Dips have been around for years. They even have specialized dips bars in gyms purely designed for performing sets of dips. Dips however are not shoulder friendly. As you lower yourself down, under full bodyweight, during the Dip exercise you put your shoulder capsule under huge amounts of strain. Basically the arms are not designed to go backwards in that way. Ever wondered why your shoulders are sore after performing Dips? It’s because you are stretching all your ligaments and the soft tissue of the shoulder joint. If you do Dips regularly, chances are, you may develop sloppy and unstable shoulder joints that are more likely to dislocate.
Sit Ups only perform 50% of the natural movement of the spine if you are performing them lying on the floor. If you are going to perform this exercise then at least Crunch over a Stability Ball to get the full range of movement.
Not only do Sit Ups seem counter intuitive to posture but they also don’t seem to line up with our natural daily movements.
Another reason is that sit-ups are hard on your back. They push your curved spine against the floor and work your hip flexors. When the hip flexors are too strong or too tight, they tug on the lower spine, which can create lower back discomfort.
One good alternative to Dips is by doing push ups and a good alternative to sit-ups is doing the plank exercise. They yield same effects and results but different methods, yet both safe and effective.
Also here are some other great resouces