Similar to supersets, you combine several exercises that you do without a break. The difference is that all exercises are done for the same muscle group. Again, you don’t take breaks in between exercises, you perform them back to back. This technique is particularly popular in leg training, where you could combine for example squats, hack squats, leg press, leg extensions and walking lunges into a huge set.
Giant sets make sense primarily for training large muscle groups such as legs, back, chest or abs. Also for shoulders with their three muscle groups good combinations are possible. Here you dedicate one isolation exercise to each head of the shoulder muscle individually, and then perform a overhead press for a combined effort. In small muscles such as biceps or triceps giant sets should be used to burn the muscle out (e.g. as a finishing movement) – Fatality.
Order of exercises plays an important role. You should try to put exercises that need lots of coordination and concentration at the beginning of the giant set and choose the ones that are less demanding for last. For example you start out with free weights and end your giant set with machine exercises.
Forget that you can handle normal training weights in the follow-up exercises. This only leads to injuries. Again, check your ego at the door, the follow-up exercises are there to exhaust the muscle completely, not to set new personal records in training weight.