Lingual Strengthening: History & Rationale

By Amanda Warren, MS, CCC-SLP (guest blogger) and Karen Sheffler, MS, CCC-SLP, BCS-S of SwallowStudy.com

Is lingual strengthening (aka, tongue strengthening) in your exercise program? Exercises should be targeted to your specific problems with swallowing. Your therapist can give you the rationale of if and why tongue strengthening is necessary for you. Make sure to follow a customized exercise program prescribed by your healthcare providers. Don’t just go pulling up turnips!

Mouth stretches, wagging the tongue back and forth, posterior consonants (like “ga”), blowing bubbles or blowing up a balloon… For decades, our field of swallowing therapy was full of well-meaning clinicians throwing all the tools in their toolboxes at patients to hope to improve their swallow function. This focus on oral-motor therapy lead industry to sell so many tools. Recently, speech-language pathologists (SLPs), who are implementing Evidence-Based Practice (EBP), have been questioning some of these outdated exercises. Unfortunately, the research has still been lacking on whether many of these non-swallowing oral exercises actually improve swallowing. Therapists are also now looking for exercises and tools specifically targeted to what is actually wrong with the person’s swallow (based on instrumental examinations of swallowing physiology). The clinician must analyze the instrumental swallowing evaluations to pinpoint what parts of the swallow are abnormal or impaired.

When the tongue and tongue base are impaired, the clinician may see issues such as:

• poor bolus control;
• reduced tongue strength, movement and coordination, leaving residue all around the mouth;
• decreased lingual stripping, leaving residue especially on the tongue and hard palate;
• decreased tongue base to posterior pharyngeal wall contact,
• reduced tongue base propulsion causing decreased epiglottic deflection, and
• significant pharyngeal residue, to name a few!

Therefore, one area of oral-motor therapy that has been of particular clinical interest for its potential to impact swallowing safety and efficiency has been lingual strengthening. This article will review what has research shown us over the years about tongue/lingual strengthening.

Can SLPs Actually Impact Safety & Efficiency of the Swallow with Lingual Strengthening?

There’s a good body of literature which suggests that isometric exercise and training with maximum isometric pressures can have a positive impact on:

• Overall tongue strength and
• Functional swallowing outcomes (e.g., eating more regular foods and liquids without foods getting stuck, which is improving the efficiency of the swallow, and without foods and liquids going down the wrong way, which is the safety of the swallow).

First some definitions and background:

Isometric exercises might also be called static strength training or muscle contraction without movement.  It’s what you’re doing when you ask your client to hold a specific position for a period of time.

Maximum isometric pressure is a measure of the most strength a person can put into the task, such as pushing as hard as you can.

BACKGROUND NOTE: In the early 2000s, the Iowa Oral Performance Instrument (IOPI) came on the market.  This lip and lingual strengthening device has an air filled bulb attached to an electronic device which gives a numeric measurement of pressure in kilopascals. It displays a number of how hard or accurate the client is pushing with the tongue or lips. For examples, you can obtain the maximum pressure generated against the bulb, as well as check the endurance of maintaining a specific targeted pressure against the bulb over time.  And since its creation, clinicians and researchers alike have been using the IOPI and other biofeedback devices to provide information to patients during their isometric oral exercises.

Targeted Therapy for Lingual Strengthening

What specific targets do we hope to improve when we work on the tongue? How do we achieve a safer and more efficient swallow?

While we review the research on lingual strengthening in the following targeted areas, it is important to keep in mind that these cannot be necessarily considered isolated events. The swallow is complex and one aspect is very dependent on another in a beautiful synchronistic event.

Tongue exercises hope to improve:

1. Tongue pressures to increase the driving force of the tongue during the swallow,
2. Tongue bulk,
3. Bolus control, and
4. Clearance of the bolus through the mouth and throat during the swallow.

Let’s take a look at some literature behind each of these areas.

1. Improve tongue pressures to improve the driving force of the tongue on the ball (bolus) of food/liquid in the mouth.

In a 2005 research study titled: “The Effects of Lingual Exercise on Swallowing in Older Adults” [PubMed], Robbins and colleagues introduced the idea that healthy older adults who underwent an 8-week progressive lingual resistance exercise program “successfully and significantly” increased their lingual isometric strength.  They demonstrated carryover of these isometric exercises, as the healthy adults also had higher swallowing pressures, despite the fact that the protocol did not include a swallowing task.

