noun
soleus muscle
Anatomical term for the calf muscle beneath the gastrocnemius; named for its resemblance to a flatfish (ヒラメ).
ひらめ筋はふくらはぎの深層にある筋肉です。
The soleus muscle is a muscle located deep in the calf.
ランニングでひらめ筋を痛めた。
I injured my soleus muscle while running.
The gastrocnemius muscle, the larger, more superficial calf muscle that forms the bulge; the soleus lies underneath it.
From ひらめ (平目・比目魚, 'flatfish, flounder') + 筋 (きん, 'muscle'), so called because the muscle's shape resembles a flatfish.