The strength of the AT force field is very much determined by one's own mind; if there isn't an attack using the same medium, it is essentially impossible to damage it.
However, the Inner Breath cultivated by martial artists actually contains some of their own willpower. This is not apparent in the initial stages, but as one progresses to the Energy Cultivation Realm and the Path Entry Realm, this characteristic becomes increasingly prominent.
After all, martial artists in the Path Entry Realm can use the energy within their bodies to draw upon the Spirit Energy between heaven and earth. If the energy within doesn't contain their own will, then how could it possibly draw on the Spirit Energy of the world?
The second and fifth members of the Simon Family were preparing to use knives to help break through the opponent's AT force field, but just as they were about to swing their blades, the third brother suddenly spoke, "Energetic transmission."