Robbins and colleagues repeated a similar study in 2007 with 10 patients with ischemic strokes (6 acute, or less than 3 months out; 4 chronic, or more than 3 months out).  In the same fashion as the 2005 study, the protocol included isometric exercises only, not dynamic swallowing exercises. The paper, titled: “The Effects of Lingual Exercise in Stroke Patients with Dysphagia” [PubMed], revealed their successes. These patients increased isometric lingual pressure generation and had greater lingual strength during swallowing.  There were other added benefits as well, which will be addressed in subsequent sections.

More recently in 2014 [PubMed], Rogus-Pulia and colleagues (including Dr. Robbins) expanded on that early data with the Swallow Strengthening Oropharyngeal (Swallow STRONG) Program with a device that facilitated isometric progressive resistance oropharyngeal (I-PRO) therapy. The SwallowSTRONG device was a more complex device with multiple palatal sensors, rather than the isolated IOPI bulb, but it is no longer on the market. The study followed 56 veterans with diverse medical diagnoses, but all with dysphagia, for an 8-week training program. They demonstrated improvements in lingual pressures in both the anterior and posterior portions of the tongue.  These veterans also demonstrated improvements in quality of life scores and were able to eat less-restrictive (more regular) diets.

In 2003, Lazarus and colleagues, in their article called: “Effects of Two Types of Tongue Strengthening Exercise in Young Normals” [PubMed], compared the following three groups of healthy subjects (ages 20-29 years):

1. Control group: Receiving no treatment,
2. Treatment group: Receiving ‘standard’ tongue strengthening exercises with a tongue depressor, and
3. Treatment group: Receiving tongue strengthening exercises with the IOPI, thus providing biofeedback about whether or not they were performing the exercise with sufficient effort.  

One might hypothesize that this third group, the one with biofeedback, would make the most striking improvements. However, in reality, while both treatment groups made improvements greater than the control group (with no exercise), their improvements were not statistically different than one another. That is, the cheaper option of pushing against a tongue depressor, without biofeedback, was just as effective as the more expensive device with digital biofeedback. It should be emphasized that this was a study with young healthy normal subjects. More research is clearly needed comparing devices with numeric biofeedback versus less expensive tools for lingual strengthening that can be taken home by our clients who have dysphagia.

The Dysphagia Grand Rounds Episode 5 (2017, May) covered the research by Steele and colleagues from 2016 and earlier (see references below and [PubMed]). Dr Catriona Steele, PhD, CCC-SLP, F-ASHA (from the Swallowing Rehabilitation Research Laboratory at the Toronto Rehabilitation Institute) described how the initial tongue movement of swallowing is upward and forward to the alveolar ridge. She gave the analogy of how we push off with our legs from the edge of a swimming pool. The more we bunch up our legs and spring off with force, the farther we go. The tongue may drive the bolus through the pharynx better with increased strength of this initial push off from the alveolar ridge. Steele stated:

“The harder the tongue compresses against that wall as it is getting ready to initiate the swallow, the better the drive is going to be when it releases.”

2. Increase tongue bulk through strengthening exercises.

In the two Robbins articles referenced above, in addition to the improvements in tongue pressures, the authors point out increased tongue bulk as well.  In the Robbins 2005 article studying healthy elders, of the subset of participants who underwent MRI as a pre/post-treatment measure, all showed increase in lingual volume and muscle mass. Similarly, in the 2007 article about patients after stroke, 2 of 3 who underwent MRI showed increase in lingual volume as well.

Similar results were found in a case study by Juan and colleagues in 2013 [PubMed].  A 56 year old woman who had a stroke underwent 8-weeks of I-PRO therapy, using a device similar to the 2014 Rogus-Pulia article above. At the end of her therapy, she demonstrated increased isometric tongue pressures and increased swallowing pressures, but she also demonstrated an 8.37% increase in lingual volume when intrinsic and extrinsic tongue muscles were measures on MRI.

