Joined: 27 Jun 2005
|Posted: Tue Aug 14, 2012 7:32 am GMT +0000 Post subject: Breathing
|I have a natural tendency to take shorter faster breaths during intense training.
Is this incorrect? Should I train myself to take longer, slower/deeper breaths?
It seems like I can control my heart rate better with slower breathing, but I have to concentrate on that more.
|The Bike Doc
Joined: 08 May 2003
Location: Corpus Christi and Warda, Texas
|Posted: Sun Aug 19, 2012 12:48 pm GMT +0000 Post subject:
There have been several interesting theories on breathing that have been offered over the years. My favorite myth is to breathe only through the nose, great idea for someone without nasal congestion, relaxed and not partaking in rigorous exercise which demands copious quantities of inhaled air that exceeds the capacity of the smaller nasal passages (relative to the mouth) to deliver. Look at all the Olympians (MAXIMAL Vmax achievers) partaking in the high intensity aerobic competitions such as swimming, running, bicycling or cross country skiing and see how many of them only breath through their nose during competition. My last watching of these fine athletes showed them all mouth agape and huffing hard, deep and fast.
Short answers to your questions are yes and yes. Here is why (the looong answer).
Deeper slower breathing, in theory, will deliver more minute volume of air to the lungs, a term called minute ventilatory volume (MVV). It is a formula calculated by respiratory rate (RR) x tidal volume (VT) = MVV.
Typical tidal volume (VT) at rest for an adult is 6mls per kilogram of lean (ideal) weight. This can go up to 12 mls or more per kilogram of ideal weight with exercise.
So a resting MVV for a 70 kg adult with a respiratory rate of 12 would be 6 x 70 x 12 = 5,040 mls or ~ 5 liters/minute.
At exercise, the respiratory rate can jump to twice or more that resting rate and with a doubling or more of the tidal volume. So for a respiratory rate of 24 and tidal volume of 12 mls/kg, the increase in the MVV would be: 12 x 70 x 24 = 20,160 mls or ~ 20 liters/minute.
Now we have to take in another factor called dead space. Dead space is the amount of air that move in and out of the airway from the nose & mouth through the pharynx, trachea and bronchial tree before it reaches the working part of the lungs called the alveoli where oxygen it absorbed into the blood and carbon dioxide is taken up from the blood. Any air that is in the space from the mouth/nose to the lungs that is not alveolar space is called dead space (VTd) and no oxygen-carbon dioxide exchange occurs. It does not do any physiologic work and is therefore dead air. It is ~2mls/kg. So the effective tidal volume or the alveolar tidal volume is reduced by 2mls/kg/breath.
So let’s take the 70kg rigorously exercising adult and look at the minute ventilatory volume again and work into the equation reduction in tidal volume with shallow breathing at a rapid rate and slower but still elevated breathing rate. Let’s use a 30% reduction in the tidal volume with a 30% increase in the respiratory rate and calculating the alveolar tidal volume (VTa) and see what happens to the minute ventilatory volume at the alveolar level (MVVa).
Rapid, shallow breathing rate of 30 the equation works out:
RR 30 x VTa (VT 12 x 0.70 – VTd 2) x 70 = 13,440 mls/min ~13.5L/min MVVa
Less rapid deep breathing rate of 24 the equation works out:
RR 24 x VTa (VT 12 – VTd 2) x 70 = 16,800 ml/min, ~ 17 L/min MVVa.
Effectively at lower tidal volume of 8mls, the VTd to VT ratio which is the correction factor for the alveolar tidal volume (VTa) leads to a greater reduction of oxygen deliver to the working part of the lung, the alveoli. For the above examples the VTd/VT ratio at 30% reduction in the VT becomes [(12 x 0.7) – 2]/(12 x 0.7) or ~6/8 or 0.75.
The the larger VT the reduction of deliver to the alveoli (VTa) is significantly less. The formula then becomes (12 – 2)/12 or 10/12 or 0.83 or about 10% less reduction of VTa [(0.83 - 0.75)/0.83] x 100 = 9.6% or ~10%.
Your heart rate during exercise being slower with the deeper slower breathing when exercising, attests to the fact of greater oxygen being deliver to the heart and working muscles with the increased minute ventilatory volume and is testament to the physiology of the human body worked out algebraically above. So for all you readers in high school or college algebra, there are practical applications of algebra, don’t blow it off.
So the bottom line rapid shallow breathing is not as effective as slower, deeper breathing in getting more oxygen to the working part of the lungs, the alveoli.
But you have to take into account your unique physical makeup. If you find that the slower deeper breathing is more difficulty for you, then there may be some other limiting factors such as undiagnosed asthma which can be triggered by the deeper breathing. If you are trying to breathe through your nose, the rapid more shallow breathing will work more effectively with the smaller air volumes that you would be moving. This is a trick some asthma sufferers, who are not well controlled, have adapted to avoid triggering an asthma attack. If you have symptoms of chest tightness, coughing or wheezing with deep breathing especially with intense exercise, then you may well have asthma that has not been diagnosed. If you have these symptoms visit with your doctor and request a referral to a Pulmonologist who can do exercise testing to look for evidence of underlying asthma. If confirmed, you would benefit from a long term asthma controller (preventer) medication plus having available rescue bronchodilator medication.
If not asthma causing the airflow restriction, other airflow restrictive processes such as scaring to the trachea from previous injury (trauma, prolonged intubation, prior tracheostomy) or compression of the trachea from enlarged lymph nodes, vascular rings or tumor mass would be in the differential. Mechanical impediment of the diaphragm working such as from congenital or acquired diaphragm paralysis such as from previous surgery to the abdomen or chest, or trauma to the abdomen or chest or a diaphragmatic hernia could require you to breathe more rapidly. Again a visit to a Pulmonologist may help sort these differential diagnoses out.
Paul K. Nolan, MD
AKA: The Bike Doc
Last edited by The Bike Doc on Tue Aug 21, 2012 12:47 pm GMT +0000; edited 1 time in total