Respiratory Muscle-Induced Metaboreflex

A recent research paper in Experimental Physiology looks into the effect of an increase in inspiratory muscle work on blood flow to inactive and active limbs. It addresses the process of metaboreflex.

What is metaboreflex?

Metaboreflex is where the body restricts blood flow to the limbs when the breathing muscles fatigue. The body will do this to ensure the role of breathing continues. This is because breathing is crucial to survival. Therefore, when the body experiences a conflict between breathing and moving, breathing wins out.

How does metaboreflex work?

As soon as the body senses a conflict between breathing and extreme activity, it will redirect blood flow to the breathing muscles, for survival. In so doing, blood flow to the exercising limbs shuts down, allowing the diaphragm a chance to recover. What this tells us is that the stronger the diaphragm is, the faster it will recover. Consequently, stronger breathing muscles will, in turn, result in a better blood supply to your working limbs. This will result in a better sports performance.

These YouTube videos from breathing expert James Fletcher, clearly demonstrate the metaboreflex.

Part 1

Part 2

Study results

When exercising, the amount of energy consumed by the working muscles can be high and prolonged. Blood flow to these working muscles needs to be matched. The results of this study suggest that the control of blood redistribution to the working muscles is facilitated, in part, by respiratory muscle-induced metaboreflex.

Delaying the onset of metaboreflex

Improving the strength of your breathing muscles will help to delay the onset of the metaboreflex for the diaphragm. A scientifically proven way of doing this is with Inspiratory Muscle Training (IMT). In fact, there are other studies showing IMT to be beneficial too.

This award-winning research, awarded by the European College of Sport Science (ECSS), also suggests the potential role of IMT to reduce inspiratory muscle metaboreflex.

Another study suggests respiratory muscle training could enhance sports performance by delaying this process.

Finally, there is a study by Germain Fernandez Monterrubio, Bachelor of Science in Physical Activity and Sport, in which he finds how respiratory muscle fatigue can affect exercise tolerance on a pulmonary level, as well as, a muscular level.

Effect of increased inspiratory muscle work on blood flow to inactive and active limbs during submaximal dynamic exercise >

Effects of work of breathing on blood flow during exercise

Published in Experimental Physiology this research sought to simultaneously assess leg and respiratory muscle blood flow during intense exercise while manipulating the work of breathing (WOB).

Researchers from Canada & Brazil hypothesised:

  1. Increasing the work of breathing would increase respiratory muscle blood flow and decrease leg blood flow.
  2. Decreasing the work of breathing would decrease respiratory muscle blood flow and increase leg blood flow.

The work of breathing (WOB)

Changes in work of breathing are significantly and positively related to changes in respiratory muscle blood flow. By which it shows that increasing the work of breathing increases blood flow.

On the other hand, changes in work of breathing are inversely related to changes in locomotor blood flow. So decreasing the work of breathing increases locomotor blood flow.

Study findings

Therefore findings from the study support the concept that respiratory muscle work significantly influences the distribution of blood flow to both respiratory and locomotor muscles.

The study

Effects of respiratory muscle work on respiratory and locomotor blood flow during exercise >

Attenuated Inspiratory Muscle Metaboreflex In Endurance-Trained Individuals

“The inspiratory metaboreflex is activated during loaded breathing to task failure and induces sympathetic activation and peripheral vasoconstriction that may limit exercise performance. Inspiratory muscle training appears to attenuate the inspiratory metaboreflex in healthy subjects. Since whole body aerobic exercise training improves breathing endurance and inspiratory muscle strength, we hypothesized that endurance-trained individuals would demonstrate a blunted inspiratory muscle metaboreflex in comparison to sedentary individuals.”

Conclusion:

“Data demonstrate that endurance-trained individuals have an attenuated inspiratory muscle metaboreflex.”

Read Attenuated inspiratory muscle metaboreflex in endurance-trained individuals >

The Influence Of Inspiratory Muscle Work History And Specific IMT Upon Human Limb Muscle Fatigue

“The purpose of this study was to assess the influence of the work history of the inspiratory muscles upon the fatigue characteristics of the plantar flexors. It was hypothesized that under conditions where the inspiratory muscle metaboreflex has been elicited, plantar flexors fatigue would be hastened due to peripheral vasoconstriction.”

Conclusion:

“The data are the first to provide evidence that the inspiratory muscle metaboreflex accelerates the rate of calf fatigue during plantar flexors, and that inspiratory muscle training attenuates this effect.”

Read The influence of inspiratory muscle work history and specific inspiratory muscle training upon human limb muscle fatigue >

Acute Cardiorespiratory Responses To Inspiratory Pressure Threshold Loading

“The purpose of this study was to test the acute responses to differing pressure threshold inspiratory loading intensities in well-trained rowers.“

Conclusion:

“Although all loads elicited a sustained increase in forced capacity, only the 60% load elicited a sustained rise in mean arterial blood pressure, diastolic blood pressure, and systolic blood pressure, providing evidence for a metaboreflex response at this load.”

Read Acute cardiorespiratory responses to inspiratory pressure threshold loading >

Inspiratory Muscle Training Attenuates The Human Respiratory Muscle Metaboreflex

“Researchers of this study hypothesized that inspiratory muscle training (IMT) would attenuate the sympathetically mediated heart rate and mean arterial pressure increases normally observed during fatiguing inspiratory muscle work.”

