Exercise Variety: The Spice of Life at the Gym
I have been lifting for 40 years, and I almost never do the same workout twice. That sounds like a confession that I fell for "muscle confusion," the idea that you have to keep your muscles guessing or they will get bored and stop growing, but it is not. Muscles do not get bored, and they are not confused by anything. Muscles are stupid. The real question is whether exercise variety helps you build muscle and strength, or whether you are just going throught the motions. There is a difference between training and working out. The former entails a systematic approach incorporating progressive overlead whereas the latter is work willy nilly with no plan.
The honest answer is that exercise variety works when it has a reason behind it and does nothing, or slightly less than nothing, when it is random. The research on this has gotten good enough over the last few years that we can actually say which kind of variety earns its place in your program and which kind is just noise.
Where Muscle Confusion Came From
Joe Weider was selling the "Muscle Confusion Principle" to bodybuilders decades before P90X branded the phrase in the 2000s and put it on late night infomercials. Some writers, including a 2020 New York Times piece, credit P90X with inventing the term, but the infomercial crowd only repackaged an old bodybuilding idea with better lighting and enhanced before anbd after shots. The pitch was always the same: change your workout constantly, keep the body off balance, and you will avoid the dreaded plateau.
The concept has stretched so far that it now means almost anything. One recent outdoor magazine article redefined muscle confusion as adding sprints or Japanese interval walking to your week, which is a perfectly good idea that has nothing to do with the original claim and everything to do with doing some conditioning. When a term can mean "rotate your curls" and "go walk briskly for three minutes" at the same time, it has stopped meaning anything at all. This is not a postmodernist workout.
What the Exercise Variety Studies Actually Show
The cleanest test of pure muscle confusion came in 2019, when researchers gave one group of trained men a fixed program and had the other group use a phone app that randomly picked their exercises every session. After eight weeks, strength and quad thickness improved about the same in both groups, and if anything the fixed group's quads trended slightly ahead. The one clear difference was motivation, which went up in the random group and drifted down in the group repeating the same routine.
A larger 2024 trial in 70 untrained women found the same thing: rotating leg exercises session to session produced muscle growth of roughly 8% to 19% across thigh sites, which was virtually identical to the group that did leg press and stiff leg deadlifts every single time. Strength gains were also a wash. So if you were hoping that constant novelty unlocks secret gains, the data says sorry, not sorry.
Here is where it gets more interesting. A 2022 systematic review by Kassiano, Schoenfeld and colleagues pooled the available studies and concluded that some systematic exercise variety appears to improve regional muscle growth and strength, while excessive random rotation may actually hurt your results. In plain English, swapping exercises for a reason helps, and swapping exercises because you are bored of your playlist does not.
Why Some Muscles Need More Than the Big Lifts
The reason variety matters at all comes down to anatomy. Some muscles cross two joints, and the big compound lifts can leave them underworked because one of the joint actions in the lift works against them. The rectus femoris (big thigh muscle) is the classic example, since it extends the knee but also flexes the hip, and the hip is extending hard during a squat or leg press.
A 2024 study from Brad Schoenfeld's lab at Lehman College trained each leg of the same person differently for eight weeks. The leg extension grew the rectus femoris more, while the leg press grew the vastus lateralis more, which means doing both beats doing either one alone. That lines up with an earlier squat study in which ten weeks of squatting grew the quads, glutes and adductors but left the rectus femoris and the hamstrings essentially unchanged.
The triceps follow the same rule. The long head crosses the shoulder, so pressing does not train it well, and overhead triceps extensions produced roughly 40% more total triceps growth than pushdowns in a 12 week trial. I made a similar argument in There Are No Bad Exercises: exercises are tools, and the question is always what job you are hiring them to do.
When Exercise Variety Is a Waste of Time
Calves are where the variety argument falls apart. Bodybuilders have insisted for decades that you need seated calf raises to hit the soleus, because bending the knee takes the gastrocnemius out of the picture. It sounds smart and the data does not care. Despite this, I still train my skinny calves seated and in the standing postion.
In a 2023 trial using MRI, standing calf raises grew the lateral gastrocnemius by 12.4% versus 1.7% for seated raises, and the medial gastrocnemius by 9.2% versus 0.6%, while the soleus grew about the same with either version. The Lehman study found the same pattern, with straight leg calf raises winning for the medial gastrocnemius and the soleus barely moving either way. So your time on the seated calf machine is probably better spent on the standing version, which is a sentence I never expected to type with this much confidence.
The lesson is not that variety is good or bad. The lesson is that variety should follow anatomy, and when one exercise already covers every function of a muscle, adding a second one is just extra laundry.
What About Changing Reps Instead of Exercises?
There is another flavor of variety that people confuse with muscle confusion: changing your rep ranges from day to day while keeping the exercises mostly the same. This is called daily undulating periodization. The famous 2002 study by Rhea and colleagues found that daily changes roughly doubled strength gains compared to changing every four weeks.
