To isolate the soleus during plantarflexion testing, what knee position and resistance location are used?

To isolate the soleus during plantarflexion testing, what knee position and resistance location are used?

• A. Knee flexed to about 90 degrees with resistance at the forefoot
• B. Knee extended with resistance at the heel
• C. Knee flexed with resistance at the midfoot
• D. Knee flexed to about 45 degrees with resistance at the toes

Answer: (A)

Isolating the soleus relies on reducing the contribution of the gastrocnemius, which crosses the knee. When the knee is kept flexed at about 90 degrees, the gastrocnemius is slackened and its role in plantarflexion is minimized, so the soleus does most of the work during the test. Applying resistance to the forefoot provides a plantarflexion force through a favorable lever arm that emphasizes the soleus’s action via the Achilles mechanism. If the knee were extended, the gastrocnemius would contribute more to the movement, and different resistance locations (like the heel) could alter the mechanics, making soleus isolation less reliable.

Isolating the soleus relies on reducing the contribution of the gastrocnemius, which crosses the knee. When the knee is kept flexed at about 90 degrees, the gastrocnemius is slackened and its role in plantarflexion is minimized, so the soleus does most of the work during the test. Applying resistance to the forefoot provides a plantarflexion force through a favorable lever arm that emphasizes the soleus’s action via the Achilles mechanism. If the knee were extended, the gastrocnemius would contribute more to the movement, and different resistance locations (like the heel) could alter the mechanics, making soleus isolation less reliable.