Respiratory Muscle Fatigue: An Overlooked Topic In Swimming?

By Sean Kao

Ventilation during swimming is an interesting topic compared to land sports because of the unique properties of water and stroke mechanics. When submerged, there is a constant hydrostatic pressure that exerts on our chest, making it harder to inhale. Secondly, the breaststroke, butterfly, and freestyle strokes require a swimmer to time their breath with their stroke.

Keeping this in mind, swimmers may be prone to inspiratory muscle fatigue (IMF). Specifically, IMF is fatigue of the muscles used during inhalation which include the external intercostals and diaphragm. IMF has been recorded in as little as 2.7 minutes in world class masters swimmers (Lomax et al. 2005), and during the front crawl with a controlled frequency breathing (Jakovljevic et al. 2009). Additionally, IMF may play a role in swimming for two reasons:

1) Increased fatigue in the inspiratory muscles may lead to deviation of blood from the working limb locomotor muscles to the inspiratory muscles.
2) Fatigued inspiratory muscles may not be able to draw a sufficient amount of oxygen into the lungs.

Inspiratory Muscles

With this being said, it may seem tempting to go out and purchase a breathing training device in an attempt to improve swimming performance. After all, a larger total lung capacity (TLC) can potentially allow you to:

• Hold more air in the lungs (become more buoyant)
• Hold your breath for a longer period of time
• Reduce inspiratory muscle fatigue
• Reduce deviation of blood from locomotive muscles to inspiratory muscles

Before you go out and purchase a breathing training device, here is some research to allow you to form your own opinion on the efficacy of the device:

Clanton et al. (1987) studied 16 Ohio State competitive swimmers for 12 weeks. 8 underwent their normal swim training while another 8 did their normal swim training + inspiratory muscle training (IMT). Upon training, both groups increased their lung function equally. The authors used vital capacity (amount of air you can exhale after full inspiration) and total lung capacity (VC+RC) to measure lung capacity. Maximal inspiratory pressure, which expresses inspiratory muscle strength, also had pre-post significant mean differences in both the test and control group (p<.005 and p<.05 respectively). Similarly, Mickleborough et al. (2008), used 30 elite swimmers and split them into 3 groups: Swim+IMT, Swim+Sham-IMT(control group), and Swim only. After 12 weeks of training they found significant increases in lung function in all three groups (p<0.05) proving that swim training alone is just as sufficient in improving lung function as using a breathing trainer. On the contrary, Kapus et al.(2013), Kilding et al.(2010), and Lemaitre et al. (2013) all showed respiratory function in the test group only. They also found that respiratory muscle training improves swimming performances compared to the control.

So what’s the difference? The three authors that found improvements in swimming performance following respiratory muscle training all used subjects that were adolescents or extremely mediocre swimmers (i.e Kilding et al. used male and female swimmers age ~19 with an average 100 SCM time of roughly 1:04). On the other hand, Mickleborough et al. and Clanton et al. used elite swimmers and found no difference. This may show that younger swimmers have potentially weaker inspiratory muscles or that mediocre level swimmers may need to improve their inspiratory muscles to improve their performance.

My recommendation would be to seek a medical professional and have them measure your lung function such as your maximal inspiratory pressure. If you fall above average or in the norm there may be no need to train your inspiratory muscles because swimming itself has been shown to improve the inspiratory muscles due to the constant hydrostatic pressure. Additionally, future cross sectional research should be conducted on elite and club swimmers in order to establish a norm for lung function, which could potentially lead to performance improvements in the general swimming population.


Clanton, T. L., Dixon, G. F., Drake, J., & Gadek, J. E. (1987). Effects of Swim Training on Lung
Volumes and Inspiratory Muscle Conditioning. The American Physiological Society.

Kapus , J. (2013). Effects of Inspiratory Muscle Training on Inspiratory Muscle Strength and
Sprint Swimming Performance in Young Female and Male Swimmers. Kinesiologia Slovenica, 53-61.

Kilding, A. E., Brown, S., & Mcconnell, A. K. (2009). Inspiratory muscle training improves 100
and 200 m swimming performance. European Journal of Applied Physiology,108(3), 505-511. doi:10.1007/s00421-009-1228-x

Lemaitre, F., Coquart, J., Chavallard, F., Castres, I., Mucci, P., Costalat, G., & Chollet, D.
(2013). Effect of Additional Respiratory Muscle Endurance Training in Young Well-Trained Swimmers . Journal of Sports Science and Medicine, 630-638.

Lomax, M., & McConnell, A. (2003). Inspiratory Muscle Fatigue in Swimmers after a Single
200m Swim . Journal of Sports Sciences, 659-664

Mickleborough, T. D., Stager, J. M., Chatham, K., Lindley, M. R., & Ionescu, A. A. (2008).
Pulmonary adaptations to swim and inspiratory muscle training. European Journal of Applied Physiology,103(6), 635-646. doi:10.1007/s00421-008-0759-x