the tongue plays a major role in swallowing and is essential to ensure normal swallowing 
 function .
the primary functions of the tongue include food mastication , bolus formation , 
 manipulation , and propulsion into the pharynx1 .
moreover , it also contributes to respiration and speech 
 functions2 . during the oral stage of 
 swallowing , the tongue squeezes food against the hard palate of the mouth , and moves the 
 bolus from the anterior to the posterior region of the tongue for propulsion into the 
 pharynx3 .
neurogenic disorders , such as 
 a stroke or parkinson s disease , can lead to deficits in the sensory and motor functions of 
 the tongue .
this can further lead to dysphagia in both the oral and pharyngeal stages of 
 swallowing , such as difficulties with the mastication and manipulation of food , vallecular 
 and pharyngeal residues , and aspiration4 , 5 .
therefore , sufficient tongue muscle 
 strength is a determining factor for safe swallowing . pushing
the tongue against the hard palate or against an external resistance , such as a 
 tongue depressor , has been described as a basic strengthening exercise for the tongue6 . however , in this basic approach for 
 strength training of the tongue , the level of resistance and the volume of training 
 stimulus  parameters necessary to optimize strength outcomes  are not systematically 
 controlled . the iowa oral performance instrument ( iopi medical llc , redmond , wa ) is a standardized 
 portable device that can be used to quantify tongue muscle strength , thus allowing the 
 clinician to set the level of resistance necessary to achieve optimal gains in strength , and 
 also providing visual feedback of performance to the patients to guide training7 . in the present study
, we aimed to evaluate 
 the effectiveness of a resistance training program for the tongue in order to improve 
 swallowing function in stroke patients with dysphagia .
fifty stroke patients with dysphagia were eligible for this study , which was conducted from 
 april 2015 to july 2015 .
the inclusion criteria for participation were as follows : 1 ) 
 dysphagia from a stroke that was confirmed by a videofluoroscopic swallowing study ( vfss ) , 
 2 ) onset duration > 6 months , 3 ) mini - mental state examination ( mmse ) 
 score  24 .
the exclusion criteria were as follows : 1 ) previous stroke ; 2 ) severe orofacial 
 pain including trigeminal neuropathy ; 3 ) significant malocclusion or facial asymmetry ; 4 ) 
 severe communication disorder , such as severe aphasia .
all participants provided written 
 informed consent , and the study protocol was approved by the institution review board .
this study was designed as a 6-week , single - blind , randomized controlled study .
each 
 eligible participant was randomly allocated to the experimental training or control group 
 using opaque envelopes that contained codes specifying his or her group membership .
both 
 groups received traditional dysphagia therapy for 30  min per day , and the experimental group 
 additionally received strength training for the tongue using the iopi .
when we measured 
 the pressure of the anterior tongue region , the bulb was positioned on the hard palate 
 immediately behind the upper gingiva and touched the anterior 10  mm of the tongue dorsum . 

the subjects were instructed to press the bulb toward the hard palate with the tongue as 
 hard as possible for 2 s. for the posterior tongue region , the bulb was placed on the 
 anterior aspect of the posterior hard palate and the subjects were instructed to press the 
 bulb in the same manner as described above .
please press the bulb as hard as possible for 2 s. next , i will move 
 it backwards a little further .
the 1-repeated maximum contraction ( i.e. , 1 
 rm ) for anterior and posterior elevation of the tongue was measured using the iopi .
the 
 training protocol of the experimental group was similar to that for the measurement of 
 tongue strength , and resistance was set at the 80% level of maximal isometric tongue 
 pressure .
training was performed for 6 weeks at a frequency of 5 times per week and an 
 intensity of 5 sets of 10 trials per day , amounting to a total daily volume of 50 
 repetitions each for the anterior and posterior regions of the tongue .
a minimum rest period 
 of 30  s was provided between sets , with longer durations considered to accommodate patients 
 fatigue .
trials in which the target training level was not reached were repeated to 
 standardize the volume of resistance training .
the effectiveness of the training was evaluated by comparing pre- and post - training 
 measures .
the iopi was used to determine baseline 1 rms of the anterior and posterior 
 regions of the tongue for patients in both the experimental and control groups .
the 1 rms 
 were re - evaluated at the end of the 6-week training program .
swallowing function was also 
 evaluated at baseline and following the 6-week training intervention using the 
 videofluoroscopic dysphagia scale ( vds ) based on videofluoroscopic swallowing study ( vfss ) . 

