It might be your nerves not your muscles that need to heal.. The muscles may stiffen or weaken when they are not receiving the proper nerve signals. I know in my case, my calve muscles are weak, but it isn't due to the muscle itself needing to heal, it's the nerves innervating that muscle that need to heal.
So although it's good to use and stimulate the nerves, overdoing it could irritate them and cause more symptoms. In my own case, I haven't found overdoing it causes any permanent damage, but more fatigue, numbness, and tingling.
Another thing that might cause the symptoms you have could be the cold water. When I have been in cold water for an extended period, my muscles around the nerve damaged area cramp up.