We all do a lot of training: we ride our bikes, and we do strength work to do everything we can to get fitter, faster and stronger. From that burning sensation in the legs as we suffer our way through these training sessions, we know that we’re making them stronger and more resilient. But are we neglecting another very important muscle group?
One of the biggest factors in cycling performance is our aerobic performance, which is powered by the capacity to extract and utilise oxygen from the air that we breathe. And what do we use to extract this oxygen? Our lungs! The lungs are a brilliant system; they work without us even thinking about it and react to both environmental and chemical factors in the body. But, when we perform higher intensity or maximal capacity aerobic exercise, our lungs need to work very hard. Our normal breathing is un-laboured, doesn’t require the full capacity of our lungs and happens due to pressure differential. When breathing heavily during exercise, we are forcibly breathing. This requires us using our respiratory muscles (the diaphragm, the rib cage muscles including the intercostals & parasternals, the scalene, the neck muscles) at a greater capacity than we usually do.
Figure 1: From Thoracic Spine Major Muscles - Physiopedia
Multiple studies have found that, during prolonged endurance exercise, the respiratory muscles do experience fatigue (Aliverti, 2016). This happens due to the increased oxygen demands of these muscles when breathing heavily and risks their function being impaired due to fatigue. However, the body has a very clever mechanism to preserve respiratory function using something called the metaboreflex. This mechanism detects when oxygen demands of the respiratory muscles increase, and diverts blood flow from the locomotor muscles (primarily legs when cycling) towards the respiratory muscles instead. Essentially, when our respiratory muscles get fatigued, our body diverts the blood from our legs leading to an increased feeling of fatigue in them.
So what can we do about it? Multiple studies have found that respiratory muscle training (RMT) can improve respiratory muscle function, functional lung capacity, and resistance to fatigue (endurance) of the respiratory muscles (Sheel, 2002). One method of doing this is using a respiratory muscle trainer (previously termed ‘altitude mask’). Focussed breathing exercises can also be done, taking deep and controlled breaths utilising as much of the functional lung capacity as possible. Voluntary isocapnic hyperpnoea (VIH) is one method of doing this that requires a high level of ventilation for 30 minutes and is a very demanding training session.
Interestingly, some studies have found that RMT is more beneficial for those that are newer to exercise (Illi et al., 2012). A potential reason for this could be that, as people exercise more and fatigue their respiratory muscles more often in training, they do develop a greater endurance capacity and resistance to fatigue in the respiratory muscles. So, although RMT has been found to be beneficial for athletes looking to improve their aerobic endurance capacity, there may be RMT benefits to doing more aerobic and high intensity training. Therefore, RMT-focussed sessions may not be wholly necessary and the cycle training should be the key focus. But adding RMT into your training regime could improve your aerobic capacity at a faster rate than just cycle training by itself.
A study on RMT that I did at university can be found following this link: Google Drive: Sign-in (The effect of loaded breathing on physiological markers and effort perception during cycle ergometry)
Aliverti, A. (2016). The respiratory muscles during exercise. Breathe , 12 (2), 165-168.
Sheel, A. W. (2002). Respiratory muscle training in healthy individuals. Sports Medicine , 32 (9), 567-581.
Illi, S. K., Held, U., Frank, I., & Spengler, C. M. (2012). Effect of respiratory muscle training on exercise performance in healthy individuals. Sports medicine , 42 (8), 707-724.