Physician Led • Outcomes Centered • Patient Focused

Improve Your Endurance with Inspiratory Muscle Training

In most cases, an athlete’s ability to exercise is limited by the heart’s ability to pump blood to the muscles – not the lung’s ability to deliver oxygen to the heart.  Despite this, breathlessness can often limit exercise performance. This breathlessness doesn’t relate to problems with air transport, but instead to fatigue of the respiratory muscles themselves – the diaphragm, intercostal muscles and the accessory muscles around the neck which assist with chest wall expansion during breathing.  When we breathe, our airways generate airflow resistance that our breathing pump must work to overcome.  The stronger the pump, the easier it is to overcome this air resistance and the easier the sensation of breathing is.

The demands on the lungs increase significantly during exercise – particularly in late stages of exercise when the body is producing more lactic acid since lactic acid is converted to water and carbon dioxide – the latter being eliminated through ventilation.  When we do exercise testing on patients in our office, it is not unusual to see an increase from about 7.5-10 liters of air breathed/minute at rest, to 150-200 liters/minute during maximal exercise.  Rarely, elite athletes can increase their ventilation to 300 liters/minute!  Obviously, this places a significant stress on the muscles responsible for respiration, and these muscles are prone to fatigue just like other muscles in the body.   The harder the lungs work, the more blood flow they require, “robbing” blood from working limbs.  It has been estimated that in late exercise, about 16% of oxygen consumption is used in order to power breathing.  Research has shown that to effectively train respiratory muscles to better adapt to these higher ventilation levels, a training load that approximates ventilation during intense exercise needs to be imposed.  Makes sense, doesn’t it?

So what does training of the respiratory muscles accomplish? First of all, strength training results in measurable structural changes.  Ultrasound-based measurements of the diaphragm before and after 4-8 weeks of training show, on average, a 12% increase in thickness.  After four and eight weeks of training, inspiratory muscle strength improved by 24% and 41%, respectively.  Peak inspiratory flow rates and maximal power of the lungs have been shown to improve as well.

But what does this mean for performance? Multiple studies have measured the effect of inspiratory muscle training (IMT) on performance in various endurance sports.  Those in cycling have shown average improvements of 2.6-4.6% in time trial events ranging from 20 to 40 km in length.  To translate this into real world numbers, I went to the 2012 results of the Hy-Vee Triathlon, men’s elite division.  Factoring in a 4.6% reduction in cycle time would have improved Aussie John Amberger’s 6th place finishing time by 2 minutes and 41 seconds and put him into 1st place.

Similar studies looking at changes in performance:

  • Cycling:  2.6-4.6% improvements in 20-40K time trials
  • Running:  2% improvement in 5K split time
  • Rowing:  1.9-2.7% improvement in 6-20 minute time trials
  • Soccer-specific performance test:  17% improvement
  • Swimming:  1.5-1.7% improvement in 100-200 m swim performance.
  • Altitude-sports:
    • 25% reduction in the breathing requirement of exercise
    • 14% reduction in the cardiac output requirement of exercise
  • Reduction of symptoms of exercise-induced asthma or vocal cord dysfunction.
  • Triathlon:  See above for component improvements.  In addition, the work of breathing is lessened when:
    • Swimming in wetsuits
    • Riding in aero position

So, IMT unquestionably can help improve endurance performance.  Studies looking at the effect of IMT on other sports are also encouraging.  Two studies looking at performance on a yo-yo sprint test (designed as a soccer-specific test, but also applicable to football, rugby, basketball, and tennis) before and after IMT, showed improvements of 17% over baseline.  Finally, IMT clearly improves exercise tolerance at altitude.  Four weeks of IMT improved the breathing requirement of exercise at 12,000 feet by 25% and reduced the oxygen requirement 8-12%.

Here’s where things get more interesting. Because the inspiratory muscles have extensive attachments around the spine, strengthening them also improves core stability significantly.  Thus, the potential benefits of IMT also include:

  • Reduction of side stitches with running.
  • Reduction of low back pain in cyclists and runners.
  • Improved breathing efficiency in the aero position during cycling.
  • Improved power production for rowers and swimmers.
  • Improved maintenance of core stability late in gameplay (ex:  tennis, basketball, soccer, football).
  • Reduced risk of back injury in late exercise when an athlete is most fatigued.

Because of the effect of IMT on the core, IMT can be progressively moved from exercises performed in a standing posture to being incorporated into more sport-specific functional exercises.  This also has implications for therapy in patients with low back pain or lower extremity overuse problems that can be attributed to core instability.  Integrating IMT into a monitored physical therapy program can pay dividends both in terms of injury recovery and ultimately performance improvement.

Finally, IMT has been shown to significantly improve symptoms associated with conditions that affect breathing, such as vocal cord dysfunction, exercise-induced asthma, and cystic fibrosis.  Incorporating IMT into the exercise routines of these patients can dramatically improve overall exercise capacity.

Stadia Sports Medicine has invested in the latest IMT technology, with the capability of measuring both individual and team improvements in lung function before and after respiratory training.  Training can be focused on a goal of strength improvement or endurance improvement.  For less than $100, we also have the ability to help patients incorporate IMT into their regular workout sessions, and can incorporate IMT into standard athletic rehabilitation when applicable.  For more information on harnessing the power of IMT into your own workouts, call our office (515-221-1102) for a consultation.

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