An earlier Gray Institute blog discussed the need to go “beyond the anatomical model” in order to appreciate how muscles work in function. The conventional approach to muscles looks at the joints that the muscle(s) crosses and describe what happens if the muscle shortens. Often this perspective is limited to a single plane of motion. The Gray Institute’s approach (as discussed in that blog) is to focus on muscle activity that is 3D, econcentric, synergistic, and task-specific. This series of blogs will focus on the influence of muscles at joint not crossed by that muscle. Specifically, joints where the muscle attaches to one of the bones that make up a joint, or “one joint beyond”.
CONVENTIONAL PERSPECTIVE
Muscle: Soleus
a Concentric Acceleration Eccentric Deceleration
Sagittal Ankle Plantarflexion Ankle Dorsiflexion
Frontal Subtalar Inversion Subtalar Eversion
Transverse Hip External Rotation Hip Internal Rotation
When our perspective expands beyond the joints crossed (ankle and subtalar) the role of muscles (and our options for training/ rehab of those muscles) becomes much more powerful. Since the Soleus muscle attaches to the tibia and fibula the “one joint beyond” perspective means that we must consider influence of the soleus on the knee.
When the foot is on the ground during function, if the Soleus pulls back on the lower leg (ankle plantarflexion), then the knee will extend. This function of the Soleus at the knee occurs during ambulation when ankle dorsiflexion is occurring as the body moves over the foot. The Soleus slows down this dorsiflexion by controlling the forward movement of the lower leg. As the trunk and femur continue forward, knee extension is created. So during walking, the soleus is one of the primary extensors of the knee. In addition, since the Soleus controls eversion of the calcaneus at the subtalar joint, it will control the inward movement of the knee joint in the frontal and transverse planes: preventing, and then reversing, the movement of the knee into a valgus position.
Moving “one joint beyond” down the Chain Reaction is slightly more challenging, but no less important. Since the Soleus attaches to the Calcaneus, the “next joint” is the mid-tarsal joint of the foot. So the rearfoot becomes the proximal “bone” and the forefoot becomes the distal “bone”. At the Gray Institute, we describe the mid-tarsal motion created by the rearfoot moving on a fixed forefoot as driven “top-down”. When the proximal bone of an extremity joint moves on a fixed distal bone, the joint motion is opposite the proximal bone motion. This means that if the rearfoot everts, then the motion is inversion at the mid-tarsal joint in the frontal plane.
This chart focuses on what motions of the calcaneus that the Soleus influences and the resulting “one joint beyond” affect at the mid-tarsal joint.
The Soleus will decelerate rearfoot …
Sagittal Plane Frontal Plane Transverse Plane
Dorsiflexion Eversion Adduction (Int Rot)
Therefore the Soleus will decelerate these motions at the mid-tarsal joint.
Plantarflexion Inversion Abduction (Ext Rot)
The analysis movements of the 3D Movement and Performance System are designed to assess ankle and foot motion driven both top-down and bottom-up during global movements in each plane. The results of the analysis movements will provide strategies for challenging all the functional capabilities of the Soleus.