Question
Hello,
  I've recently been diagnosed with a herniated disk in my lower back, which gave me great pain in the front of my lower right leg and front part of my ankle.  While physical therapy has relieved most of the pain, I will also be having a steroid epidural injection to further relieve the inflamation and pressure to my sciatica nerve, thus allowing me to resume most normal activities.
  I mention this to give you the complete picture.  However, I have noticed that since this started, I am unable to stand on just the heel of my right foot....and likewise, when I walk, my right foot tends to almost "flop" flat down, rather than performing a normal heel-to-toe movement.  Is this related to the nerve being pinched by the herniated disk??  
  Just as one more bit of info, I did some seated leg presses at the gym with some fairly heavy weight...but just one set of 8.  Coincidentally or not, the herniated disk problem developed about 48 hrs. later, as did my weakness with my ankle.

Answer
The peroneal nerve is the culprit. It is a branch of off the sciatic nerve.It is probably related to the ruptured disc. You may have pinched the peroneal nerve on the leg press machine. All nerve injuries need a good evaluation to prevent additional disability. Damaged nerves are very slow poor healers
Unless you see daily improvement you need to get the drop foot braced and get aggressive physical therapy to help allow full recovery
Good Luck Again
Dr George Tsatsos-Chicago & Elmhurst Podiatrist
Board Certified Foot & Ankle Surgery & Orthopedics
NOT ADVICE_JUST INFO FOR ALL