Fibromyalgia – Why is Soleus Muscle Tone Important?

Fibromyalgia – Why is Soleus Muscle Tone Important?

Vital Motion develops and markets medical devices designed to stimulate and improve muscle tone in the soleus muscle of the calf. There are two muscles in the calf, both of which attach to the Achilles tendon, which also attaches to your heel bone (Figure 1). The large muscle on the back of your leg (gastrocnemious) allows you to stand up on your toes and is critical in walking, running, and going up and down stairs. The soleus muscle can seem at first to be less important, as it is a postural muscle which simply helps you stand upright. However, this muscle is quite remarkable as it allows you to stand for very long periods of time. Young military recruits, for example, can stand at attention for many hours due to the soleus muscle’s ability to sustain contractions for 12-18 hours or more without becoming exhausted.

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Figure 1. The soleus muscle and gastrocnemious are the two muscles in the calf. The gastrocnemius is a voluntary muscle, the one you use to stand up on your toes. The soleus is primarily a postural muscle, which provides support when standing quietly as well as serving to pump blood back to the heart.For those of us who are no longer teenagers, the ability to stand quietly for many hours has usually been lost. Over time, the soleus muscle loses its ability to contract continuously and so we rely more and more on our gastrocnemius to help us stand, but the gastrocnemius muscle fatigues quickly and find ourselves having to sit down and rest much more often than when we were young. In some people, this soleus weakness can occur when they are still in their 20s or 30s.If helping us stand quietly was the only role of the soleus muscle, there would be little concern about maintaining good muscle tone in the soleus, however, while we are standing (or sitting) the soleus is also responsible for pumping our blood back to our hearts. The soleus muscle contains large venous sinuses which slowly fill with blood when we are standing or sitting, and then periodically contracts to push this blood back up to the heart against the force of gravity – for this reason, it is often called the “second heart.” When the soleus muscle weakens, insufficient blood gets returned to the heart, and so an insufficient amount of blood is pumped out with each heart contraction. As a result, the tissues of the body become starved for oxygen and nutrients, and individuals in this situation begin to develop conditions such as chronic dizziness, blurry vision, cognitive difficulties, chronic fatigue, varicose veins, and many other symptoms associated with low cardiac output.

Mechanical stimulation of the soleus muscle has been shown to be able to significantly increase cardiac output by enhancing blood return to the heart. Research undertaken at the Westchester Medical Center in New York (1) showed that, for middle aged women undergoing mechanical stimulation of the soleus muscle, blood flow into the lower body (legs and pelvic region) increased by an average of 40%, while blood flow into the upper body (thoracic region) increased by an average of 17%.

Good soleus muscle tone is therefore crucial to our continued health, and for those who have poor tone in their soleus muscles, soles muscle stimulation (“SMS”) provides a convenient means to obtain both immediate relief from inadequate blood return to the heart, as well improved muscle tone over the longer term.

Click here to learn how the Hummingbird can increase soleus muscle tone.


1. Stewart, Karman, Montgomery, and McLeod. Plantar vibration improves leg fluid in perimenopausal women. AM J Physiol Regul Integr Comp Physiol 288:R623-R629, 2005

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