What causes drop foot?

Hi Mona, the heavy foot fall mentioned in the video is due to weakness in Tibialis Anterior. Drop foot is a little more severe and involves damage, or at least dysfunction, of the common fibular nerve. This usually occurs due to impact or prolonged compression of the nerve where it passes below the proximal fibular head on the outside of the lower leg. Neurological testing can be used to confirm this. Hope this helps.