I have been training for a marathon and am on week 8 of a 16 week plan. I have been running for about 20 years so I am not a novice runner. Recently, I started experiencing foot tingling, followed by numbs in my second toe and then the entire foot. It used to be in my left foot only and now it is in my right as well. I went to a podiatrist who suggested a foot pad under the metatarsal but it caused tremendous pain in my foot. I feel like I am running on wood by the end of a 10 miler. What am I to do.
I am going to make some assumptions that your 20 years of running have not been casual but a long love affair with the sport. You have no doubt experienced some of the common running injuries like shin splints, runner's knee, ITBS, AT, PF, etc., and are not about to give up over a little tingling in your feet. You've worn out scores of shoes of different manufacture and technology, so you would know if some recent purchase was responsible for the problem you have now. I'll continue to assume you tried different lacing methods to make sure circulation was not being cut off to your feet from a bad tie.
The important information within this question is that your feet are affected but you do not mention any other body part being affected. I mention this because Sciatic nerve impingement in the lower Lumbar area and occasionally Piriformis syndrome can produce this symptom, but you are most likely to have similar sensations throughout the leg and buttocks as well. Restriction to the foot is an important clue and nerves are likely to be involved (assuming circulation is normal as addressed above).
I've had experiences like this related to a neuroma, which is an enflamed encapsuled nerve between the metatarsals. These are known to affect mature runners because it can take years of abuse to create them. If you have a foot condition or shoe that is not optimum but tolerable, a neuroma can continue to grow until the pressure begins to cut off sensation in areas of the foot affected by that nerve. Usually this will be accompanied by sharp pain between the metatarsals so I am not completely comfortable with this as the only possible diagnosis.
Here is where we need more information about the structure of your foot versus your shoes and socks. I once had a situation like yours develop during a marathon because of my attempt to control a neuroma with taping, only to find the circulation to the foot had been cut off so that numbness spread from my toes rearward, and I had to stop and remove the taping at mile 22 to finish the race, costing me a qualifying time. It was worth the loss at the time because I thought I would lose the foot if I continued, so I sympathize.
Often metatarsal pads are used to reduce pressure on a neuroma, but depending on the location of the inflamed nerve it can make them worse, so lets take a look at your foot structure to determine this. Are your arches of normal height? With your feet placed flat on the floor, can you slide at least the first joint of your first two fingers underneath the center of the arch? If not, some other issues come into play, including lack of tonus in the TIbialis Posterior muscle and possible Morton's Toe (short 1st metatarsal). I assume your podiatrist would have informed you if either of these scenarios were true.
If the arch is low and it is due to the TP muscle, you must first release this muscle so it can be conditioned to its normal strength. While we are doing that you can determine if excess pronation during running is tiring the TP muscle, and if the cause of this excess pronation is foot structure or problems with the hip or knee. This can be a "chicken or egg" question because foot structure can lead to hip problems and vice-versa, although it is more likely to be the other way around. To determine foot structure as the cause, I'll include a link with illustrations here... http://www.triggerpointbook.com/mortons.htm
While you may think this would have been covered by your podiatrist, the few who are savvy about Morton's and how to deal with it would not be surprised to find the orthotic you were offered did not work. If the pad used was under the 1st metatarsal, there are issues with that bone, possible spurs, and the fatty pads underneath that can render the treatment useless and increase your pain. At this point I need more feedback from you to proceed, but we can digress for a moment to cover some issues on the back burner.
While seated upright on a solid chair, is it possible for you to cross one knee over the other without substantial tightness or pain deep in the buttock? Try leaning your chin forward to see how close it can come to the top knee, and try this on both sides. Excess tightness in the hip rotators, particularly the Piriformis muscle, would make these maneuvers difficult and/or painful, and would be another important clue. At his point it is important to know that the condition or structure of your foot can cause a problem up in the hip that involves the extent of foot pronation/supination during your stride, so we'll hold back on the causatives for now until all these clues have been established.
Looking forward to your reply...
This happened to me about 10 years ago. My toes would go numb after 4- 6 miles.The guy at my running shoe store told me your feet change when you get older. They are less pliant and they swell up more. He suggested I start wearing running shoes a whole size bigger than my regular size. It totally worked. My toes stopped going numb (and I have never had a toenial issue or a blister.) Good luck.