Muscle confusion is based on the idea that muscle growth is best achieved by “keeping your muscles guessing” and constantly switching things up.
Some workout routines recommend varying your exercises on a weekly basis, while others tell you to change things every day.
By continually mixing things up, your body is forced to respond. The plateaus you get with regular training programs are avoided entirely, putting you on the path to rapid muscle growth.
Or so the theory goes anyway.
Is it true that your muscles won’t continue to grow unless you keep them confused? Is muscle confusion really the best way to build muscle?
The History of Muscle Confusion
The term “muscle confusion” first became popular with programs like P90X, which promotes the idea that constantly changing your workouts will confuse your muscles and help you avoid plateaus.
Here’s a promotional video for P90X if you want to see what it’s all about:
However, the notion that more variety equals more results has been around for a lot longer than P90X. The first time I came across the idea was back in the 1980s, where muscle confusion was one of Joe Weider’s infamous Weider Training Principles.
Here’s how the Muscle Confusion Training Principle was described back in the 1988 edition of Joe Weider’s Bodybuilding System:
Part of constant growth is never allowing your body to fully adapt to one specific training routine. muscles should never accommodate. To grow they need stress. If you constantly vary exercises, sets, reps and angle of pull upon your muscles, they can never accommodate and adjust to the stress upon them. One of my strong beliefs is: To keep your muscles growing and changing, you must confuse them.”
Can Muscle Confusion Trick Your Muscles Into Growing?
Although muscle confusion has been talked about for decades, it’s only in recent years that researchers have put the idea to the test .
They rounded up a group of men, all of whom had been lifting weights for at least two years, and assigned them to one of two groups.
Both groups lifted weights four times a week, following an upper/lower split routine. They also did the same number of sets for each muscle group, with each set taken to volitional failure in the 6-12 rep range.
The key difference between the two groups was that the fixed exercise group performed the same exercises in the same order.
Group two, on the other hand, used a special iPhone app that made a random selection from a database of 80 possible exercises.
The randomization algorithm was written to select three pulling (e.g., pull-up, lat pulldown and pullover) and three pushing (e.g., bench press, standing military press and dumbbell flyes) exercises for the upper-body, with no exercise repeated within the same workout.
For the lower body, the algorithm chose three exercises with greater participation of the anterior chain (e.g. squat, leg extension and leg press) and three for the posterior chain (e.g. deadlift, hip thrust and leg curl).
After eight weeks, there was no statistically significant difference in muscle growth between the two groups. Randomly switching exercises from workout to workout delivered no additional gains in size or strength.
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In fact, when you dig deeper into the results, it was the fixed exercise group that saw the biggest gains.
Rectus femoris, one of the four muscles that make up the quadriceps, grew more than three times faster in the fixed exercise group. Gains in two of the other heads of the quadriceps were also roughly 50% greater in the fixed exercise group.
In other words, randomly changing exercises every workout isn’t going to accelerate your results. You’ll often do just as well sticking with the same routine from one week to the next.
Does Muscle Soreness Mean Muscle Growth?
One of the things you’ll notice when you start doing different exercises is feeling sore and stiff for a day or two after the workout.
You went to the gym yesterday. Today, your muscles feel sore. That must mean your workout was an effective one, and that growth is sure to follow.
On the flip side, if you’ve stopped feeling sore, you need to switch things up if you want to get your muscles growing again.
Or do you?
In fact, when high- and low-soreness training programs have been put to the test, both deliver similar gains in muscle mass .
While doing lots of different exercises might leave you feeling sore the next day, it won’t automatically “shock” a muscle into growth.
The fact your muscles feel sore after a workout doesn’t mean they’re going to grow any faster.
There’s very little evidence to show that muscle soreness is a reliable indicator of muscle damage, that being sore means faster muscle growth, or that a lack of soreness means that your workout wasn’t effective.
When you introduce a new exercise into your routine, you’ll tend to get stronger relatively quickly. But this isn’t because you’ve suddenly gained a lot of new muscle.
Instead, the reason people make rapid improvements in strength with a new exercise is that their nervous system gets better at recruiting muscle fibers. It’s not necessarily because the fibers themselves have got any bigger.
Challenge Rather Than Confuse Your Muscles
If you want a muscle to grow, you will need to increase the demands you impose on that muscle.
Do the same exercises, for the same number of sets and reps, while lifting the same amount of weight, for the next five years. Nothing much is going to happen.
For example, lifting 100 pounds for 4 sets of 5-8 reps might be enough to stimulate growth. But over time, your body will adapt to that particular stress and stop growing.
If you want your body to continue adapting and improving, you need to provide it with a challenge it hasn’t adapted to.
That stimulus can come in the form of pushing yourself to do an extra rep with the same amount of weight, the same number of reps with a little more weight on the bar, or an extra set of the same exercise. It doesn’t require changing your entire routine.
