I am a beginner at Blender and was following a tutorial that showed how to create a character with a rig and animate it. However, I have come across a problem I can't seem to fix. When I bend the arm for a running pose, the mesh at the elbow looses its volume. I have posted a screenshot below to show the problem.
Blend File: https://www.dropbox.com/s/kui3d18refgecde/charbendingsolutiontry.blend?dl=0