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Hi there and welcome to Justanswer!!
It appears to me that your dog may have had an epileptic seizure. This is a condition that occurs from some trigger in the brain and causes either gran mal seizures or petite mal seizures which are smaller manifestations of this same disease. They can have one episode and never have another or they can have more episodes.It appears to me that max is having petite ma seizures especially if he comes out of this acting normal.
It is best to have your vet examine your dog to rule out any metabolic issues that could also cause seizures such as a liver issue. Once that is ruled out, your vet may choose to place your dog on antiseizure medication if your dog has more than one seizure per week. I say this because your dog could die during a seizure or suffer permanent brain damage if the seizure lasts a long time.
Have your vet examine your dog and they will tell you what to do. It seems unlikely from what you have described that this has anything to do with his muscular system.