Many coaches swear by compound exercises. But why and are these indeed superior to isolation exercises?

Key points:

1. Compound exercises, or compound exercises, are usually the foundation of a muscle growth training program. And rightly so: (heavy) compounds disrupt homeostasis more than isolation exercises, they train several muscle groups at the same time, including stabilizing muscles, and because you can perform them more heavily, you build up more maximal strength.

2. However, you should also do isolation exercises if you want to fully train every muscle group.

3. Make compound exercises the basis of your training (2/3 to 3/4) and supplement it with isolation exercises (1/4 to 1/3).

WHAT ARE COMPOUND EXERCISES?

Compound or multi-joint exercises are exercises that involve two or more joints. In other words, exercises in which you train multiple muscle groups at the same time.

In addition, compound usually means that you perform the exercise with free weights, so with barbells or dumbbells. As a result, you also train stabilizing muscles, which are virtually unaffected during isolation exercises, but also during mechanical compound exercises.

Some only classify the “big lifts” with barbells (bench press, squat, overhead press, row and deadlift) to compound exercises, but this definition is actually too narrow. After all, a dumbbell shoulder press is not inferior to the variant with the large bar in terms of compound content. Although the latter may look more impressive.

There is some controversy about the conventional deadlift. While an excellent strength exercise, it would overshoot its mark purely for muscle growth. While the exercise is effective, it may not be in proportion to the central fatigue it produces. But let’s leave this discussion for now.

In isolation exercises, on the other hand, you only train one muscle group, for example quadriceps with leg extensions and biceps with biceps curls.

WHY ARE COMPOUND EXERCISES IMPORTANT?

Compound exercises are seen as the key to muscle growth: if you want to get big, you have to do big, heavy exercises.

Although almost everyone will intuitively agree (including us), it is not easy to argue clearly why this is the case. Coach, author and speaker Mike Israetel:

Compound free weight exercises just work better than everything else, for reasons I’m still not clear on. I’m interested in intellectual philosophical debate as to why compound exercises work better. I’m not interested in debate that claims they don’t. ^[ i ]

According to Israel’s colleague Scott Stevenson, there is simply a correlation between muscle growth and how hard an exercise feels, how much it asks of you:

If you ask people to do either squats or leg extensions for quads, the people who choose squats are very likely going to build the biggest legs. ^[ ii ]

But what factors underlie this logical-sounding correlation?

HEAVIER = BETTER?

A frequently heard argument for doing compound exercises is that you can perform them heavily and therefore apply more overload. And overload is the most important condition for muscle growth, from a training point of view anyway.

However, the argument is not (completely) correct. Yes, because several muscle groups work together in compound exercises, you can perform them much heavier (safely) than isolation exercises. But using heavy weights is in principle not a condition for creating overload. Overload is increasing the training load by increasing weight and/or the number of repetitions – regardless of whether you use heavy weights (few reps) or light weights (many reps). Because you can also build muscle with light weights, as long as you make enough effort during your sets (i.e. train until close to muscle failure). Overload is therefore not the same as ‘more heavy load’.

It is true that with heavy weights you have to make less effort (relative intensity) to achieve muscle growth, compared to light weights. To put it more simply, with heavy compounds you can safely stay away from muscle failure, while with light weights you have to train to muscle failure to achieve the same stimulus ^[ iii ] . The latter can cause quite a bit of central fatigue and thus (unnecessarily) affect your recovery capacity and training performance. You should not train compounds to muscle failure, from the point of view of injury prevention, apart from the fact that this is not necessary.

In addition, it is probably important for complete muscle development that you use different rep ranges and therefore also do work in the range of roughly five to ten repetitions, with heavy weights. For that reason alone, your training program should already include at least some compound exercises (isolation exercises do not lend themselves to very heavy weights).

A specific advantage of compounds with heavy weights is that smaller, stabilizing muscles have to do a lot more work, for example to keep you in balance. With light weights or with isolation exercises this is not the case, or much less so. Thanks to heavy compound exercises, you can therefore also optimally develop those smaller muscles.