Conclusion:

“Findings demonstrate that 5 weeks of resistive inspiratory muscle training is capable of increasing inspiratory muscle strength and attenuating the time-dependent rise in mediated heart rate and mean arterial pressure that occurs with resistive inspiratory work in healthy males.”

Read Inspiratory muscle training attenuates the human respiratory muscle metaboreflex >

Metabolic reflection of respiratory muscles limiting athletic performance

 

We’re grateful to our friends Fit & Breathe Concept for bringing this article to our attention. It’s written by Germain Fernandez Monterrubio, Bachelor of Science in Physical Activity and Sport and can be found in its original language here: ‘El reflejo metabólico de la musculatura respiratoria como factor limitante del rendimiento deportivo’.

We’ve translated the original text as best we can (as follows), but if it is not entirely clear then you may also be interested in reading this research, published in The Journal (2007) of The Physiological Society, ‘Insights into the role of the respiratory muscle metaboreflex’.

Metabolic reflection of the respiratory muscles as a limiting factor in athletic performance

Numerous studies show ventilatory fatigue (the inability of the respiratory muscles to achieve preural given pressure) (Chicharro, 2010) is considered as a limiting factor in performance, especially in disciplines that require endurance (such as marathon, rowing, swimming , triathlon etc).

One of the limiting factors that future studies will focus on is that of determining the specific influence of Metabolic Reflection of Respiratory Musculature (RMMR) in different cases.

The RMMR initiates fatigue of the respiratory muscles, which through III and IV afferents reach the supraspinal level, triggering a sympathetic response by vasoconstriction of peripheral muscle locomotive, which intensifies the fatigue of active muscles and increases also perception of effort, contributing to the limitation of return linked to intense aerobic exercise. (Romer and Polkey, 2008).

In aerobic performance, the TOTAL energy demand is not a limiting factor (Santalla, 2009), the production of energy in the time given is the determinant of fatigue… the “metaboreflex”. Respiratory muscles induce a number of mechanisms by which respiratory muscle fatigue can affect exercise tolerance (Jack mackerel, 2010, Santalla 2010, Romer and Polkey, 2008), incurring a series of cardiorespiratory interactions:

Pulmonary level:

  • Fatigue contraction of the diaphragm and accessory muscles of respiration.
  • Increased reflexes activated metabolites.
  • Increased afferent discharge (track III and IV).

Muscular level:

  • Increased efferent sympathetic discharge.
  • Increased vasoconstriction members.
  • Decreased oxygen transport.
  • Increased locomotor muscle fatigue.
  • Increased perception of effort.

In an experiment carried out with cyclists (Fischer, 2013) participants were induced to metaboreflex with post-exercise muscle ischemia, indicating that the increase in heart rate and the partial withdrawal of cardiac parasympathetic tone, is mainly attributed to increased cardiac sympathetic activity, and only after exercise with large muscle masses.

We speak of respiratory muscles (and mechanical); of autonomic nervous, central nervous system and cardiovascular system regulation in humans. A review by Douglas R. Seals raised the premise that if the RMMR represented the “Robin Hood” of the body to the locomotor muscles (Seals, 2001), determining that this reflex can have as its main objective the delivery of oxygen to the respiratory muscles, guarantees the ability to maintain pulmonary ventilation, adequate regulation of the gases in the blood flow and the pH and general organ homeostasis. The reflection is considered the “vital organ” responsible for supporting lung function and perfusion of the respiratory muscles, especially during physiological states in which there is competition for cardiac output, as in the exercise to maximum and submaximal intensities. This overrides the locomotor muscles.

Usually this phenomenon is found in those training for a sport or competition in which there will normally be a struggle between the respiratory muscles and the locomotor muscles for blood flow. Determining this is not so simple, as it also depends on the intervention of the central nervous system, which impinge on some physiological and psychological responses, such as the perception of effort. Generalizing, we can say that to focus on metabolic compromise reflects both muscles (respiratory and locomotor) at maximal or submaximal, rather than related to aerobic capacity.

Author: Germain Fernandez Monterrubio, Bachelor of Science in Physical Activity and Sport.

www.fermentourbano.com

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REFERENCES

  • SEALS, DR. (2001). Robin Hood for the Lungs? A respiratory metaboreflex that “steals” blood flow from locomotor muscles. J Physiol. 537(Pt 1):2
  • FISHER, JP y otros (2013). Muscle metaboreflex and autonomic regulation of heart rate in humans. J Physiol. 591.15 pp 3777–3788 3777
  • ROMER, LM y POLKEY, MI (2008). Excercise-induced respiratory muscle fatigue: implications for performance. J App Physiol. 104 pp 3879 3888
  • SANTALLA, A (2010). Presentation High Performance Program. Physiological Basis of Sports Performance. SE
  • CHICHARRO LOPEZ, JL (2010). Presentation Respiratory muscle fatigue induced by exercise: implications for clinical and performance.
  • HAJ GHANBARI, B. et alt. (2012) Effects of respiratory muscle training on performance in athletes: a systematic review with meta-analyses. J. of Strength & Conditioning Research.

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.

If you found this interesting (and if you found the translation not entirely easy to follow), you’ll probably find ‘Insights into the role of the respiratory muscle metaboreflex’ useful too.