3. Improve bolus control to potentially reduce risk for aspiration.  The idea being that lingual strengthening (and skill-training/accuracy exercises) may have a positive impact on oral bolus control which may in turn improve bolus containment and prevent the loss of the bolus to the airway before the swallow.

Reduced tongue strength has been identified as a risk factor for aspiration. In 2010, Butler and colleagues studied a group of 73 healthy older adults, testing isometric tongue strength, swallowing tongue strength, and handgrip strength. When fully evaluating their swallowing and rating with the Penetration-Aspiration Scale (PAS), researchers discovered that 38% of the healthy community dwelling older adults were aspirators.  The group of people who aspirated had significantly less isometric tongue strength and swallowing tongue strength when compared to the non-aspirators.  In addition, Steele and Cichero (2014) identify poor tongue driving force as one factor associated with aspiration in their systematic review of physiological factors related to aspiration risk [PubMed].  

So it’s not surprising to find that targeting isometric tongue pressures would result in improvements in tongue strength that might also result in decreased penetration and aspiration or improved safety of the swallow.  For example, in the already cited Robbins 2007 research above, they showed reduced penetration and aspiration (PAS scores) over the course of the 8-week treatment protocol targeting tongue strengthening. In fact, a greater number of patients were able to finish the entire videofluoroscopic oropharyngeal swallow study protocol because of their reduced frequency of aspiration.

In the early 2000s, several researchers pointed out that swallowing was a sub-maximal pressure task, meaning we do not use our maximum isometric pressures (MIP) to swallow.  Researchers found that our maximum tongue pressures reduce with aging, but our tongue’s sub-maximal swallowing pressures do not decrease significantly with age (Nicosia et al 2000, Youmans et al 2009).  As such, in 2013 [PubMed], Steele and colleagues altered Robbins’ protocol to target both maximum strength (strength targets at >80% of max) and accuracy (targets in the range of 20-90% of MIP) using the IOPI bulb.  Outcomes included not only improvements in tongue strength, but also a reduction in penetration and aspiration for the majority of the participants. The authors do note that the reason Penetration and Aspiration Scale (PAS) scores improved is not clear and may have been associated with spontaneous recovery over time in this small group of neurologically impaired patients with dysphagia.  

4. Improve tongue strength to more efficiently clear the bolus through the mouth and throat with less residue left behind. This can also reduce aspiration risk after the swallow.

It is important to keep in mind that the oral and pharyngeal phases of the swallow do not stand in isolation from one another.  Changes in one often have an impact on the other. In that way, improved tongue strength may also have a positive impact on both oral and pharyngeal clearance with decreased residue in the throat after the swallow, impacting swallow efficiency.

In the Robbins 2007 above, participants who had a stroke had reduced oropharyngeal residue after using the IOPI protocol (in addition to the other benefits already described).  In the Juan 2013 case study, one improvement noted after tongue strengthening with the I-PRO was reduced pharyngeal wall residue.

However, in the Steele 2013 study noted above, they did not find improved clearance and reduced residue in the valleculae and pyriforms, and in fact the residue worsened in some people. Therefore, in 2016, Steele and colleagues expanded their previous work into a larger, randomized controlled trial with 14 participants.  In this more detailed work, one group performed training similar to the 2013 study (strength targets and accuracy targets) and the other group did a skill-based task of posterior tongue pressure with a gradual release of pressure plus an effortful swallow with a slow release of pressure. They found improvements in tongue strength in both groups, but they also found decreased residue in the valleculae in both groups. They noted that they also had an improved method to measure residue which other studies did not use (Normalized Residue Ratio Scale). The finding of reduced residue after the swallow is hopeful for a reduction in risk for aspiration after the swallow on that residue.

