Whether for performance gains or as part of rehab for a painful Achilles, strengthening of the soleus muscle can be a highly beneficial addition to any runner’s strength training program.
Despite popular belief, the soleus muscle of the calf complex actually contributes more to force production during running than the gastrocnemius, essentially because during running it deals with the loads whilst the knee is bent. Research suggests the soleus produces up to 50% of the total vertical support; to put that into perspective, whilst the gastrocnemius produces forces of about three times your body weight during running, the soleus produces around eight times your body weight.
To target the soleus when you do your calf raises, studies have shown that your knee needs to be bent to at least 80 degrees. The most practical way of achieving this is performing the calf raises whilst seated (maintaining a deep bend in the knee whilst standing can put unnecessary strain on the knee).
NOTE: In cases of Achilles tendinopathy where the aggravated part of the tendon is close to the attachment point on the heel (referred to as insertional Achilles tendinopathy), allowing the heel to drop over the side of a step during calf raises may actually delay recovery. See our other video: “Seated Calf Raise for Runners – No Step.”
More details at ww.sportinjurymatt.co.uk.