I was hoping that you could give me more information which is why I sent you an information request, but I dont' want you going without any answer.
Often dogs will move slow if they have an issue with the anal glands. When the gland is full, walking pulls the skin over the glands and can cause discomfort. Since he is 7 years old, I am figuring you have some knowledge of these, but just in case let me give you that information. The anal glands are 2 sacs on either side of the anus at about the 4' o'clock and 8 o'clock positions. If your dog is continually licking their anus and dragging it, it could also indicate that they are full. This problem can usually be resolved by emptying out the glands. To empty them or express them, you will want to cover the area with a tissue and press your finger on the dog's anal glands with an upward motion. A foul smelling liquid should come out. If nothing comes out and your dog appears to be in pain, you should take him to the Vet. Your vet can do this easily, as he is experienced at it. Excellent site on anal glands
Another reasons a dog might be walking gingerly would be a disc issue. Dogs will move and get pain one time but not the next and they can not figure out what movements causes the pain and thus walk slow to try an avoid discomfort. An intervertebral disc that has slipped or ruptured up into the spinal canal causes inflammation of the spinal cord, which in severe cases causes paralyses of the rear legs. Poodles are prone to disc issues. You can read about this here:
If your dog has had an unusual treat of fried or fatty foods like chicken skin, pork, bacon, etc, that could lead to pancreatitis or a touch of stomach upset. A dog will often walk slow with upper abdominal pain which comes with pancreatitis and stomach upset. They might assume a prayer like stretch with their rear in the air or arch the back. Pancreatitis is an inflammation of the pancreas. The pancreas is a gland that produces and releases enzymes into the digestive track that aid in the digestion of food. When these same enzymes are activated while they are still in the pancreas, inflammation occurs and the enzyme start "digesting" the pancreas itself. Symptoms of pancreatitis vary but include vomiting, diarrhea, anorexia, weakness or collapse, dehydration, shock, fever, depression, and upper abdominal pain. A dog may indicate abdominal pain by acting restless, panting, crying or wincing when picked up, shaking, standing with an arched back, or lying with the front end down and the rear end elevated
You can read about it in detail here:
Now a pulled or strained muscle might cause a dog to move a little slower but often when a dog has a soft tissue injury they will have a limp. It is not unusual for a dog not to cry even if he has pain. Dogs try not to show weakness until they can't suppress it.
As long as he is eating and drinking and eliminating relatively normal, you can try and keep him inactive as possible (crating works well for this) to give a possible injury time to heal.
I hope this information is helpful to you. If you would like any additional information or have more questions please don’t hesitate to press the reply to expert or continue conversation button so I can address any issues you still have . If you do find this helpful, please take this opportunity to rate my answer positively so I am compensated for my time.