Finally, heavy weights are also much more efficient for developing pure strength. It is not without reason that powerlifters almost exclusively do the ‘big lifts’. Yet this is not really a valid argument for bodybuilders. As a bodybuilder, muscle growth is your only or by far your most important goal and strength gain is ‘only’ a consequence of that muscle growth. If you train with lighter weights, you can theoretically become just as muscular as with heavy weights, although you will develop less maximal strength.

MORE TESTOSTERONE = MORE MUSCLE GROWTH?

Another alleged benefit of compound exercises is the so-called hormonal response during exercise.

Strength training acutely increases the values of the anabolic hormones testosterone, growth hormone and IGF-1 ^[ iv ] and this occurs to a greater extent in compound exercises than in isolation exercises ^{[ v ] [ vi ]} .

Still, that hormonal response probably has no direct effect on muscle growth ^[ vii ] . Perhaps it mainly compensates for another hormonal response during strength training, namely the increase in the catabolic hormone cortisol (aka the ‘stress hormone’). And with large exercises with heavy weights, more cortisol is also released than with small exercises with light weights. One cancels out the other, it seems.

MORE DISRUPTION = MORE MUSCLE GROWTH

It is clear that compound exercises work well for muscle growth, but we have still not found the real cause. This probably lies in the fact that compound exercises disturb homeostasis (the internal balance of your body) more than doing other exercises ^[ viii ] .

Disruption of homeostasis through strength training and the resulting muscle damage is seen by the body as a reason to prepare for the next overload. The recovery of the muscle tears goes beyond the starting level. This makes the muscles bigger and stronger.

Mike Israel on this:

Compound moves just create more damage and disruption than isolation moves do, which also means they probably help you grow more. Now, damage isn’t the only factor in growth, but it’s likely an important one ^[ ix ] .

And:

Because compounds probably cause more damage, more tension, and more stretching under load, they are probably on average more effective at muscle growth than isolations ^[ ix ] .

All in all, you could say that overload resulting from compound exercises has a greater impact on muscle growth than that from isolation exercises. In jargon: compound exercises have a greater Raw Stimulus Magnitude (RSM).

EFFICIENT

An undeniable advantage of compound exercises is that they are highly efficient.

First of all, because you train several muscle groups at the same time and therefore save a lot of time. With pull-ups and rows, for example, you train just about all the muscles in the back, plus the biceps. Try training all those muscles with loose, isolating exercises. You would then not only lose a lot more time, but also demand a lot more from your recovery capacity. After all, you then need much more volume (exercises and sets) to fully train your back, even though those sets are less tiring in themselves than the sets of a compound exercise.

In addition, compounds improve so-called intermuscular coordination, simply put the cooperation between muscles, and they improve your overall movement and keep your body in balance. Things that can be very useful, especially for novice strength athletes.

Finally, you also burn more calories with compound exercises than with insulating exercises, but for a bodybuilder that is only a nice bonus in the cut.

All in all, compound exercises offer undeniable advantages, even if they are not all equally clear yet. Therefore, compound exercises should form the basis of a training program aimed at muscle growth.

WHY ALSO ISOLATION EXERCISES?

Despite the importance of compound exercises, isolation exercises also have their place in a well-thought-out bodybuilding program.

Isolation exercises can be performed with free weights as well as with machines. Machine exercises are the most isolating: they disable almost all other muscle groups in favor of the target muscle.

META-STUDY

According to a meta-study of 7 studies, by muscle growth expert Brad Schoenfeld, isolation exercises are just as effective for muscle growth as compounds ^[ xiii ] . Big caveat: 6 of the 7 studies looked at small muscle groups, namely biceps or triceps. The other study looked at the quadriceps ^[ xiv ] . So there is no research available on exercise on muscles such as the shoulders, glutes, hamstrings and calves. In addition, the isolation exercises could come out as a loser.

