I am a beginner player, just starting to speed up on some of my pieces. It seems my poor hands are not accustomed to this new exercise and started getting sore and stiff, making it hard to practice the next day. Maybe cuz I am post retirement age I just don't heal that quickly after a workout.
I thought I would share with you what has actually been working for me, however unproven it may be - contrast therapy. I have 2 bowls of water, one icy cold tap water, one hot tap water, and alternate putting my hands in each. (I wear rubber gloves when I do this as it is easier on the nails) : Cold 1 minute, Hot 1 minute, Cold 1 minute, Hot 1 minute, Cold 1 minute. I do this after every practice and this 5 minutes has been worth it as my hands are no longer giving me problems. But I do rather hope my hands get stronger soon so I don't have to keep doing this forever!