Train the diaphragm to improve cardio training
Do you become breathless early when running, cycling or doing other forms of cardio training, even though your legs still have more to give? Then breathing may be the limiting factor. How you breathe plays a crucial role in your cardiovascular fitness, endurance and ability to improve your VO2 max.
The diaphragm – the body’s most important breathing muscle
The diaphragm is the body’s primary breathing muscle and is responsible for the majority of ventilation during both rest and physical activity. Located beneath the lungs, it enables deep and efficient breathing by moving down during inhalation and up during exhalation.
When cardiovascular training begins, the demands on the diaphragm’s strength, endurance and ability to cope with high ventilatory load increase significantly. A well functioning diaphragm therefore becomes a decisive factor for both endurance and physical performance.
Read more about how the diaphragm works.
Why breathing can limit cardiovascular fitness
Many people who train cardio experience breathing strain long before their leg muscles are fatigued. This is a common sign that the respiratory muscles, particularly the diaphragm, are not fully meeting the increased demands that arise as intensity increases.
When the diaphragm works more efficiently, each breath delivers improved oxygen exchange. Breathing feels calmer, heart rate becomes more controlled and perceived exertion is more evenly distributed during running and other cardiovascular activities.
As pace increases, the body needs to:
- take in more oxygen
- eliminate more carbon dioxide
- maintain efficient breathing under load
If the diaphragm cannot work effectively, breathing often becomes rapid and shallow. This reduces oxygen uptake and makes training feel harder than it actually is. As a result, you may feel breathless earlier, even though your legs still have capacity.
What happens when the respiratory muscles become fatigued?
Research shows that respiratory muscles can become fatigued under high load, even in well trained individuals. When this occurs, breathing efficiency decreases and perceived exertion increases.
When respiratory muscles fatigue, the body may redistribute blood flow to support breathing. This can reduce the available capacity for working leg muscles, meaning that breathing rather than muscle strength becomes the limiting factor for performance.
When the diaphragm functions more efficiently, breathing feels calmer, heart rate is more controlled and workload feels more evenly distributed during cardiovascular training.
What does research say about diaphragm training?
Scientific studies show that respiratory muscles, including the diaphragm, respond to training in the same way as other skeletal muscles. With regular and targeted loading, both strength and endurance can be improved.
Research has shown benefits such as:
- reduced sensation of breathlessness during physical exertion
- more stable and controlled breathing during training
- improved endurance during everyday activity and cardio exercise
- faster recovery between work intervals
- a more positive and controlled training experience
These effects are linked to improved diaphragm endurance and increased tolerance to ventilatory load. For many recreational athletes, this makes it easier to maintain a steady pace and train for longer with better breathing control.
Can the diaphragm be trained?
Yes. The diaphragm is a skeletal muscle and can be trained, just like other muscles in the body. Although running and other forms of cardio training place demands on the respiratory system, they are not always sufficient to optimise diaphragm capacity.
Specific diaphragm training with controlled resistance can therefore be an effective complement to cardiovascular training.
How do you train the diaphragm to improve fitness?
Effective diaphragm training is based on:
- controlled activation of the respiratory muscles
- resistance during inhalation and exhalation
- short, repeated training sessions
The aim is to increase diaphragm strength and endurance so it can work more efficiently under high load.
Breathing exercises
Simple exercises focusing on calm, deep breathing can help improve diaphragm activation.
Neuromuscular training
IQoro is a neuromuscular training device used as a complement to other forms of exercise. Through controlled resistance, muscles in the mouth, pharynx and diaphragm are activated. These muscles are functionally linked to breathing and posture.
For recreational athletes, this can contribute to improved breathing control and endurance. The training is low intensity, time efficient and easy to integrate into daily routines, 3 x 30 seconds, three times per day.
Studies have also shown positive effects of IQoro training for conditions such as reflux, swallowing function and postural control. In these studies, 97 percent of participants showed significant improvement, and many are completely free from symptoms today.
FAQ – questions and answers
The diaphragm is the primary breathing muscle and controls how efficiently air moves in and out of the lungs. During cardio training, a strong diaphragm helps the body take up more oxygen, reduce breathlessness and maintain endurance at higher intensities
Breathlessness is not always caused by low fitness. If the diaphragm does not work efficiently, breathing becomes shallower, leading to reduced oxygen uptake and earlier fatigue, even in well trained individuals.
Yes. The diaphragm is a skeletal muscle and can be trained specifically. Diaphragm training involves controlled activation with resistance and regular practice, similar to other forms of muscle training.
Studies show that respiratory muscle training can reduce perceived exertion and improve endurance during cardiovascular exercise. These improvements are linked to more efficient breathing and better oxygen utilisation.
Diaphragm training is most effective when performed regularly in short sessions. It should be viewed as a complement to cardio training and integrated into daily routines.
Chest breathing is shallower and primarily engages the upper lungs. Diaphragmatic breathing activates the diaphragm, enabling deeper breathing, improved oxygen uptake and better breathing control during physical exertion.
Text by: Mary Hägg
Associate Professor of Experimental Research in Ear, Nose and Throat diseases at Uppsala University, and Hospital Dental Surgeon specializing in orofacial medicine.
Mary has worked for 12 years as a hospital dentist and for 31 years as Head of the Speech & Swallowing Centre, Department of Otorhinolaryngology, Hudiksvall Hospital, Sweden.
Scientific references
- Illi SK, Held U, Frank I, Spengler CM. Effect of respiratory muscle training on exercise performance in healthy individuals. European Journal of Applied Physiology. 2012. https://pubmed.ncbi.nlm.nih.gov/29985221/
- McConnell AK. Respiratory muscle training as an ergogenic aid. Respiratory Physiology & Neurobiology. 2013. https://pubmed.ncbi.nlm.nih.gov/30261349/
- Janssens L et al. The impact of inspiratory muscle fatigue on exercise performance. Sports Medicine. 2013. https://pubmed.ncbi.nlm.nih.gov/29249083/
- Sheel AW et al. Respiratory muscle training and exercise performance. Journal of Applied Physiology. 2020. https://pubmed.ncbi.nlm.nih.gov/33467421/
- Hägg M, Tibbling L, Franzén T. Esophageal dysphagia and reflux symptoms before and after oral IQoro® training. World Journal of Gastroenterology. 2015;21(24):7558–7562. Open access.
- Hägg M, Tibbling L. Effect of IQoro® training on impaired postural control and oropharyngeal motor function in patients with dysphagia after stroke. Acta Otolaryngologica. 2016;136(7):742–748. DOI:10.3109/00016489.2016.1145797.