THE PRACTICE

Looking at practice, we can say that isolation exercises are functional for the following reasons:

To fully develop a muscle group, you will have to bombard it with several exercises. Compound exercises alone are usually not sufficient. For example, while squats are extremely effective for the quadriceps, you will also need isolating exercises such as leg extensions to optimally develop all regions of the muscle group ^[ x ] .
With isolation exercises you can train smaller muscle groups that receive just a little too little stimulation during compound exercises, or that simply lag behind the rest. The rear delts, for example, can be trained with row exercises, but for optimal development they often also need some isolating work, for example reverse machine flyes. And although you also train the biceps with rows in addition to the back , you will need isolation exercises such as curls to optimally train the biceps.
Although compound exercises have the greatest RSM, the more/often you do them, the less favorable the Stimulus to Fatigue Ratio (SFR). This means that the unmistakably large stimulus is matched by an increasing fatigue: not only central fatigue and local fatigue (those in the muscle), but also stress on joints and tendons. If you are more advanced and need a lot of volume, for example 20 sets per muscle group per week, then you can’t get it exclusively from compound exercises. For chest, this means, for example, that you do the bench press and dips (compounds), supplemented with cable flyes (isolating).
With isolation exercises you can make a better mind-muscle connection than with compound exercises. For some muscles, such as biceps, delts and calves, isolation work is almost indispensable to really feel and stimulate the muscle. There is consistently more doubt about the importance of mind-muscle connection in compound exercises. It seems to be at the expense of your performance and therefore also of muscle growth.
Isolation exercises offer a solution when assisting muscles become fatigued before the target muscle. For example, a narrow bench press is a very effective exercise for the triceps, but not if your chest gives out before the triceps during a set. Then you actually mainly train your chest.
Isolation exercises offer a solution when you are injured and therefore have to spare certain muscles and/or train lighter.

CONCLUSION AND ADVICE

Are compound exercises important for muscle growth? Yes. Are they better than isolation exercises? Not necessarily. If you had to choose between the two, compound exercises would win as they work the most muscle groups at once and produce the greatest stimulus. Fortunately, you don’t have to choose.

In practice, a combination of compounds and isolation exercises for muscle growth works best. After all, it is about the mechanical tension that you exert on a muscle group and that is not exclusively linked to one type of exercise. Most muscles are best trained through a combination of compound and isolation exercises.

This can also be deduced from Schoenfeld’s meta-analysis. Coach Menno Henselmans about this study:

What determines how well an exercise stimulates muscle growth is primarily how much mechanical tension it imposes on the muscle and over which lengths. Whether this tension is created by a compound or an isolation exercise, a kettlebell or a barbell, or if it involves one or more joints, those things don’t inherently matter. ^[ xv ]

And Schoenfeld himself:

Program design should focus on integrating applied anatomical theory that takes into account each muscle’s unique composition and function. ^[ xiv ]

If you don’t have much time, you get the most return from compound exercises. You train multiple muscle groups at the same time and they cause the largest Raw Stimulus Magnitude.

PROGRAMMING

Compound exercises can and should be performed heavily, so in the range of 5 to 10 reps. ‘Must’, otherwise you’ll miss out on this particular benefit; you can’t do isolation exercises that hard. In addition, squatting in high rep ranges, for example, is simply killing. It just causes a lot of unnecessary central and mental fatigue.

When doing compound exercises, always observe 1-3 Reps In Reserve (RIR), in other words stay one to three repetitions away from muscle failure. Training compounds to muscle failure results in little or no extra muscle failure, but it does result in a disproportionate amount of extra fatigue. In addition, it increases the risk of injuries.

Isolation exercises become more important as you get more advanced and need more volume to grow. Although you can of course also do isolation exercises as a beginner. For optimal development of some muscle groups, such as biceps, calves and side delts, isolating exercises are even indispensable.

In isolation exercises you use lighter weights and therefore more repetitions. As a rule, aim for 10-20 reps. You may (or must) train closer to muscle failure, for example with 1 RIR and every now and then also to complete muscle failure (0 RIR), for example in the last set.

Keep the isolation work in proportion. Mike Israetel recommends completing about 2/3 to 75% of your training program with compound exercises and the rest with isolation exercises ^[ xii ] .

Last updated on May 16, 2022.

How important are compound exercises for muscle growth?