When we talk about compound exercises in fitness, there are actually two distinct phenomena both referred to by the term.
The first refers to multi-joint exercises: these exercises tend to be superior in building strength and muscle because they engage a lot of muscle at once and tend to work in basic movement patterns that you see in day to day life. That means GAINS. Additionally, because these movements work a lot of muscle all at once, they tend to have a pretty robust metabolic effect and can really get your heart rate up.
These multi-joint exercises are contrasted by single-joint exercises like the bicep curl: single-joint exercises are good for targeting specific muscles that may be difficult for the trainee to target otherwise with multi-joint exercises, and tend not to be nearly as demanding metabolically.
Multi-joint exercises are great. They’re the staple of all modern strength, hypertrophy, and endurance programs. In a well structured program, they should take up the bulk of your work and provide you with the bulk of your results.
The second form of compound exercise refers to two existing exercises that are combined together with magic wizard glue to create a new exercise. They might also be called complexes, though in general complexes contain a bunch of exercises (rather than just two) done in sequence with the exact same weights (barbell, dumbbells, etc.) without putting them down.
Unfortunately complexes are not always so great, and neither are the kind of compound exercise that’s just a two exercise complex. They certainly do have a lot going for them: you can train a lot of different muscles at once, resulting in an intense metabolic effect and additionally the ability to build a lot of muscle pretty quickly.
The problem with these types of exercises arise when they’re programmed poorly, or when there’s a vast difference in strength from one movement to another. Let’s take a very simple barbell complex I’ve used with my clients in the past:
Power Clean x5
Front Squat x5
Overhead Press x5
Seems great, right? You’re working practically every muscle in the body. The deadlift will work your hip extension muscles and rear core, the clean works the upper back and biceps, the squat works the knee extension and the forward core, and the overhead press works your shoulders and triceps. All that you’re really missing is your chest.
But can you see what the issue here might be?
The problem is that of these movements, some will be much stronger than others. In most raw lifters, the deadlift tends to be the strongest movement and the overhead press tends to be the weakest, simply because leverages and the amount of muscle that’s used in each movement are very different.
What this means is that you’re almost always going to be able to deadlift a lot more than you can overhead press. You could add extra reps to the deadlift like I did here to up the challenge a bit, but this can only be done up to a certain point.
Whichever lift is your weakest link in the chain is the one that all the other lifts have to work around.
This means that your ability to add weight to the other movements in this complex is limited by the shoulder press. Since many people can deadlift a lot more than what they can shoulder press, this means that whatever is a challenging weight for the shoulder press is going to likely be a trivial weight for the deadlift.
The same principle applies to lots of other movements as well. There’s compound exercises that are just upper and lower body movements paired, like a hammer curl with a lunge or an overhead press with a stepup. Sure, these exercises are tougher than either of their individual components alone are. But tougher doesn’t always mean better.
Let’s take, for example, a double dumbbell deadlift paired with a hammer curl. Chances are, you’re getting a good bicep workout but a bad deadlift workout. Training these two lifts together gets your heart rate up a little bit more, but it likely impacts your ability to add load to either of those exercises. The weight is going to be easy for the deadlift and you’re going to have to do more reps of it, and the weight is going to be challenging for the biceps but chances are that the act of adding a deadlift in between is going to tire you out quicker and reduce the number of total reps you could have done with the hammer curls alone.
The key aspect of any good training program is the ability to progress that workout over time, adding weight or repetitions. Sadly, primarily using complexes with movements of disparate strength levels means that over time the mismatch is going to grow worse and worse, and you’re going to get a lesser and lesser benefit from them. Since you’re not adding weight as easily, chances are you’re not stimulating the development of more muscle and strength.
That’s not to say you should never do them. Complexes are great for adding a little bit of challenge to a workout here and there, and the use of a few complex-type compound movements every now and then can certainly be great to add a bit of a metabolic challenge. However, to comprise a workout solely of complexes is likely to encourage training imbalances over time.
A better suggestion is simply to split those movements up, but keep them as a superset. If you supersetted hammer curls with barbell deadlifts, for example, you could use different weights for both exercises and thus ensure a better ability to progress your workouts over time while still keeping the workout relatively fast-paced.
Above all, never consider a workout’s value based entirely on its ability to cause you to sweat: what is needed to improve over time is not sweat, but instead increases in the amount of weight used or the number of repetitions performed.