How to improve baby finger's extension and flexion? How to relax it? How to stretch it?

Question

My baby finger has not become relaxed enough due to wrong technique in tennis, too much stress on it and more here. The only moment I can feel the toughness is when I am totally relaxed like after sleeping so it does not limit my activities at all but I don't want to get it bad neither so important to learn to get it more relaxed. So

How can I improve baby finger's extension and flexion? How to relax it and how to stretch it?

Hand's 2-5 fingers flexion/extension

According to this, normal ROM values are 85-105 degrees for the flexion and 20-30 degrees for the extension. In contrast, my ROM values are 85 for the flexion and 70 degrees for the extension.

Related threads

1. Preparing fingers for intensive sports requiring hands a lot?

2. Safe volley grip and serving grip in tennis

Answer 1

You can train the twisting muscle by doing tricep training where you lift a bar above your head and let it go behind your back over your head. Now the key is the grip: you need to inverse your grip to get the twisting muscles activated! I was able to recover from the continuous pain in the twisting muscle caused by golf, tennis and climbing by inventing the totally new training with bar over the head with inverse grip (for the traditional tricep training)!

Basically the other muscle group can be seen as opposing muscle group on the other side: anterior/posterior pair

where I removed the pain on the other side by forearm training illustrated in this answer here.