Inspiratory Muscle Training
by Rob Harvey
We all accept that resistance work for our arms, legs, shoulders or back is an important part of our triathlon training regimes and can help prevent injury and benefit performance, but what about resistance work for the respiratory muscles? Inspiratory Muscle Training (IMT) has received a lot of press since it first began to appear in the late 1980's. Much of the work has been pioneered by Dr Alison McConnell originally at the University of Birmingham who has always battled against the general consensus that the respiratory system can handle the load presented to it during exercise.
How do you breathe?
First it is important to understand how you breathe? The example below should help you understand the principles behind respiration:
Take a sealed glass jar. This represents your chest cavity. Replace the glass bottom of the jar with a thin rubber membrane; this represents your diaphragm muscle. Suspended inside the jar are two balloons connected to a pipe that pokes through the bung at the top of the jar. These are your lung and windpipe. As the plastic membrane of the jar is pulled down as happens when breathing, the internal volume of the jar increases. This lowers the air pressure within the jar and consequently air rushes into the balloons through the tube and they inflate. When the plastic membrane is released, as happens when your breath out, the pressure within the jar temporarily increases, air rushes out and the balloons return to their original size.
During inspiration in humans the chest cavity increases in size because of the contraction of the bell shaped diaphragm muscle and also due to the rising of the ribs due to contraction of the scalene and the external intercostal muscles. Expiration, a predominantly passive process, results from the recoil of the diaphragm and relaxation of the intercostal muscles. During exercise the exhalation is assisted by contraction of the abdominal muscles.
Does breathing limit your performance?
At rest you breathe around 12 litres of air per minute, but during heavy exercise this can rise to over 150 litres per minute, and in elite athletes, this can be as high as 220 litres, so it is clear that the ventilatory system is put under considerable stress during exercise, but does ventilation limit performance?
NO: Exercise at extreme altitudes has resulted in some of the highest recorded values (JR Sutton, Reeves et al 1988). This possibility has led Tim Noakes to suggest that humans may have ventilatory reserves when exercising at sea level, therefore in healthy individual's ventilation may not be limiting to performance. He also points out that since arterial oxygen partial pressure (PaO2 - the amount of oxygen in blood leaving the lungs) does not usually fall during maximal exercise, this indicates that the lungs continue to function correctly.
YES: The inspiratory muscles undertake most of the work of breathing. Fatigue of the inspiratory muscles has frequently been observed during exercise of short duration, high intensity exercise (Bye et al 1984) and more prolonged exercise such as marathon running (Loke et al 1982) which indicates that training of the ventilatory muscles by methods other than swim, bike and run may be beneficial to performance.
Inspiratory Muscle Training
Inspiratory Muscle Training involves using a device such as a PowerBreathe to increase the resistance you inhale against whilst allowing you to exhale freely. By progressively increasing the resistance over time the strength of your respiratory muscles can be improved. PowerBreathe's have been shown to be effective in increasing inspiratory muscle strength by 30-50% with a little as 30 breaths twice a day. Alison McConnell the pioneer of the IMT technique claims that improvements in cycling time trial performance of up to 4.6% are possible after only 6 weeks of use (that's could be 2 mins off your 40km time trial performance)!
How might IMT improve performance?
- By preventing fatigue of the inspiratory muscles blood flow to the working muscles is not redirected to the inspiratory muscles. This preserves limb blood flow and reduces reliance upon anaerobic metabolism.
- Increasing the aerobic capacity of the inspiratory muscles, making them more efficient during and after exercise.
In healthy trained individuals it seem likely that this increased ‘efficiency' of the inspiratory muscles could account for the increase in performance. Here are some other considerations when considering IMT's effect on performance:
- When running, the breathing muscles are not only working to enable you to breathe, they are also working to stabilise the upper body (especially during the foot strike when large destabilising forces are transmitted up the body). This is one of the reasons that synchronising your breathing to your running cadence is more efficient, and more comfortable, because it prevents the stabilising and breathing functions of your breathing muscles from competing.
- The hunched position adopted during cycling is a double-edged sword for the cyclist. On the one hand, it enhances aerodynamics, but on the other, it can create breathing problems. When you are hunched forward, the contents of your abdomen (mainly your liver and gut) become compressed and pushed up against your main breathing muscle, the diaphragm. This restricts its normal movement and can make breathing feel much harder. On the plus side, the upper body is supported and this means that the other breathing muscles can ‘concentrate' on breathing, not stabilising the upper body as they do when you are running.
- When swimming your breathing has to be synchronized with your stroke and you have to inhale as much as possible in the shortest time possible so that you can return your body to its optimal position for generating propulsive force. This creates an enormous strain on the inspiratory muscles and it is no surprise to find that swimmers experience significant fatigue of these muscles.
The respiratory system may represent the weak link in the oxygen transport system individuals with chronic obstructive pulmonary disease (COPD) such as asthma or emphysema. Inspiratory muscle training has been shown to relieve the symptoms of asthma by improving lung function, resulting in reduction of medication and a fall in hospitalizations (Weiner et al., 1992).
Time efficient Training?
One of the advantages of IMT is that it is very time efficient and can be added on top of your existing training load without having to make decisions about substituting it for existing training. The recommended prescription for IMT is 30 breaths twice per day taking approximately 3 minutes per set, a total of 6 mins per day. The kit is relatively cheap and very portable meaning training can be undertaken anywhere you are. The resistance required should be large enough to cause failure at 30 breaths or slightly before. Once 30 can be completed comfortably then the resistance needs to be increased.
Using IMT during your warm-up?
Volianitis et al (2001) undertook a study into the effect if a specific respiratory warm-up on rowing performance. The purpose of this study was:
- To compare the effect of three different warm-up protocols upon rowing performance and perception of dyspnoea
- To identify the functional significance of a respiratory warm-up
A group of well-trained club rowers performed a 6-min all-out rowing simulation. The researchers examined the differences in mean power output under three different conditions:
- After a sub-maximal rowing warm-up
- A specific rowing warm-up
- A specific rowing warm-up with the addition of a respiratory warm-up protocol
Mean power output during the 6-min all-out rowing effort increased by 1.2% after warm-up 3 compared with warm-up 2 which in turn, was by 3.2% higher than the performance following warm-up 1.
This suggests that a combination of a respiratory warm-up protocol together with a specific rowing warm-up is more effective than a specific rowing warm-up or a sub-maximal warm-up alone as a preparation for rowing performance. For triathlon it would be interesting to see if this also applied to swim performance.
As a warm-up to exercise or competition try the following IMT protocol:
Complete 2 x 30 breaths with a 2 mins recovery between using a setting 3, 2 or 1 settings below your normal training session value.
- Decrease resistance by 3 if you are using setting 8, 9 or 10.
- Decrease resistance by 2 if you are using 7, 6 or 5.
- Decrease resistance by 1 if you are using 4, 3 or 2.
Using IMT during your cool-down?
Researchers at the University of Sao Paulo in Brazil 9 have found that breathing against a small inspiratory load immediately after exercise reduces lactate by 16%. What's more, unlike a normal active recovery, which takes around 5-minutes to speed-up lactate clearance, inspiratory loading reduces lactate as soon as exercise stops. Furthermore, when using the inspiratory load, lactate concentration after just 5-minutes was equivalent to that achieved in 15-minutes during passive recovery.