The Superficial Front Line (SFL) (Fig. 4.1) connects the entire anterior surface of the body from the top of the feet to the side of the skull in two pieces – toes to pelvis and pelvis to head (Fig. 4.2/Table 4.1) – which, when the hip is extended as in standing, function as one continuous line of integrated myofascia.
The overall postural function of the SFL is to balance the Superficial Back Line (SBL), and to provide tensile support from the top to lift those parts of the skeleton which extend forward of the gravity line – the pubis, rib cage, and face. Myofascia of the SFL also maintain the postural extension of the knee. The muscles of the SFL stand ready to defend the soft and sensitive parts that adorn the front surface of the human body, and protect the viscera of the ventral cavity (Fig. 4.3)
The SFL begins on the tops of the toes. By the ‘everything-connects-to-everything-else’ fascial princi- ple, the SFL technically joins with the SBL through the periostea around the tip of the toe phalanges, but there is no discernible ‘play’ across this connection. Function- ally these two Anatomy Trains lines oppose each other, the SBL being responsible for flexing the toes, and the SFL taking on the job of extending them, and so on up the body. More practically, in postural terms, the dorsi- flexors act to restrain the tibia-fibula complex from moving too far back, and the plantarflexors prevent it from leaning too far forward.
Sagittal postural balance (A-P balance) is primarily maintained throughout the body by either an easy or a tense relationship between these two lines (Fig. 4.4). In the trunk and neck, however, the Deep Front Line must be included to complete and complicate the equation (see Fig. 3.38 and Ch. 9).
When the lines are considered as parts of fascial planes, rather than as chains of contractile muscles, it is worth noting that in by far the majority of cases, the SFL tends to shift down, and the SBL tends to shift up in response (Fig. 4.5).
The overall movement function of the SFL is to create flexion of the trunk and hips, extension at the knee, and dorsiflexion of the foot (Fig. 4.6). The SFL performs a complex set of actions at the neck level, which comes up for discussion below. The need to create sudden and strong flexion movements at the various joints requires that the muscular portion of the SFL contain a higher proportion of fast-twitch muscle fibers. The interplay between the predominantly endurance-oriented SBL and the quickly reactive SFL can be seen in the need for contraction in one line when the other is stretched (Fig. 4.7).
