How to Avoid Shoulder Injury when doing Dips and Sit Ups?

Question:

Thought you had mentioned in some previous emails that the dips and sit ups could lead to shoulder injury. Why are you now encouraging your readers to do them ? 

Answer:

My recommendation is to keep your shoulder extension to less than 45 degrees. You can do this by modifying your dip technique or leavening the range of your dip.