When playing sport, you may have a weak spot, something you feel becoming fatigued before anything else. This could be your legs, lungs or your mental state collapsing. It could even be your heart and lungs struggling to meet the demands from the rest of your body.
When you compete in sport, your body prioritises blood flow to the muscles that are most used in the activity. This will often include your arms and legs, as your limbs work harder your body supplies these areas with greater blood flow to reduce fatigue. Furthermore this allows you to maintain higher levels of performance, that would otherwise be impossible if the body did not prioritise blood flow to the arms and legs.
Your sport likely places high load on your heart and lungs (high breathing and heart rate). Your respiratory muscles (muscles that control our breathing) will likely fatigue during exercise although you may not always feel it straight away. When this occurs, those muscles send signals to the brain demanding more blood flow so they can maintain performance and reduce the level of fatigue. As the brain (rightly so) prioritises our ability to breath and sustain blood flow above many other things, the brain promptly responds by increasing blood flow to your respiratory muscles.
Although keeping you breathing, it acheives this through reducing the blood flow to the peripheral muscles (muscles in your legs and arms). This has the downside of reducing the amount of work you can do; being a reduced total power output, strength and endurance before becoming fatigued. As blood flow is redirected, your active and passive recovery will clearly be reduced, meaning that an intensity that would previously be easy to maintain, will induce fatigue in the muscles faster than if those peripheral muscles continued to receive the original level of blood flow. In a competitive situation, it could result in a loss due to a reduced performance that what you would normally expect from yourself.
This domino effect can be diminished through training your respiratory muscles. The amount of redirected blood flow from your peripheral muscles to your respiratory muscles can be reduced by up to 15%. In terms of blood flow, this is significant! Training of the respiratory muscles increases their endurance and increases their threshold before fatigue, allowing you to work harder for longer before the respiratory muscles demand more blood from your brain.
If you train your breathing muscles, then your peripheral muscles can retain priority for longer, allowing you to maintain high performance for longer before succumbing to a state of fatigue and decreased performance.