Regardless of the activity, as exercise intensity increases so to does ventilation. This provides the needed oxygen to body tissues and eliminates carbon dioxide so you can work harder. Tidal volume, which is the depth of each breath, also increases—and your breathing rate becomes more rapid.
The body is built with an immense reserve capacity. During exercise, pulmonary ventilation—the volume of air inhaled and exhaled every minute—may increase from a resting value of 10 to 15 liters per minute to over 150 liters per minute.
But intense breathing efforts come at a cost. Respiratory muscles, like all other skeletal muscles, produce mechanical work and consume energy. During heavy exercise, the effort of breathing may account for more than 15 percent of total oxygen consumption. Consequently, scientists have dedicated large amounts of time and resources to exploring whether it's possible to improve the function of respiratory muscles and whether this could enhance exercise performance.
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Weight Training for Your Lungs
In 1998, Caine and McConnell conducted a study in which a group of subjects trained with a device to increase resistance to inspiration. The resistance was equivalent to 50 percent of their peak inspiratory pressure, effectively your one-rep max for breathing-in. The subjects trained for 30 breaths, twice a day for four weeks. This simple protocol increased inspiratory muscle strength by 31 percent and inspiratory muscle endurance by nearly 28 percent. (2)
Given the large workload of the inspiratory muscles, many researchers have speculated as to exactly how much these muscles contribute to the accumulation of blood lactate during intense exercise. In 2008, Brown et al. concluded that training the inspiratory muscles helped to reduce blood lactate concentrations during whole body exercise (3).
In 2012, Brown went on to test the effects of inspiratory muscle training (IMT) on blood lactate and oxygen uptake at the onset of exercise. Their conclusions suggested that IMT resulted in an increase in the oxidative and/or lactate transport capacity of the inspiratory muscles (2). So, it's clear that the inspiratory muscles can be trained and do get stronger for longer, showing improvements at oxidizing fuel and metabolizing lactate. But could this make us faster cyclists?
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Can Respiratory Muscle Training Enhance Performance?
There aren't any prizes for stronger lungs by themselves, but in 2002, Romer et al. found that IMT significantly reduced RPE (Rating of Perceived Exertion) and improved 20K and 40K cycling time trial performance, relative to a placebo (4).
In 2008, Edwards et al. set out to test whether IMT combined with cardiovascular training was more effective than cardiovascular training alone at improving 5000-meer run performance (5). Sixteen subjects completed a four-week cardio program; half of the group combined cardio with daily IMT sessions. Whilst the performance of both groups was enhanced, the IMT group's performance improved twice as much (-4.3 percent vs. -2.2 percent). Interestingly, the researchers suggested that this was likely due to the fact that IMT significantly reduced the subject's RPE during the performance test.
Make It Feel Easier—Go Faster!
RPE is strongly associated with exercise performance. If you can make it feel easier, you'll probably go faster! Historically, physiological research has been based on the assumption that fatigue is mainly a result of running out of energy and/or metabolites accumulating (e.g. blood lactate). However, increasing evidence is pointing to the brain as a central limiter, reducing our performance long before energy reserves run out or the tissues experience a chemical catastrophe (6,7).
To suggest that fatigue is mediated by either brain or body in entirety is a false dichotomy; it's likely a combination of both, but in the context of IMT, the fact that this form of training can make exercise feel easier may be its greatest gift to enhancing human performance.
If the brain perceives that an effort is easier, it will allow the muscles to work harder. In the 2008 Edwards study, the fact the IMT significantly reduced RPE during extended high-intensity exercise should be of great interest to athletes at all levels.
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How Can You Do It?
So if you want to improve your performance through IMT, what's the most effective way to do it? To start with, you need to purchase some kind of inspiratory muscle training device. These devices provide resistance to load the inspiratory muscles when breathing. As your strength increases the load can be increased proportionally to facilitate progression.
With units starting at around $35, it's a very cost effective entry point into the world of IMT. Numerous studies have demonstrated that a simple protocol of 30 breaths, twice daily for four to 12 weeks followed by a maintenance period in which training is reduced by two-thirds can significantly improve the strength and endurance of respiratory muscles associated with enhanced endurance performance and reduced RPE (8).
IMT During Exercise
Less well known is the use of IMT while exercising. In 2013, Hellyer et al. conducted a study involving 10 subjects carrying out IMT at 40 percent maximal inspiratory pressure while simultaneously performing aerobic exercise (cycling). Activity in the respiratory muscles significantly increased (measured with EMG) relative to performing IMT in isolation. These results suggest that combining IMT with cycling may significantly enhance its training effect (9).
This kind of training could be carried out by determining a 'one-rep max' with a PowerBreathe, before carrying out the 30 breath protocol at 40 percent while riding on a stationary trainer, exercise or spin bike, or before a conventional training session.
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The Final Breath
Some takeaway points:
1. During heavy exercise, pulmonary ventilation may increase by 600 percent or greater.
2. Breathing may account for more than 15 percent of total oxygen consumption.
3. Inspiratory muscles can be trained, resulting in increased strength, endurance, reduced blood lactate concentration and RPE.
4. A simple protocol of 30 breaths, twice daily is sufficient to significantly improve performance.
5. More advanced trainers may wish to experiment with using IMT during aerobic exercise to enhance the training effect.
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