Joe Weider’s staggered sets principle involves alternating small muscle group exercises into a regular large muscle group workout in order to do two things. It allows the large muscle to rest while the small muscles are being worked. Secondly, it can be used to bring up a lagging body part by shocking a muscle – allowing the completion of copious sets that otherwise would never get completed.
Arnold Schwarzenegger is known for beginning or finishing a workout with an insane amount of abdominal work such as 10 minutes of roman chair sit-ups or 1000 crunches. Very few people have the mental stamina to do this amount of training set after set, rep after rep, as the muscles burn like they have been set on fire.
Another approach is to stagger abdominal work in between potentially each set while training larger muscles. For example, while training chest, back, or legs try various combinations of exercises you can alternate – a set of crunches with bench presses, leg raises with barbell rows, or roman chair sit-ups with back squats. Training the abdominals in this fashion can literally add 20 to 30 sets of work being completed. It also gives you a chance to rest and recover from a set of heavy bench presses, barbell rows, or squats which sometimes require 2 to 3 minutes or more of rest.
Staggered sets can also be used to bring up other small muscle groups or areas lagging behind such as rear delts, biceps, or calves. Try scheduling these smaller muscle groups with large antagonistic muscle groups – chest and biceps, back and triceps, or shoulders and calves – for several weeks and see what happens.
If anything, staggered sets will really confuse the crap out of the muscles and a variety of fun workouts can be designed using this principle. The Weider training principles have endured the test of time for a reason – they work.