Hi, Nathan here, and welcome to my tutorial on "How To Strengthen Your Fretting Digits".
Disclaimer: by no means am I an advance guitar player - I have been playing on and off for the past 5 years and am gaining greater experience by the day.
To build up my muscles in my fingers, and as a warm up exercise, I like to play the beginning to the Muse: "Knights Of Cydonia".
This whole excerpt relies on the effect of tremolo, which is created by bending the string at a high frequency.
Go through the tab first to make sure you can it properly, and get familiar with the song here:
As you can see the excerpt relies heavly on just two strings. Instead of using all my fingers to play the tab, I just focus on using one mainly. To achieve this, just slide your finger your currently working on, down the string to hit the necessary notes. The strength needed to bend the strings while hitting the notes builds up the strength in your fingers.
Now my Pinky is one of the strongest fingers of my fretting hand - and the rest of my fingers are benefited with better accuracy and strength when playing licks or solos. Enjoy cracking open nuts with your harda-s pinky!