Evaluating Effectiveness of Articulation Practice with Tongue-twister Movement Distance Using Ultrasound

Deterioration of oral function can impair articulation, making it essential to evaluate tongue movement during articulation training. Previous reports have indicated an improvement in motor speech disorders, such as glossectomy-related glide issues, through rapid speech exercises, suggesting the potential benefits of non-invasive training. This study aimed to investigate the effect of tongue training on oral function using tongue twisters in healthy Japanese-speaking women. The participants performed tongue twisters designed to engage both the tongue tip and root, with data collected at baseline, 1 month, and 7 months. Participants were required to complete sentences involving the repeated use of /ta/ and /ka/ sounds. This training was conducted 5 times per week for 1 month. Oral diadochokinesis (ODK) was used to measure the number of repetitions per second of each sound, while ultrasound imaging captured the vertical motion of the tongue during pronunciation. The ODK test was used to evaluate speed and regularity of articulatory movement, and ultrasound measurement to assess vertical motion dynamics of the tongue during pronunciation of /ta/ and /ka/. The results indicated a significant improvement in the number of repetitions per second for both /ta/ and /ka/ after 1 month of training. This increase in repetition frequency was maintained for /ta/ even after 7 months, whereas /ka/ showed no further increase in repetition frequency beyond the 1-month mark. Despite this, vertical distance of tongue movement decreased significantly for both syllables after 1 and 7 months. This suggests that /ta/ benefited from both increased efficiency and speed, whereas /ka/ prioritized refined motor control over frequency. The complexity of posterior tongue elevation in /ka/ may require greater precision, limiting increase in repetition despite improved efficiency. This study demonstrates that regular tongue-twister training effectively refines oral function in young women, with sustained benefits over time. The simplicity and accessibility of this method make it a promising approach to maintaining and enhancing oral and articulatory function.