Do this exercise slowly at first and gradually increase it until you notice any tension in your hand, arm or shoulder. Slow down just enough so that you can stay relaxed and do the exercise there.
On the third string put your fingers on the 5th, 6th, 7th and 8th frets and repeat the following combinations.
Do the same exercise in different positions and on different strings ensuring that the timing is spot on and that each note is as clean as all of the others.