In 2015, Lenius and colleagues lead a study called: “Effects of Lingual Effort on Swallow Pressures Following Radiation Treatment.” [PubMed] Twenty participants with head and neck cancer who had undergone radiation therapy (with and without chemotherapy) were assessed via videofluoroscopic swallow studies performing their typical swallows and cued swallows to specifically increase the lingual force during the swallow.  This study did not include a course of lingual exercises, but biofeedback via the IOPI was used during the assessment for the clinician to ensure there was an actual difference between the two swallows. The effortful lingual swallows significantly increased base of tongue pressures in 19 out of the 20 participants.  One might hypothesize that the improvements seen in base of tongue pressures would have a positive impact on pharyngeal residue and efficiency of the swallow, though this was not directly assessed as a part of the 2015 study. The authors did speculate that the effortful lingual swallow would also increase the action by the upper pharyngeal constrictors for improved tongue to pharyngeal wall contact, as the glossopharyngeus muscle originates at the sides of the tongue.

Subsequently in 2017, Kim and colleagues worked with 35 people who were status post stroke [PubMed] with documented dysphagia on videofluoroscopic swallow studies (VFSS). These participants had reduced tongue muscle strength (<10 kPa MIP).  Participants engaged in a 4-week course of intensive training including tongue-to-palate resistance training (TPRT) without any device at all.  Afterwards, subjects in the experimental group had statistically significantly larger gains in tongue strength, measuring anterior and posterior tongue pressures, than controls. The experimental group also made more pronounced improvements in their oral and pharyngeal VFSS scores. Unfortunately, the authors did not specify which of the following pharyngeal phase components improved: pharyngeal triggering, vallecular residue, pyriform sinus residue, laryngeal elevation, epiglottic closure, pharyngeal wall coating, pharyngeal transit time and aspiration. Therefore, this list shows that they tested and scored “residue” but did not specifically report on it. However, during the discussion section, they speculated that increased lingual pressures would have a positive effect on clearing the bolus through the pharynx and reducing residue. This study serves as a nice follow up to the 2015 Lenius article described above, as it shows that the tongue can be strengthened through isometric resistance exercises both with and without device facilitation.  However, in our anecdotal experience, device-assisted therapies tend to have higher compliance, as patients are motivated by the presence of the device.

Summary

Dr Catriona Steele discussed tongue strengthening literature on Episode 5 (May, 2017) of the Dysphagia Grand Rounds and stated:

“I am very confident that we can improve tongue strength,” and she noted “This is consistent finding in the literature.”

Steele noted that she has not seen any maladaptive side-effects yet when ramping up the intensity of lingual strengthening exercises. However, she has been also studying lingual skill and accuracy training, which reminds us to ask ourselves: How do we know that the tongue is only weak? Further consideration is needed into the benefits of not only strengthening, but also exercise targeting accuracy and skill training. We know that our therapy tool box should have more than a one-size-fits-all lingual strengthening program. Clinicians customize therapy according to the pathophysiology noted on the individual’s instrumental examination, meaning we target the therapy of strengthening and/or accuracy-based exercises to what is “wrong” with the swallow.

It is clear that more research needs to be done. It is promising that a significant portion of the lingual literature points us toward targeting maximum isometric pressures (MIPs), especially when the deficits related to the tongue have been found to be a major issue in our individual patient with dysphagia.  While some evidence conflicts, there’s data suggesting that improving tongue strength in isolation/non-nutritive tasks may do the following:

• have a positive benefit on swallow strength in nutritive swallowing,
• improve tongue bulk (combating sarcopenia – or muscle mass loss with aging), and
• improve both safety aspects of swallowing (reduced aspiration) as well as efficiency aspects (reduced oral and pharyngeal residue).

********

Financial Disclosures:

Amanda Warren and Karen Sheffler received a small stipend for writing this article from the company: ABILEX™ Oral Motor Exerciser. SEE APPENDIX below for more information written by us for individuals with dysphagia and for the SLPs performing dysphagia evaluations and dysphagia treatment.

********

APPENDIX: 

UNFORTUNATELY, TRUDELL MEDICAL HAS DISCONTINUED PRODUCTION OF ABILEX

Information still shared about the device:

Here is more information on lingual strengthening and an exercise program with the ABILEX™ Oral Motor Exerciser, from Trudell Medical International. This was written for people with dysphagia and for speech-language pathologists who treat them.

Please see my Product Review page to read more about a person’s success story after using the Abilex device.

