EMG of the various muscles along with pressure dynamics in subjects choosing either standard RMT or a "diaphragm targeted" technique. The RMT device was a Powerbreathe K3 (I have the K4 which will be shown in my data below).
The breathing technique was described as follows:
I have tried this myself and it is not easy! It is harder than it looks and ideally you really need three hands - one to hold the Powerbreathe, one for the abdomen and another for the chest motion. In reality the compromise is to remember how to breathe with the diaphragm and just use your hand for the RMT device.
The EMG data does show a difference in diaphragm vs accessory/chest muscle usage
The positions of
the electrodes were as follows: EMGscm was placed at the
midpoint along the long axis of the sternocleidomastoid
muscle between the mastoid process and the medial clavicle,
EMGsca was placed within the posterior triangle of the neck
at the level of the cricoid process, EMG7ic was placed in the
space of the seventh rib along the anterior axillary line, and
EMGpic was placed in the space of the second rib roughly
3 cm lateral to the sternum.
The pressure differences also supported the abdominal breathing causing better diaphragm usage:
The catheter used for EMGdi
includes two balloons for measuring esophageal (Peso) and
gastric pressures (Pga) simultaneously. Each balloon was connected
to a differential pressure transducer (model DP15-34;
Validyne Engineering, Northridge, CA). Transdiaphragmatic
pressure (Pdi) was calculated as the difference between Pga
and Peso. Absolute pressure swings were calculated as the
difference between the maximum and the minimum pressures
during each inspiration. Pressure–time products (PTP) of Pm
(PTPm), Peso (PTPeso), Pga (PTPga), and Pdi (PTPdi) were
obtained by calculating the area subtended by each pressure
trace as a function of inspiratory time.
The rate of force development (pressure time product PTP) was also in a similar direction:
And finally, a single users data:
I highlighted the diaphragm pressure in yellow. The IMTdi (right side) shows more EMG activity, diaphragmatic pressure than the standard IMT.
The discussion has several important points including:
Our findings suggest that a typical session of IMT requires
a high level of activation in the scalenes and sternocleidomastoid
to assist the diaphragm. In fact, EMGsca and
EMGscm were virtually the same as EMGdi when expressed
as a percentage of maximal activation (Fig. 1) with lower
relative EMG activity in the seventh intercostal space and
parasternal intercostals. These observations raise the question
of whether or not IMT could be improved to more effectively
target the diaphragm. There are several lines of
evidence suggesting that the diaphragm should be the most
important muscle to target during IMT.
For example, diaphragm fatigue
can cause a redistribution of blood flow from the locomotor
to the respiratory muscles (33), known as the
respiratory ‘‘steal’’ phenomenon. This sympathetically mediated
metaboreflex response reduces oxygen delivery to the
working locomotor muscles leading to increased locomotor
muscle fatigue, increased effort perception, and ultimately
reductions in exercise performance (28).
In summary, this study demonstrates that inspiratory muscle
recruitment during IMT can be altered significantly based
on the instructions given to participants. A typical bout of
IMT relies on the extradiaphragmatic inspiratory muscles to
assist the diaphragm. This may not be the optimal form of IMT
given the established importance of the diaphragm during
exercise. Simple instructions to encourage active recruitment of
the diaphragm during IMT can substantially increase the pressure
production and electrical activity of the diaphragm. Future
studies are required to determine whether IMTdi confers greater
benefits than IMT on exercise performance, diaphragmatic fatigue,
and physiological and perceptual responses to exercise.
Focused training with biofeedback:
The following RMT sessions were done using the Powerbreathe K4 with a reduced pressure setting from what I usually work with. It became clear that I have a long way to go to train myself to target the diaphragm since the standard resistance was way too high for me. As in strength training, it seemed reasonable to get my "form" proper with light weights before embarking on more challenging loads.
Using the Hexoskin shirt for diaphragmatic breathing feedback:
Now that we've established that it is possible to target the diaphragm by altering the way we breath, can we do a better job in teaching ourselves how to do this? In addition, since we don't have 3 hands, is there a way to observe the motion of the chest and abdomen as we do the RMT device? The answer is yes to both and it involves the Hexoskin shirt (see bottom of post for further links).
Since the shirt is able to calculate the total ventilation rate, it needs plethysmographic sensors in both chest and abdominal areas corresponding to where the hands would go in the above reviewed paper. So by looking at the chest vs abdominal excursions in the smartphone app, we can view our breathing pattern in real time.
How to set this up:
Make sure the screen time out is adjusted - up to 10 minutes or so.
Open the Hexoskin app.
Start your RMT app/device.
This is the main screen of the android app (iPhone should be the same)
Once you have the shirt on, the module connected, press the show sensors button (in red).
After doing this, a screen with tabs showing either "Heart" or "Breathing" will appear. Choose "Breathing"
I have circled in yellow a normal breath (both inspiration - line going up, expiration - line going down). The Thoracic/chest tracing is on the top, the Abdominal is on the bottom.
This is a normal deep breath and the thoracic/chest has greater motion than the abdominal.
Here is the transition of RMT training from "standard" to "diaphragmatic". The top line flattens since I'm not using the chest (much), but the lower line representing abdominal.
The idea to is to minimize the thoracic motion and maximize the abdominal motion. Just as in the article's instructions, you need to breath in making your belly protrude. Kind of the opposite as sucking in your chest to show off at the gym. We do not want much chest motion. Before using the RMT resistance device just try breathing this way for awhile and get used to it. Once it becomes more familiar, then try some very light resistance RMT. But realize, it may take weeks (or months) to truly succeed with this technique.
This pattern continues through the training session:
The end of training, with a final deep normal breath for comparison:
Confirmation with the Hexoskin web view:
The Hexoskin website has a much more detailed view and analysis of measurements.
Here is a segment form the Hexoskin web app showing the end of a session of RMT using the abdominal breathing technique (guided by the smartphone app live view):
The abdominal motion is in light blue, chest/thoracic in dark blue. The red circle is a typical breath in the midst of diaphragm training with excellent abdominal excursion, little thoracic motion. On the right side are two normal breaths, both lines moving in a similar fashion. This is good confirmation, but not too valuable as a biofeedback aide.
Here is a video of a shortened RMT session, starting with normal breathing, abdominal focused training and then normal again. It is a screen recording of my android phone running the Hexoskin app in "sensor display" mode.
- The diaphragm is the primary muscle responsible for respiration.
- There is a breathing technique that can target diaphragmatic function according to EMG and pressure dynamics.
- It is also possible to use the Hexoskin shirt, with it's smartphone app as a real time biofeedback device for optimal abdominal excursion as well as minimizing thoracic/neck muscle usage.
- So far, no long term study has evaluated if this technique will lead to superior RMT results.
Other related post about the Hexoskin: