I did my exercises and then took a long hot shower. After exercising, I showered for a long time in hot water.
These are options with the past perfect:
After I had done my exercises, I took a long hot shower. Before I took a long hot shower, I had done my exercises. When I had finished my exercises, I took a long
They all have basically the same meaning, but the first two are unnecessarily abstract, and it's true that doneis a bit of a strong word. It's best to keep things simple and clear.