It has been shown in studies (Vico et al, 2014; Alghadir et al, 2015) that tongue position contributes significantly to postural stability and potential muscular strength. Why is this? It’s because the tongue is part of a myofascial chain called the Deep Front Line. Myofascial chains are lines of pull throughout the body which distribute strain, transmit force and affect the structure and function of the body. The theory of the myofascial chains help manual and movement practitioners explore how one structure affects other distal (further away) structures in the body.The line we are discussing, the Deep Front Line, runs from your head to your feet and is one of the main stabilizing chains of the body.
In a proper position pressing up against the hard palate, it provides stabilization down the chain and the surrounding muscles will have less of a stabilization role and are able to contribute more to lifting the weight.
The time you go to the gym or lift something heavy, try this out. Compare your strength with your tongue on the bottom of your mouth versus pressed up against the roof. Try to firmly (but not overly so) maximize the surface area the tongue covers.