FOR PEOPLE WITH SWALLOWING PROBLEMS:

A Speech-Language Pathologist will assess your swallow function and make a tailored therapy plan just for you. He or she will typically increase the intensity and frequency of your exercise regimen over several weeks, which may include multiple sets of exercises to perform at least 5 times a week or every day for up to 8 weeks or more. It is important to start swallowing therapy, like tongue exercises, as early as you can. You can begin while you are still in the hospital or rehabilitation center, as long as that is okay per the advice of your medical team and swallowing specialist. (Note: sometimes after specific procedures and surgeries, it is important to wait).

If tongue exercises are in your therapy plan, then having a hand-held device like the ABILEX™ may give you more motivation to complete your exercise program. It is important to reliably perform exercises at the prescribed frequency and intensity to get the best results. The Abilex is a convenient tongue exerciser with a broad and soft bulb that you can push against for isometric resistance. (You can also do coordination and range of motion exercises with the tongue and strengthening exercises with the lips with this device.)  The Abilex’s larger bulb and overall design make it easier and more comfortable to press against than the small IOPI bulbs (mentioned above). There is a small indentation in the middle of the Abilex bulb, and people find that their tongues do not slip off, as they do with the IOPI bulb. The larger bulb of the Abilex is good for irregular and high palates too. The Abilex is very inexpensive and easily washable, rather than the more expensive IOPI device with disposable bulbs.

Additionally, the IOPI device can still be used at your swallowing clinic to establish your baseline pressure measurements (of tongue or even lip pressure). You can practice on your own with your Abilex device. Then, during each therapy session, your swallowing specialist can use the IOPI to help quantify your improvements in tongue strength. This process keeps exercise easy and affordable at home or on your own, but then also motivating to see your actual numeric improvements and to set new targets on the IOPI.  

FOR SPEECH-LANGUAGE PATHOLOGISTS:

As a part of swallowing therapy, lingual strengthening can be initiated even at the acute care level.  A good therapy plan always begins with an instrumental assessment of swallow function to create a tailored rehabilitation plan unique for each patient. The intensity and frequency of the exercises you recommend should increase gradually as tolerated by your patient. The principles of neuroplasticity are at work. It is about more than just use-it-or-loose it, it is also about making sure the exercises are salient to the patient and done at sufficient intensity and frequency to create change.

The IOPI described above can be used to establish a baseline and set improvement targets. Many patients find this quite motivating. When your patient is physically and cognitively able, you can recommend lingual strengthening exercises outside of swallowing therapy sessions. You can also train family and/or caregivers to remind, assist and cue the exercises. This can start in the hospital and continue as they transition to rehabilitation, a skilled nursing facility, and home. Patient-directed exercises have been historically only done unaided or with a tongue depressor. However, device-driven exercises may allow for better patient adherence to the exercise program.

The ABILEX™ Oral Motor Exerciser is a hand-held and light-weight tool with a broad, soft, air-filled bulb that patients can push against for isometric resistance for lip and lingual strengthening. The larger bulb and overall design make it easier than the disposable IOPI bulbs. Patients with a high palate or a torus palatinus (normal bony growth on the hard palate in about 20-30% of the population) have trouble using the small IOPI bulb. Many patients find that their tongue slips off the IOPI bulb, whereas patients find the indentation in the Abilex bulb an easy and comfortable target, even when their tongues and mouths are sore. We find that when asking patients to do these daily exercises on their own, a dedicated tool helps them keep up with exercises at the optimal frequency and intensity.

REFERENCES:

Juan, J., Hind, J., Jones, C., McCulloch, T., Gangnon, R. & Robbins, J. (2013). Case study: Application of isometric progressive resistance oropharyngeal therapy using the Madison Oral Strengthening Therapeutic device. Topics in Stroke Rehabilitation, 20(5), 450-70. doi: 10.1310/tsr2005-450.

Kim, H.D., Choi, J.B., Yoo, S.J., Chang, M.Y., Lee, S.W. & Park, J.S. (2017). Tongue-to-palate resistance training improves tongue strength and oropharyngeal swallowing function in subacute stroke survivors with dysphagia. Journal of Oral Rehabilitation, 44(1), 59-64. doi: 10.1111/joor.12461.

