Expiratory Muscle Strength Training (EMST) is a type of respiratory therapy that uses a handheld device to build the strength of muscles involved in exhalation. An EMST device is designed to provide resistance during forceful exhalation, which requires users to engage their expiratory muscles to overcome this resistance. 

By repeatedly using the device, individuals can increase the strength and endurance of their expiratory muscles, which is beneficial for improving cough strength, swallowing safety, speech production, and even some physical activities.

Key Components and Mechanism of the EMST Tool

1. Device Structure: The EMST tool typically has a mouthpiece that the user exhales into, along with a resistance adjustment dial or valve. The dial controls how much resistance the device provides, allowing the user to adjust the difficulty based on their current strength level.

2. Adjustable Resistance: The resistance dial allows users to gradually increase the difficulty level as their muscle strength improves. When a user exhales through the device, the resistance creates a threshold pressure that their expiratory muscles must exceed to force the air out. This resistance can be increased or decreased to provide a progressive training effect, similar to increasing weights in strength training.

3. Training Regimen: A common training protocol involves exhaling forcefully through the device multiple times per session, usually for a few sessions each day over several weeks. Talk with your clinician to get an individualized home exercise plan that works for you. Typically, users start with a lower resistance setting and gradually increase it as their muscles become stronger. Consistent training can lead to noticeable improvements in expiratory muscle performance and endurance.

Benefits of EMST

EMST is particularly useful in clinical settings for populations who need to improve muscle strength for respiratory, swallowing, and vocal functions:

• Improved Cough Function: EMST helps strengthen the muscles required for a strong, productive cough. A strong cough is essential for clearing the airways and protecting against aspiration (inhalation of food or liquid into the lungs), which is especially important for individuals with neurological conditions or respiratory muscle weakness.

• Swallowing and Airway Protection: For individuals with dysphagia (difficulty swallowing), such as those with Parkinson’s disease or stroke, EMST can improve the coordination and strength of muscles involved in swallowing. Studies show that EMST can reduce the risk of aspiration by enhancing the strength of the expiratory muscles that help clear the throat and airways during swallowing.

• Speech and Voice Quality: EMST can be beneficial for voice and speech production, particularly for individuals with conditions that affect vocal control, like Parkinson’s disease. Expiratory muscle strength training can enhance breath support, leading to clearer, louder, and more controlled speech.

• Athletic and Vocal Performance: Some athletes and professional vocalists use EMST to improve their respiratory muscle endurance, which can help with activities requiring sustained breath control, such as swimming, singing or endurance running.

Clinical Applications of EMST

EMST has been studied in a variety of clinical populations and has shown promising results for different conditions:

• Parkinson’s Disease: Parkinson’s disease can weaken respiratory muscles, leading to poor cough and increased aspiration risk. EMST has been shown to help these patients improve their cough force and swallowing ability.

• Stroke Rehabilitation: Post-stroke patients often experience weakened respiratory muscles, affecting both breathing and swallowing. Studies show that EMST can aid in the recovery of these functions, improving both quality of life and health outcomes.

• Multiple Sclerosis (MS): MS patients may experience muscle weakness, including in the respiratory muscles. EMST helps build muscle strength and supports better respiratory health, aiding in airway protection and voice volume control.

Scientific Evidence Supporting EMST

Research has shown that EMST can be effective for improving respiratory muscle strength and related functions. These references can provide further reading on EMST and its applications in various health conditions, supporting the evidence for its clinical and functional benefits.

Here are a few key studies:

• Sapienza, C., & Troche, M. (2012). “Respiratory muscle strength training: theory and practice”. Plural Publishing.

o This book covers the theoretical and practical aspects of respiratory muscle strength training, including EMST. It describes the benefits of respiratory muscle training for various clinical populations, particularly in preventing aspiration and improving quality of life.

• Pitts, T., Bolser, D., Rosenbek, J., Troche, M., & Sapienza, C. (2009). “Impact of expiratory muscle strength training on voluntary cough and swallow function in Parkinson disease”. Chest, 135(5), 1301-1308.

o This study demonstrated that EMST improved cough strength and swallow safety in patients with Parkinson’s disease, reducing their risk of aspiration-related complications.

• Kim, M., & Sapienza, C. (2005). “Implications of expiratory muscle strength training for rehabilitation of the elderly: tutorial”. Journal of Rehabilitation Research & Development, 42(2), 211-224.

o This article reviews the potential benefits of EMST for elderly populations, including improvements in swallowing function, cough strength, and voice volume, which can help reduce health risks and improve quality of life.

• Smither, A., & Gillivan-Murphy, P. (2015). “Expiratory muscle strength training in adults with multiple sclerosis”. Journal of Clinical Neurology, 11(1), 27-34.

o This study showed that adults with multiple sclerosis experienced improvements in respiratory muscle strength and breathing function after participating in an EMST program.

Summary

The EMST tool is a valuable therapeutic device used to strengthen expiratory muscles, with applications in respiratory health, swallowing, and speech therapy. By providing adjustable resistance, EMST allows users to progressively increase their muscle strength, which is particularly beneficial for individuals with neurological conditions, respiratory muscle weakness, or those who simply want to improve their respiratory health.

Disclaimer: This content is for educational purposes only and is not medical advice. It does not replace evaluation or treatment by a licensed SLP or physician in your state or country. Always consult a qualified provider before starting any therapy.