Effects of tongue strengthening exercises on tongue muscle strength: a systematic review and meta-analysis of randomized controlled trials

Tongue strengthening exercise (TSE) has been proposed as an intervention to increase tongue strength and improve swallowing. However, clinical evidence of its effectiveness is lacking. In this review, seven databases were searched from inception to September 30, 2021 for randomized controlled trials that compared tongue strengths between the TSE intervention and control groups, obtained from maximal tongue elevation peak force in kilopascals (kPa). The Cochrane risk of bias tool was used for quality assessment. In total, 12 studies with 388 participants were included. The pooled meta-analysis demonstrated that the anterior tongue strength (ATS) (MD = 5.34 kPa; 95% CI 3.28–7.40; I(2) = 71%) and posterior tongue strength (MD = 8.12; 95% CI 3.45–12.79; I(2) = 90%) were significantly higher in the TSE intervention than that in the control group. Among healthy participants, subgroup analysis showed that TSE had improvements on ATS in all age groups, with the greatest improvement in old people (≥ 65 years) (MD = 8.01; 95% CI 4.39–11.64; I(2) = 30%). Meta-regression analysis revealed a nonsignificant trend toward greater improvement on tongue strength with increasing TSE duration. This study provides positive evidence that TSE may be beneficial in improving tongue strength and could be applied for adults, especially healthy older adults.