Good point, I have noticed considerable physiological changes as I have aged. I have to ‘warm-up’ for longer periods, and there have been occasions where playing ‘cold’ has proved very difficult.
You ask about exercises, there being any number of these designed to facilitate the improvement of response. However, the biggest change I found came from internal assistance and I don’t mean mental things like meditation.
Two things;
Every day I take essential oil and after a short period, all my joint functions improved by 50%. I used to take Udo’s Oil, but there are many cheaper and equally good alternatives. Most supermarkets sell essential oil (Sainsbury’s definitely).
The other thing is glucosamine sulphate, a naturally occurring amino acid that is proven to rebuild joint cartilage and tendons. I combine this with sulphur (also known as MSM), in capsule form, (there are several makes that stick them in the same capsule together).
You may think this is a load of old ****, but your finger joints are like elastic bands and the stronger and more supple the connective tissue, the faster and more fluid your playing response. I also run, lift weights, and do punchbag/boxing/martial arts training and at a bodyweight of 17st noticed the very definite changes since taking these supplements.