Aerobic Fitness Effects On Exercise-Induced Low-Frequency Diaphragm Fatigue

“Bilateral phrenic nerve stimulation was used to compare the amount of exercise-induced diaphragm fatigue between two groups of healthy subjects, a high-fit group and a fit group.”


“The high-fit subjects showed diaphragm fatigue as a result of heavy endurance exercise but were also partially protected from excessive fatigue, despite high ventilatory requirements, because their hyperventilatory response to endurance exercise was reduced, their diaphragm was utilized less in providing the total ventilatory response, and possibly their diaphragm aerobic capacity was greater.”

Read Aerobic fitness effects on exercise-induced low-frequency diaphragm fatigue >

IMT Enhances Pulmonary O2 Uptake Kinetics And High-Intensity Exercise Tolerance In Humans

Fatigue of the respiratory muscles during intense exercise might compromise leg blood flow, thereby constraining oxygen uptake ( O2) and limiting exercise tolerance. This study tested the hypothesis that inspiratory muscle training (IMT) would reduce inspiratory muscle fatigue, speed O2 kinetics and enhance exercise tolerance.


“Specific training of the inspiratory muscles increased baseline MIP, reduced estimated inspiratory muscle fatigue during severe and maximal-intensity exercise, and enhanced O2 dynamics and exercise tolerance…

“Pressure-threshold IMT appears to present a practical and efficacious means for modulating the O2 response to high-intensity exercise in healthy young people…”

“IMT therefore appears to have considerable potential as an adjunct to physical training for the enhancement of exercise performance.”

Read IMT enhances pulmonary O2 uptake kinetics and high-intensity exercise tolerance in humans >

How The Inspiratory Muscles Contribute To The Breathing Process

The diaphragm and chest wall muscles act together like a bellows to pump air in and out of the chest.

To breathe in these muscles contract to expand the chest cavity, causing a pressure drop into which the air flows. To breathe out, you simply relax these ‘inspiratory’ muscles and the chest springs back forcing the air out of your lungs.

During exercise the exhalation is assisted by contraction of the abdominal muscles and the inspiratory muscles undertake most of the work of breathing.

In contrast to observations of inspiratory muscle fatigue, research has not yet identified exercise-induced expiratory muscle fatigue which is why, until there is sufficient evidence to prove otherwise, it would be unnecessary to train anything other than the inspiratory muscles.

Also, while 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.

Scientific studies show that by exercising your inspiratory muscles with POWERbreathe you will increase the strength and stamina of your breathing muscles, reducing inspiratory fatigue and improving your performance.

Track running induces inspiratory muscle fatigue in trained runners

A study published in The Journal of Strength and Conditioning Research (September 26th 2015) tested the hypothesis that short-duration running exercise would induce Inspiratory Muscle Fatigue (IMF) which may limit performance. This follows studies that found IMF occurs after short-duration swimming exercise.

Eight female middle-distance runners were the subjects of this study which found that IMF does occur after short-duration running exercise.


“Coaches could consider prescribing inspiratory muscle training or warm-up in an effort to reduce the inevitable IMF associated with maximal effort running.”


400-meter and 800-meter track running induces inspiratory muscle fatigue in trained female middle-distance runners.

Effects of IMT on Resistance to Fatigue of Respiratory Muscles in Exercise

EliteVelo Kalas Sportswear Cycling Race Team by Richard Fox Photography

EliteVelo Kalas Sportswear Cycling Race Team using POWERbreathe Plus IMT (above)
PHOTO: Richard Fox Photography


Effects of Inspiratory Muscle Training on Resistance to Fatigue of Respiratory Muscles During Exhaustive Exercise
M. O. Segizbaeva, N. N. Timofeev, Zh. A. Donina, E. N. Kur’yanovich, N. P. Aleksandrova

This study, published in Body Metabolism and Exercise – Advances in Experimental Medicine and Biology (Volume 840, 2015, pp 35-43) concluded that IMT elicits resistance to the development of inspiratory muscles fatigue during high-intensity exercise.


To assess the effect of inspiratory muscle training (IMT) on resistance to fatigue of the diaphragm, parasternal, sternocleidomastoid and scalene muscles in healthy humans during exhaustive exercise.

The sternocleidomastoid muscle flexes the neck and helps with the oblique rotation of the head. Also, the muscle helps in forced inspiration while breathing, and it raises the sternum. As for forced inspiration, the muscle also works in concert with the scalene muscles in the neck. The scalene muscles are lateral vertebral muscles that begin at the first and second ribs and pass up into the sides of the neck. There are three of these muscles. (SOURCE:


“The study found that in healthy subjects, IMT results in significant increase in MIP (+18 %), a delay of inspiratory muscle fatigue during exhaustive exercise, and a significant improvement in maximal work performance. We conclude that the IMT elicits resistance to the development of inspiratory muscles fatigue during high-intensity exercise.”