the vds consists of 14 items , which can largely be categorized into 
 an oral phase ( 7 items : lip closure , bolus formation , mastication , apraxia , tongue to palate 
 contact premature bolus loss , and oral transit time ) and a pharyngeal phase ( 7 items : 
 pharyngeal triggering , vallecular residues , pyriform sinus resides , laryngeal elevation , 
 pharyngeal wall coating , pharyngeal transit time , and aspiration ) .
the score ranges from 0 
 to 100 , and a higher score indicates a higher severity of dysphasia9 .
participant characteristics were analyzed using a statistical software program ( spss 
 statistics 20 , ibm , armonk , ny ) , and descriptive statistics are presented as mean  standard 
 deviation . the shapiro - wilk test was used to check the normality of the outcome variables . 
 to evaluate the effects of training , paired t - test
independent t - test was used to compare the changes in 
 outcome measures between the two groups .
there were no significant differences between the baseline characteristics in the two 
 groups ( table 1table 1.characteristics of participantscharacteristicsexperimental group ( n=15)control group ( n=14)age ( years ) meansd ( range)67.310.6 ( 5182)65.811.5 ( 5280)gender , male / female6/97/7etiologyhemorrhage86infarction78time since onset of stroke , weeks , mean  sd ( range)25.377.43 ( 1945)26.386.81 ( 1743)sd : standard deviation ) .
the experimental group showed significant improvements from 18.93  6.75 to 
 20.73  6.61 for the anterior region , and from 16.2  4.69 to 18.47  4.09 for the posterior 
 region . on the other hand ,
the control group showed improvements from 22  5.74 to 22.86  
 5.36 for the anterior region , and from 17.29  4.3 to 17.71  4.36 for the posterior region . 

however , the change in the control group was only statistically significant for the anterior 
 region .
no statistically significant difference in either the anterior or the posterior 
 region scores was observed between the two groups after the intervention ( table 2table 2.comparison of results between experimental group and control groupregionexperimental groupcontrol groupbefore treatmentafter 4-week treatmentbefore treatmentafter 4-week treatmentanterior region18.93  6.7520.73  6.6122  5.7422.86  5.36posterior region16.2  4.6918.47  4.0917.29  4.317.71  4.36the values are mean  standard deviation . unit : pressure*p<0.05 , * * p<0.01 by paired t test between initial and final scores in the 
 group ) .
sd : standard deviation the values are mean  standard deviation . unit : pressure * p<0.05 , * * p<0.01 by paired t test between initial and final scores in the 
 group regarding the vds evaluation based on vfss , the experimental group showed statistically 
 significant differences in both the oral and pharyngeal stages , as well as in the total 
 score . on the other hand ,
the control group showed significant improvements in the vds score 
 for the oral stage of swallowing and in the total score .
no statistically significant 
 difference in vds scores was observed between the two groups after the intervention ( table 3table 3.comparison of results between experimental group and control groupitemsexperimental groupcontrol groupbefore treatmentafter 4-week treatmentbefore treatmentafter 4-week treatmentoral phase16.274.7214.674.4516.824.1116.644.13pharyngeal phase42.876.8540.776.1241.756.841.56.84total score59.1310.7455.439.3558.579.7558.149.83the values are mean  standard deviation.*p<0.05 , * * p<0.01 by paired t test between initial and final scores in the 
 group ) .