That result made a lot of noise, but it has not held up as a rule. Later meta analyses found no meaningful difference in strength between undulating and linear plans, and no difference in muscle growth either. Undulating your reps is a perfectly good way to train, just not a magic one, and it is fine if your heavy day, moderate day and pump day are chosen by what you feel like doing. I call this instinctual training.
Motivation and Injury: The Case I Can Make and the One I Can't
The strongest evidence based argument for exercise variety is not physiological at all. It is that you keep showing up, and the 2019 random exercise study is the best data we have on that, with motivation climbing in the group that kept things fresh. Schoenfeld, who coauthored it, has said that a middle ground of swapping one or two exercises at a time is probably the sensible approach.
That matches my own experience. I once ran a program for six months with the exact same exercises every session, and I never felt worse in the gym or less motivated to get there. That is a sample size of one, but after 40 years of training I trust it more than a fitness influencer's sample size of zero.
I also believe that hitting joints from different angles helps keep repetitive wear patterns from developing, and I want to be honest that I cannot point to a study proving it. Strength training as a whole cuts injury risk in a dose dependent way, and overuse is a known driver of gym injuries, but nobody has run a trial showing that rotating your rows prevents a cranky shoulder. If you already have one, my post on shoulder pain myths and realities is a better place to start than a new row variation.
How I Actually Use Exercise Variety
Here is the system I use, and it happens to be where the research lands too. I keep track of about 15 core exercises, and I make sure each one shows up at least once a week or once every two weeks, with progress tracked on every one of them. I deadlift once a week, train legs twice a week, and do pull ups at least once a week no matter what else happens.
Everything around those anchors rotates. One day the row is a machine row, the next it is a standing band row, and the pressing angle, grip and stance change regularly. The anchors give me something to progress and measure, which is the non negotiable rule of building muscle, and the rotation keeps boredom away and covers the muscles the big lifts miss.
Exercise selection is largely a matter of preference once you are training hard, pushing close to failure, getting enough weekly sets and choosing movements that load the muscle through a deep stretch. Variety is the seasoning, not the meal.
Bottom Line
Exercise variety is the spice of life at the gym, but spice is not a food group. Random rotation does not build more muscle than a well chosen fixed training program, though it may keep you more motivated. Smart variety, chosen to cover muscles that the compound lifts miss, does build more complete muscle, and constant change for its own sake can make progress harder to track.
Practical Tips
Pick a short list of core lifts and progress them on purpose, whether you track weight, reps or sets.
Add single joint work for muscles that cross two joints, such as leg extensions for the rectus femoris, leg curls for the hamstrings and overhead extensions for the triceps.
Rotate accessory movements, angles and grips to stay engaged, but swap one or two at a time rather than rebuilding the whole program every session.
If you are dreading the gym, change something. A program you skip has an effect size of zero.
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References
Baz-Valle E, Schoenfeld BJ, Torres-Unda J, Santos-Concejero J, Balsalobre-Fernández C. The effects of exercise variation in muscle thickness, maximal strength and motivation in resistance trained men. PLoS One. 2019;14(12):e0226989.
Kassiano W, Costa B, Kunevaliki G, et al. Muscle hypertrophy and strength adaptations to systematically varying resistance exercises. Res Q Exerc Sport. 2024.
Kassiano W, Nunes JP, Costa B, Ribeiro AS, Schoenfeld BJ, Cyrino ES. Does varying resistance exercises promote superior muscle hypertrophy and strength gains? A systematic review. J Strength Cond Res. 2022;36(6):1753-1762.
Burke R, Piñero A, Mohan AE, et al. Exercise selection differentially influences lower body regional muscle development. J Sci Sport Exerc. 2024.
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Maeo S, Wu Y, Huang M, et al. Triceps brachii hypertrophy is substantially greater after elbow extension training performed in the overhead versus neutral arm position. Eur J Sport Sci. 2023.
Kinoshita M, Maeo S, Kobayashi Y, et al. Triceps surae muscle hypertrophy is greater after standing versus seated calf-raise training. Front Physiol. 2023;14:1272106.
Rhea MR, Ball SD, Phillips WT, Burkett LN. A comparison of linear and daily undulating periodized programs with equated volume and intensity for strength. J Strength Cond Res. 2002;16(2):250-255.
Harries SK, Lubans DR, Callister R. Systematic review and meta-analysis of linear and undulating periodized resistance training programs on muscular strength. J Strength Cond Res. 2015;29(4):1113-1125.
Grgic J, Mikulic P, Podnar H, Pedisic Z. Effects of linear and daily undulating periodized resistance training programs on measures of muscle hypertrophy: a systematic review and meta-analysis. PeerJ. 2017;5:e3695.
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Doug Joachim - NYC / www.JoachimsTraining.com