For example, let’s say that your current routine involves 3-4 sets of 8-12 repetitions of a particular exercise.
You start out doing 3 sets of 8 reps. Over time, you keep on adding reps until you’re able to do 3 sets of 12. Then, you add another set. As soon as you hit the point where you’re able to do 12 reps in that fourth set, you add weight, drop back to 3 sets of 8, and start the whole process all over again.
Doing 12 reps in all four sets serves as the trigger for adding weight. When you hit 12 reps, the weight goes up. If you can’t, carry on using the same weight until you do.
In other words, an effective training stimulus can involve nothing more complicated than striving to add sets and reps to an exercise, or more weight to the bar.
The Importance of Experimentation
Different people respond at different speeds to different doses and types of training. Some people do better with one routine, while others make their best gains with another.
And the only way to know what type of training works best for you is with some experimentation. That is, you pick one or two variables in your training program to adjust, and observe how making those adjustments affects your progress.
When you’re constantly changing this or altering that, randomly selecting a different workout from one day to the next, evaluating your progress is difficult.
With systematic experimentation, discarding the things that don’t work and keeping the things that do, you’ll eventually learn what type of training routine your body responds best to.
When you find a routine that’s working, stick with it, at least until you reach the point where you’re no longer making gains. Once you’ve established what works for you, why abandon it in favor of something that might not work as well?
How and When to Change Your Workout
None of this means you should stick to the same exercises all the time, and do nothing but add weight and reps.
In fact, one of the best ways to add variety to your training program without screwing up your progress is to use the same workout template and rotate some of the exercises on a semi-regular basis.
One of the big benefits to rotating exercises is a reduction in the risk of “repetitive stress” injuries. Doing the same exercises week after week, especially if you’re lifting heavy weights, can take a big toll on your joints.
Your wrists, elbows and shoulders feel constantly sore. The pain eventually gets so bad that it interferes with your training. You end up having to wait weeks, sometimes even months, before you can train properly again.
Most of the exercises you do can be put into one of these categories:
- Horizontal push (e.g. bench press)
- Horizontal pull (e.g. dumbbell row)
- Vertical pull (e.g. lat pulldown)
- Vertical push (e.g. overhead press)
- Squat (e.g. squat)
- Hip hinge (e.g. deadlift)
Rotating exercises involves taking an exercise from one category and replacing it with another exercise from the very same category.
You might start out using the seated row as your main horizontal pulling exercise. Then you can switch to dumbbell rows, inverted bodyweight rows or any horizontal rowing movement that provides a sufficient level of resistance.
With the deadlift, you might begin with a regular deadlift. Then you switch to a Romaniean deadlift. Then you replace the Romanian deadlift with rack pulls. Although you’re still doing a deadlift, each variation will shift the emphasis to a different set of muscles.
The same principle holds true with the other primary exercises. Dumbbells can take the place of barbells in both the bench press and overhead press. The leg press or trap bar deadlift can replace the squat.
For best results, there should be some kind of semi-regular variation in your selection of exercises. Many of the training programs used by members of the Westside Barbell club, which has produced some of the biggest, strongest men on the planet, involve rotating exercises on a weekly or biweekly basis.
This gives you the consistency of a structured plan but with enough variety to stop you getting bored.
Heavy, Medium and Light Training Days
The other day, I was reading about a guy who’d signed up for some personal training at a local gym.
He met with his trainer 3-4 times a week, and the workouts rotated between heavy, medium and light training days.
The trainer told him that switching up the weights and reps kept his muscles from getting used to the workouts, which could cause a plateau. By “confusing” his muscles, the gains would be steadier and more consistent.
While muscles don’t get confused, that doesn’t mean there are no benefits to having heavy, medium and light training days. Sometimes, a particular training method can work, just not for the reasons some people think it works.
Changing your weight and reps from workout to workout, for example, has been shown (in some studies at least) to have a small but beneficial effect on muscle growth.
In one trial, a group of trained men lifted weights three times a week using either a constant or varied training program .
The constant group kept their training program the same, doing 8-12 reps on every set. The varied group changed both the weight and the number of reps, switching from heavy (2-4 reps) to medium (8-12 reps) to light (20-30 reps) on days one, two and three, respectively.
While both groups gained muscle and got stronger, it was the varied group that saw the best results. But this had nothing to do with muscle confusion. Rather, it was because training with higher reps appears to stimulate more growth in the slow-twitch muscle fibers 
None of this means you can’t get in better shape with workout routines like P90X. If you want to lose some fat, gain a little muscle and get a bit fitter, they’re a lot better than doing nothing.
But muscle confusion isn’t the reason they work.
Your muscles don’t get confused. They adapt to various types of “stress” in such a way that they’re better able to handle that same source of “stress” in future.
Focus on challenging – rather than confusing – your muscles. They’ll respond by growing bigger and stronger in response to that challenge.
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