* p<0.05 , * * p<0.01 by paired t test between initial and final scores in the 
 group
consequently , it has been considered as a remedial approach for improving 
 swallowing functions . in this study
, we aimed to confirm the effects of tongue resistance 
 training on tongue muscle strength and overall swallowing function .
our 6-week protocol involved a training resistance of 80% 1 rm and a volume of 50 
 repetitions each for the anterior and posterior regions of the tongue .
the protocol yielded 
 significant gains in strength in the anterior and posterior regions of the tongue , and 
 improved function in both the oral and pharyngeal stages of swallowing .
in general , the 
 functional recovery of skeletal muscle increases rapidly within the first 6 months after a 
 stroke10 . a training intensity of 
 6080% 1 rm has been shown to be effective in improving the strength of skeletal 
 muscles11 .
a very low resistance 
 intensity will not provide sufficient loading of the muscle to stimulate increases in 
 strength , whereas a very high resistance intensity will lead to fatigue and an inability to 
 complete the volume of repetitions that is necessary to optimize strength gains .
robbins et 
 al.4 reported increases in tongue 
 strength and volume / area in stroke patients following an 8-week resistance training program 
 for the tongue , involving a training resistance between 60% and 80% 1 rm .
based on these 
 results , we assumed that a training stimulus of 80% 1 rm would be adequate when designing 
 the present study .
the effectiveness of the resistance - training program in improving the oral and pharyngeal 
 stages of swallowing is an important and novel finding of our study . in the oral stage of 
 swallowing ,
further , tongue strength and function are essential to squeeze food against the 
 hard palate , both for movement of the bolus from the anterior to the posterior regions of 
 the tongue and for propulsion into the pharynx .
tongue strength is also important for 
 creating a sufficiently high pressure within the oral cavity , to reduce the oral and 
 pharyngeal transit time , vallecular residues , and risk of aspiration as a result of improved 
 airway protection .
steele et al.12 also 
 suggested that tongue resistance training is an effective method for reducing aspiration and 
 penetration .
thus , increased tongue strength has a positive effect on the swallowing - related 
 quality of life of stroke survivors .
the effectiveness of resistance training for the tongue results from both a central 
 ( neural ) and peripheral ( muscle mass ) effect13 . in the present study
, we confirmed that a structured 
 resistance - training program was effective for producing gains in strength ( 1 rm ) in the 
 tongue .
robbins et al.4 proposed that 
 improvements in swallowing function with resistance training are the result of both the 
 direct effects of training on strength and the effects of resistance training on the 
 neuroplasticity of the neural circuits for swallowing , including collateral sprouting to 
 areas affected by the stroke .
first , the sample size was small ; future studies with 
 larger sample sizes are therefore needed to generalize the results .
second , the recruited 
 participants included patients with relatively mild dysphagia who actively cooperated during 
 training .
, our study provides evidence supporting the inclusion of resistance training 
 of the tongue muscle in rehabilitation programs for stroke patients with dysphagia .
the 
 administration of this resistance training can improve tongue strength and general 
 swallowing function .
 [ purpose ] the aim of this study was to evaluate the effectiveness of a structured program 
 of resistance training for the tongue in order to improve swallowing function in stroke 
 patients with dysphagia . [ subjects and methods ] twenty - seven stroke patients with 
 dysphagia were randomly divided into two groups . 
 the experimental group participated in a 
 resistance - training program involving a 1-repetition maximum , with an intensity of 80% , 
 along with 50 repetitions per day each for the anterior and posterior regions of the 
 tongue . 
 both groups received conventional therapy for dysphagia for 30  min per day , 5 
 times per week , for 6 weeks . 
 [ results ] the experimental group showed statistically 
 significant improvements in both , the anterior and posterior regions of the tongue . in 
 contrast , the control group showed significant improvements only in the anterior region of 
 the tongue . in the videofluoroscopic dysphagia scale evaluation , 
 improvement was noted at 
 both , the oral and pharyngeal stages in the experimental group , whereas significant 
 improvements were only noted in the oral stage and total score in the control group . 
 
 [ conclusion ] our study confirmed that tongue resistance training is an effective 
 intervention for stroke patients with dysphagia , offering improved tongue muscle strength 
 and overall improvement in swallowing . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION