Do you religiously swap your exercises every few weeks to 'confuse' your muscles? Or are you a creature of habit, sticking to the same bread-and-butter lifts day in and day out? The debate between consistency and variation is a classic in the gym. Proponents of variation claim it’s key to sparking new growth, while fans of consistency argue that mastering a few key lifts is the fastest path to progress.
A new study published in Research quarterly for exercise and sport decided to put this question to the test, directly comparing a constant exercise routine to a systematically varied one. Let's break down what they did and what it means for your training.
A quick note: This analysis is based on the study's abstract, as the full text was not available for review.
The Study: Constant vs. Varied Routines
Researchers took 70 young women and randomly split them into two groups for a 10-week training program. Both groups trained their lower body three times per week, performing two sets of 10-15 repetitions to failure on each exercise. The only difference was the exercise selection.
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The Constant Group (CON-RE): This group performed the 45º leg press and stiff-leg deadlift in every single training session for 10 weeks.
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The Varied Group (VAR-RE): This group rotated through different, but similar, exercises each session of the week:
- Day 1: 45º leg press & stiff-leg deadlift
- Day 2: Hack squat & prone leg curl
- Day 3: Smith machine squat & seated-leg curl
Before and after the 10 weeks, the researchers measured muscle thickness in the quads, hamstrings, and adductors using ultrasound to assess hypertrophy. They also tested strength using a one-repetition max (1RM) on the 45º leg press (a trained exercise) and the leg extension (an untrained exercise).
The Results: A Surprising Tie
After 10 weeks of consistent training, the researchers compared the gains between the two groups. Here’s what they found.
Muscle Growth (Hypertrophy)
Both groups packed on a significant amount of muscle, and there was no meaningful difference between them. Thigh muscle thickness increased similarly across the board.
- Constant Group: +7.8% to +17.7% increase in muscle thickness.
- Varied Group: +7.5% to +19.3% increase in muscle thickness.
Switching up the exercises didn't lead to more growth. Sticking to the same two lifts proved just as effective.
Strength Gains
Just like with hypertrophy, the strength results were virtually identical. Both groups saw impressive increases in their 1RM on both the trained leg press and the untrained leg extension.
- Constant Group: +24.4% to +32.1% increase in 1RM strength.
- Varied Group: +29.0% to +30.1% increase in 1RM strength.
The idea that variation is necessary to maximize strength didn't hold up here. Both strategies worked equally well.
What This Means For Your Training
The study's conclusion is clear: both constant and varied resistance training routines resulted in similar gains in muscle strength and hypertrophy. So, what are the practical takeaways for you as a lifter or coach?
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'Muscle Confusion' Isn't a Magic Bullet: This study suggests that the need to constantly change exercises to 'shock' the muscle is likely overstated, at least within a 10-week timeframe. The real drivers of progress are consistent effort and progressive overload—adding weight, reps, or sets over time.
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Consistency Is a Perfectly Valid Strategy: If you have a set of core compound lifts that you enjoy and can progress on, there's no need to feel pressured to change them. Mastering the technique and getting stronger at a handful of key exercises is a time-tested way to build muscle and strength.
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Structured Variation Is Also a Great Option: This study didn't show that variation is bad—it just showed it wasn't superior. If you get bored easily, have nagging aches from certain lifts, or just enjoy variety, a well-designed program that rotates similar movement patterns is an equally effective choice. The varied group in this study used a smart, structured approach, not random 'workout of the day' chaos.
Ultimately, the best program is the one you can stick to consistently and work hard on. This research empowers you to choose the strategy that best fits your psychology, goals, and equipment access. Whether you stick to the basics or rotate your lifts, the key is to show up, train hard, and focus on long-term progression.
Reference:
Kassiano, W., Costa, B., Kunevaliki, G., Nunes, J. P., Castro-E-Souza, P., de Paula Felipe, J., Tricoli, I., Luiz, A., Tricoli, V., & Cyrino, E. S. (2025). Muscle Hypertrophy and Strength Adaptations to Systematically Varying Resistance Exercises. Research quarterly for exercise and sport. Advance online publication. https://pubmed.ncbi.nlm.nih.gov/39388663/