There is a new Review Article in Frontiers in Physiology (January 2019) that looks into using respiratory/inspiratory muscle training for acclimatisation to altitude.
Respiratory muscle training
Respiratory muscle training, or RMT, is a programme of exercises that aim to improve the function of the respiratory muscles. Otherwise known as the ‘breathing pump’ muscles, the expiratory muscles and the inspiratory muscles make up the respiratory muscles. It's the inspiratory muscles that we use when we breathe in. The main inspiratory muscle is the diaphragm, but to a lesser extent, the intercostal muscles also help with inhalation. To help improve the strength and stamina of these inspiratory muscles, respiratory muscle training will include Inspiratory Muscle Training (IMT).
Inspiratory Muscle Training
Inspiratory muscle training, such as with POWERbreathe, uses resistance to provide the training effect. When breathing in against the resistance, the breathing muscles have to work harder. As a result, they get stronger. Consequently, breathing stamina improves resulting in a reduction in breathing fatigue. There is numerous research validating this form of breathing training and, as a result, it is the most commonly used.
For the review, researchers perform a comprehensive search, analysing seven appropriate studies. Three of these studies refer to using respiratory muscle endurance training (RME with isocapnic hyperpnea). However, the remaining four studies use respiratory muscle strength training (RMS with POWERbreathe IMT).
Acclimatisation to altitude
Studies suggest that respiratory muscle training with IMT is a useful preparatory method for enhancing respiratory muscle efficiency 4-6 weeks before being exposed to hypoxia/altitude.
It is evident that breathing during exercise in hypoxia is associated with increased energy costs (20–30%) when compared to normoxia. Therefore, it is more likely to cause respiratory muscle fatigue. However, inspiratory muscle training will help to combat this. This is because IMT trains the inspiratory muscles to become stronger, increasing stamina. Consequently, breathing muscle fatigue reduces.
It, therefore, seems apparent that breathing muscle training has the potential to minimise at least some of the limiting respiratory factors that occur during training and competition in hypoxia/at altitude.
Benefits of acclimatisation to altitude using IMT
The Review suggests that both elite athletes and non-elite individuals may benefit from RMT, including:
- A delay in the onset of premature fatigue.
- A delay in respiratory muscle metaboreflex onset/activation.
- An improvement in clearance and tolerance to anaerobic metabolite products.
- A decrease in the perception of dyspnea (‘air hunger’).
- An increase in oxygen saturation values.
- A more favourable blood redistribution to the locomotor muscles.
Finally, evidence from this review finds that respiratory muscle training is an effective stimulus for improving the strength and endurance of the respiratory muscles. In fact, it’s these adaptive responses that contribute to the improvement of ventilatory function and efficiency. In translation, this means that respiratory muscle training is very likely to improve exercise performance in normoxia and particularly in hypoxia/altitude.