Lenius, K., Stierwalt, J., LaPointe, L.L., Bourgeois, M., Carnaby, G. & Crary, M. (2015). Effects of lingual effort on swallow pressures following radiation treatment. Journal of Speech Language and Hearing Research, 58(3), 687-97. doi: 10.1044/2015_JSLHR-S-14-0210.

Lazarus, C., Logemann, J.A., Huang, C.F. & Rademaker, A.W. (2003). Effects of two types of tongue strengthening exercises in young normals. Folia Phoniatrica et Logopaedica, 55(4), 199-205.

Nicosia, M. A., Hind, J. A., Roecker, E. B., Carnes, M., Doyle, J., Dengel, G. A., & Robbins, J. (2000). Age effects on the temporal evolution of isometric and swallowing pressure. Journals of Gerontology: Series A: Biological Sciences and Medical Sciences, 55, M634–M640. doi:10.1093/gerona/55.11.M634

Rogus-Pulia, N., Rusche, N., Hind, J.A., Zielinski, J., Gangnon, R., Safdar, N. & Robbins, J. (2016). Effects of device-facilitated isometric progressive resistance oropharyngeal therapy on swallowing and health-related outcomes in older adults with dysphagia. Journal of the American Geriatrics Society, 64(2), 417-24. doi: 10.1111/jgs.13933.

Robbins, J., Levine, R., Wood, J., Roecker, E.B., Luschei, E. (1995). Age effects on lingual pressure generation as a risk factor for dysphagia. Journal of Gerontology: Series A: Biological Sciences and Medical Sciences, 50, M257–M262. doi: 10.1093/gerona/50A.5.M257.

Robbins, J., Gangnon, R.E., Theis, S.M., Kays, S.A., Hewitt, A.L. & Hind, J.A. (2005). The effects of lingual exercise on swallowing in older adults. Journal of the American Geriatrics Society, 53(9), 1483-9.

Robbins, J., Gangon, R.E., Theis, S.M., Kays, S.A., Hewitt, A.L., Hind, J.A. (2007). The effects of lingual exercise in stroke patients with dysphagia. Archives of Physical Medicine and Rehabilitation, 88(2), 150-158. DOI: 10.1111/j.1532-5415.2005.53467.x

Steele, C. M., Bailey, G. L., Polacco, R. E. C., Hori, S. F., Molfenter, S. M., Oshalla, M., & Yeates, E. M. (2013). Outcomes of tongue-pressure strength and accuracy training for dysphagia following acquired brain injury. International Journal of Speech-Language Pathology, 15(5), 492–502. https://doi.org/10.3109/17549507.2012.752864

Steele, C., Molfenter, S., Péladeau-Pigeon, M., Polacco, R. and Yee, C. (2014). Variations in tongue-palate swallowing pressures when swallowing xanthan gum-thickened liquid. Dysphagia, 29, 1-7.

Steele, C.M., et al. (2016). A randomized trial comparing two tongue-pressure resistance training protocols for post-stroke dysphagia. Dysphagia, 31(3), 452–461. doi:  10.1007/s00455-016-9699-5

Steele, C.M. & Cichero, J.A. (2014). Physiological factors related to aspiration risk: A systematic review. Dysphagia, 29(3), 295-304. doi: 10.1007/s00455-014-9516-y. Epub 2014 Feb 23.

Youmans, S.R., Youmans, G.L., Stierwalt, J.A. (2009). Differences in tongue strength across age and gender: is there a diminished strength reserve? Dysphagia, 24(1), 57-65. doi: 10.1007/s00455-008-9171-2.

Thank you to my guest blogger and co-writer for the collaboration:

Amanda Warren, MS, CCC-SLP, is a medical Speech-Language Pathologist practicing in the city of Boston, MA. She has extensive experience in outpatient, acute care, rehabilitative care, skilled nursing and home care environments. Amanda teaches Speech-Language Pathology at the undergraduate level at Gordon College and at the graduate level at Boston University, Bridgewater State, and Emerson College. She is an author of continuing education courses at Northern Speech Services. She has a special interest in clinical instruction, palliative dysphagia management, augmentative communication at the end of life, and patient-family advocacy and education.