Good evening. I am a neurologist from Cleveland, OH and will give you a few ideas, however, the computer is right in covering the base of MS in someone your age with those types of symptoms. It needs to be addressed. There are some other things to think of that can give similar symptoms but here is the problem with most of the MS mimickers ...most everything from B12 deficiency to sarcoidosis, to STD s, and metabolic diseases that one could imagine giving symptoms like that by and large occur over both sides of the body and do not stay fixed in one limb for very long. Of course, if you also had some back pain to tell us about one could also imagine some sort of nerve root being compressed at the L4 or L5 level. However, you would ve come clean with the back pain right away at the beginning of your presentation if it would be important enough to cause these constant symptoms so I m assuming back pain is not really a problem. Other things such as transverse myelitis (TM) which is similar to MS but different could cause a focal finding such as what you describe but there would also be expected other findings such as weakness and bowel/bladder incontinence and so forth....back pain is a common finding in TM. However, muscle cramping is frequently seen in TM as well and usually that early on in MS. Now, the swim class. I do certainly like the idea that all this could be due to using fins and doing an exercise which is typically pretty strenuous for most people and I would be very willing to accept this as an explanation. Know how to find out quickly? STOP THE CLASS AND WAIT A COUPLE of weeks. Get some massages in the calf, the foot, and the ankle, and see what happens to your symptoms. Perhaps, in some way you are ASYMMETRICALLY using your legs and feet. If you are right dominant then, maybe you are favoring that side and struggling a bit more on the left making the calf, leg, and foot muscles do a lot of compensatory work that are just making it sore. Also, track the intensity and localization of your symptoms while you are in the swim class, wearing the fins, or if the symptoms don t develop in the water, how long after do they develop after the class? Are they most intense immediately following and then, dissipate as the day goes on? Are there other situations such as wearing dress shoes, wearing panty hose, and so forth where you ll notice symptoms at the time or shortly thereafter? If you d like to ask me further questions directly on a 1-1 basis here on the network please contact me @: bit.ly/drdariushsaghafi. I d be very glad if you kept me in the loop and let me know what the final diagnosis is here once you ve seen the neurologist if you decide to keep me guessing as it were! LOL! My email is drdar@pobox.com. If this information is of any use to you would you do me a favor and rate the question with STARS and maybe even a little feedback...especially if you liked any of my bad jokes....I m trying to keep the good ones to reuse...and find modifications to the bad ones to make them good! ROFL! Cheers my dear....for a wonderful Holiday Season full of GREAT NEWS in your future.