“I always always always shock my body with new exercises.”
“I love it when my muscles are sore, because it means I worked hard.”

Stop the Confusion
I hear some version of those two statements often. Usually it’s people excitedly telling me about their new workout routine. When I see people that say this 3 months later, they usually are not working out anymore, and do not look any different than they did 3 months prior.

When I hear either or both of those statements, I try to encourage the person’s enthusiasm for their workout while also trying to convince them that there is a better way. It is tough though. I try to explain that constant muscle soreness is actually a sign of a poorly designed program. If you think about it, it makes sense that people don’t tend to stick to these workouts. At some point, you have to get sick of being sore every day!

When starting out a new program, even a good one, there is a chance that you will experience some soreness for a couple of days. This is called delayed onset muscle soreness, or DOMS, and is your body’s response to the new stresses it is enduring. In a good program, you will only get the soreness after a couple of workouts, and from then on, you will feel good, not sore, the day after you workout.

Why is regular DOMS a bad thing? Well for starters, the soreness tends to prevent you from moving for several days after that work out. It can also make you apprehensive about working out again – you may like the idea of feeling like they’ve worked hard, but muscles that hurt with every step are not fun. If you do make it to the workout, you won’t be able to exert yourself to your potential because your body is not up to it. Sore muscles do not perform as well as refreshed muscles, possibly even resulting in early fatigue leading to overuse injuries.

One of the causes of constantly sore muscles is always shocking your body with new exercises. This is because your body is constantly in adaptation mode: basically it is always on the defensive. Most of us have seen or heard of “muscle confusion theory”, which is one of the key features of programs like P90X and Insanity.

It is more marketing than science, and is loosely based on adaptation theory, which says that your body adapts to movements and eventually slows or even stops progress from doing the same movement.

It is important to acknowledge adaptation theory when doing exercise, but here’s the key problem with P90X, insanity, and any workout that involves always shocking your body with new exercises: It takes time for your body to adapt, and it is during that adaptation period that you improve. If you are always shocking your body, then you are not allowing your body to get stronger.

Training by always shocking your body with new exercises is akin to learning music by taking piano on Monday, clarinet on Wednesday and violin on Friday, followed by drums, trombone, and guitar the following week. At the end of two weeks you have tried 6 instruments, but can you do anything with any of them?

When you start a new exercise, the first couple of days you tend to lift lighter weights and move with a bit more apprehension. But as you get the hang of it after doing it a couple of times, you start to see big improvements from one day to the next, and you can continue to see this improvement for several weeks at least. This is when you get truly strong and fit. And this is what you rob yourself of when you apply muscle confusion theory in the popular modern context. Instead of giving yourself a few weeks or months to really get good at an exercise, you do it once and move on to another. Do you actually get anything out of it? Other than muscle soreness?

I am not suggesting that you continue to do the same workout forever. Your body will adapt to what you are doing eventually. Beginners can actually go for quite a long time before this happens. In fact for beginners, boredom will likely set in before adaptation. Boredom is a valid issue! If you get bored, then you will be less likely to continue to workout. So you should change up your workouts; just don’t do it quite so often! This is where using periodization come in. 

Periodization in training refers to the changes you make to your training plan over a period of time. For most people, changing some elements of their training every 3 to 6 weeks is optimal. It affords enough time for your body to really benefit from the exercise you are doing, but provides you with something new often enough that you don’t get bored. If you are not someone who bores easily, then you can keep the same exercises but change how many sets and repetitions you do; or change some but not all of the exercises.

If you are a competitive athlete, the periodization should be designed around your competition schedule, with a different focus for pre-season, in-season, and off-season.

Instead of confusing your muscles, give them a bit of time to learn how to be strong. Your body will thank you. 

Elsbeth Vaino is an FMS certified personal trainer in Ottawa, Canada.



  1. After the first week of doing P90X, I never felt sore at all. Your body adapts to the program. So in the beginning, you will definitely be sore because your body isn’t use to doing these exercises so yes it will be “confused”. But only for a certain period your body will be sore the next day.

  2. Thanks for the reply:) I see where you’re coming from much better, now. I think you phrased it perfectly when you said “The issue I have with commercial applications of muscle confusion is that the confusion is the plan versus being a piece of the plan.” I can’t agree more!

  3. Oops – saw your other comment first. But I agree with what you’ve said here. Although I might argue that what you describe is not muscle confusion in the commercial sense. I would suggest that what you’ve described is a well-thought out periodization plan that happens to include a (or some) phase(s) of variation, with a very important note that this is not an appropriate approach for beginners. The issue I have with commercial applications of muscle confusion is that the confusion is the plan versus being a piece of the plan. In fact even with my music analogy – once you have mastered several musical instruments, there is probably significant benefit to spending a period of time switching up the instrument you play. Much like there is carry over benefit from playing one sport to performance in another.

  4. Absolutely, and great points James. And yes – Ottawa is awesome. It’s a particularly nice April!

  5. Would just like to add one more thing. Undulating periodization(muscle confusion) can be combined with traditional, linear periodization. One part of your year, you can use the method for endurance, another part of the year for strength, etc. For fitness enthusiasts, you can do so when you want a new challenge or change. Doing this provides the benefits of both while taking a more holistic approach to your fitness.
    Elsbeth, speaking as a fellow resident, Ottawa rocks!

  6. You raise some good points but there is actually a ton of science supporting “muscle confusion”; after all, what it really is undulating periodization. Now, I’m not aware of the particulars of the P90x program but I do know what tends to be problematic with the implementation of muscle confusion: A) It should not be a beginner strategy- this a time of skill acquisition and for hardwiring the nervous system B) Not all variables should be changed at once- simply cycle between heavy, lower rep workouts and lighter, higher rep workouts to give higher threshold motor units a rest and also develop slower twitch muscle fibers through sufficient time under tension- they’re recruited but not taxed enough during heavier training. Any program- regardless of goal -can retain its focus(and thus ensure continuity)with this method simply by manipulating reps, etc. in the right zone according to desired adaptations on the repetition continuum. Examples: Hypertrophy- Heavy day, 6-10 reps per set. Light day, 10-15 reps. Endurance- Heavy day, 10-15 reps, Light day, 15-20. These are basic examples but you get the point. And, of course, there’s “spillover” from one adaptation to another- hence the term continuum. So don’t stop confusing your muscles! Just know how to go about it based on what you want.

  7. To each their own! You must of failed at p90x, cried and then felt obligated to write an article! Bring it!

  8. Another great article. I actually tried the P90x program two years ago just to see what it was all about. I followed it for 4 weeks straight and I found I lost muscle mass, lost functional movement and felt crappy. I had a few baseball players do the p90x program for the full 90 days and came out looking “ripped”. But lost a lot of functional movement creating weaker swings at the plate and lower throwing speeds. They too got rid of the dvd and went back to the program designed specifically for them. They said I have a great looking body but now I’m back to being an average player.

  9. Some definitely do, but I would suggest they would do even better – particularly in building strength – if they followed a program that involved proper progressions. And that would also lead to fewer P90x’ers dropping out due to injury.

  10. howcome the p90x graduates have such great results if what your saying is true?

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