Read Effects of Inspiratory Muscle Training on Resistance to Fatigue of Respiratory Muscles During Exhaustive Exercise

Check out more Inspiratory Muscle Training Research here >

Discover POWERbreathe used in Research here >

Locomotor & diaphragm muscle fatigue in endurance athletes

Published in the European Journal of Applied Physiology (August 2014, Volume 114, Issue 8, pp 1619-1633).


Locomotor and diaphragm muscle fatigue in endurance athletes performing time-trials of different durations
Thomas U. Wüthrich, Elisabeth C. Eberle, Christina M. Spengler


“Fatigue in leg muscles might differ between running and cycling due to inherent differences in muscle activation patterns. Moreover, postural demand placed upon the diaphragm during running could augment the development of diaphragm fatigue.”


“We investigated quadriceps and diaphragm fatigue in 11 runners and 11 cyclists.”


“Different levels of leg muscle fatigue in runners and cyclists could in part be related to the specific muscle activation patterns including concentric contractions in both modalities but eccentric contractions in runners only. Diaphragm fatigue likely resulted from the large ventilatory load which is characteristic for both exercise modalities and which was higher in 15TTs than in 30TTs (+27 %, p < 0.01) while postural demand appears to be of less importance.”

Thankfully there is something you can do to help alleviate diaphragm fatigue. Like any other muscle group you can train your breathing muscles (which includes your diaphragm) with POWERbreathe Inspiratory Muscle Training. Click on the links below to find out more about:

View the Abstract here

View list of published research that used POWERbreathe as the IMT intervention of choice in POWERbreathe in Research.

Find more published research on our Inspiratory Muscle Training Research blog.

Breathing Muscle Fatigue in Swimming – POWERbreathe Could Help

Dr Mitch Lomax, Sport and Exercise Scientist and Senior Lecturer in Sport and Exercise Physiology at the University of Portsmouth, gave an interview to Swimming Science in which she discussed her investigation into the breathing demands of swimming and the discovery that the occurrence and consequences of breathing muscle fatigue in swimming had been overlooked.

In the interview Dr Lomax goes on to explain how in her study they found that Inspiratory Muscle Fatigue (IMF) occurs in all swimming strokes. Surprisingly being very fit does not prevent it, and as the amount of inspiratory muscle fatigue in trained swimmers can exceed 19%, a faster rate of limb muscle fatigue is also a real possibility.

Dr Lomax’s take home message from her study is that “IMF occurs during swimming, even in very well trained swimmers. It can negatively affect stroke characteristics, and has the potential to speed up the occurrence of limb muscle fatigue. The good news is that we can do something about it.”

So what can be done about it? Well Dr Lomax goes on to say that clearly swim training alone is not sufficient to protect against IMF, so “Targeted training of these muscles is my advice i.e. inspiratory muscle training (IMT).”

POWERbreathe inspiratory muscle training specifically targets the breathing muscles, strengthening them by around 30-50%, significantly improving performance and helping to eliminate breathing fatigue.

Read the full Friday Interview on Swimming Science.

Dr Lomax’s main research centres upon the pulmonary limitations to exercise and the impact of respiratory muscle training on performance with a particular focus on swimmers, and you can view her Research Articles here.

Read more about why you should consider incorporating POWERbreathe inspiratory muscle training as part of your swimming training, and if you’re already using POWERbreathe as part of your training, then please leave a comment here or on the POWERbreathe Forum, Facebook or Twitter as we’d love to hear from you. You can also read more about using POWERbreathe in swimming training in our Swimming Blog.


Inspiratory Muscle Fatigue Affects Broadest Muscle in the Back During Front Crawl

A paper was published online in the Journal of Strength and Conditioning Research that revealed how “the presence of inspiratory muscle fatigue affects the activity of the latissimus dorsi during front crawl sprinting.”


Inspiratory muscle fatigue affects latissimus dorsi but not pectoralis major activity during arms only front crawl sprinting
Lomax M, Tasker L, Bostanci O.

Purpose of the study:

“To determine whether inspiratory muscle fatigue affects the muscle activity of the latissimus dorsi and pectoralis major during maximal arms only front crawl swimming.”


“…the presence of inspiratory muscle fatigue affects the activity of the latissimus dorsi during front crawl sprinting.”

Read the Abstract on PubMed.