Effects of directional exercise on lingual strength

Purpose: To examine the application of known muscle training principles to tongue strengthening exercises and to answer the following research questions: (a) Did lingual strength increase following 9 weeks of training? (b) Did training conducted using an exercise moving the tongue in one direction result in strength changes for tongue movements in other directions? (c) Were differential training effects observed for participants completing exercises sequentially (in isolation) versus concurrently (several exercises in combination)? (d) Were strength gains maintained after exercise was discontinued? Methods: Participants were 39 healthy adults assigned to sequential or concurrent lingual strength training. Lingual exercise (elevation, protrusion, and/or lateralization) was conducted for 9 weeks, with lingual strength and cheek strength (control variable) assessed weekly. Results: All lingual strength measures increased with training, but cheek strength remained unchanged. Training effects were not related to training condition (sequential vs. concurrent), nor were specificity effects observed for direction of exercise. Significant decreases in lingual strength were noted 2-4 weeks after exercise was discontinued. Conclusions: The findings replicate those of earlier studies demonstrating that lingual strength may be increased with a variety of exercise protocols and confirm that detraining effects may be observed when training is discontinued. The findings further suggest that the lingual musculature may demonstrate less dramatic training specificity than what has been reported for skeletal muscles.