An effect may be: unable to reproduce
A. Would be the answer I chose.
It said one of the following WORKOUT CHANGES, so I'm assuming that it doesn't want you to just stop. Different shoes may provide better support, bringing relief to the knees and allowing you to continue your walking workout.
That looks like Pseudostratified Columnar. Could be wrong but I'm 95% certain.
Hope this helps
Its main purpose is to restore partial flow of oxygenated blood to the brain and heart. ♥
So you won't sprain any muscles or hurt yourself.