You just finished a solid 12-week squat cycle. Your 1-rep max is through the roof. But if I asked you to perform a max-effort isometric hold at your sticking point, would that number be up too?
According to a massive new systematic review and meta-analysis, the answer is: probably not as much as you'd think. This research dives deep into one of the oldest principles in the book—task specificity—and confirms that strength is not just one thing. How you build it and how you measure it matters immensely.
Let's break down what the science says and what it means for how you train and track your progress.
The Main Finding: Specificity Is King
Researchers pooled the data from 43 different studies to see how traditional dynamic resistance training (think squats, bench presses, curls) impacts two different types of strength:
- Dynamic Strength: The ability to move a weight through a range of motion (e.g., your 1RM).
- Isometric Strength: The ability to produce force against an immovable object (e.g., pushing against a fixed pin in a rack).
The results were crystal clear. Dynamic training produced moderate-sized improvements in dynamic strength (Standardized Mean Difference, SMD = 0.98). This is what we'd expect—you train the lift, you get better at the lift.
However, the transfer of those gains to non-trained isometric tests was only small (SMD = 0.42). In simple terms, the strength gains seen in the actual trained lifts were more than double the gains seen in isometric tests of the same muscles.
This confirms the principle of specificity: the adaptations to training are highly specific to the task you perform. Getting strong at moving a weight is a different skill than getting strong at holding a weight still.
Why the Big Difference? It's Not Just About Muscle Size
The researchers investigated potential reasons for this gap. They looked at whether gains in muscle size (hypertrophy) or changes in muscle activation could explain the difference. Surprisingly, neither could predict the changes in dynamic or isometric strength.
So, if it's not just bigger muscles, what is it?
The study suggests the answer lies in neural adaptations. Dynamic, multi-joint lifts like a squat require immense coordination, stability, and technical skill. Your nervous system learns to fire the right muscles in the right sequence at the right time to complete the lift. This is a skill that doesn't fully transfer to a static, isometric contraction, which has much lower coordination demands.
Since most of the studies analyzed were 12 weeks or shorter, these neural, skill-based adaptations likely played a dominant role in the strength gains.
Does Training Status Change Anything?
Coaches often wonder if these principles apply differently to beginners versus advanced lifters. The meta-analysis broke down the results by training status:
- Sedentary/Untrained: Saw the largest gains in both dynamic (SMD = 1.27) and isometric (SMD = 0.58) strength.
- Resistance Trained: Saw the smallest gains (SMD = 0.75 dynamic, SMD = 0.29 isometric), likely due to being closer to their genetic ceiling.
But here's the key takeaway: while the absolute numbers changed, the ratio didn't. Across all experience levels, the dynamic strength gains were 2.2 to 2.6 times greater than the isometric strength gains. The principle of specificity holds true whether you're a newbie or a seasoned vet.
A Quick Look at Single-Joint vs. Multi-Joint Lifts
Interestingly, the type of exercise seemed to matter for strength transfer. While both multi-joint (e.g., squats) and single-joint (e.g., leg extensions) exercises showed strong specific gains, single-joint exercises had a better carryover to isometric strength.
The transfer effect for single-joint exercises was moderate (SMD = 0.70), while for multi-joint exercises it was small (SMD = 0.33).
The authors propose a few reasons for this. Multi-joint lifts are more complex, and synergist or stabilizer muscles might fatigue before the prime movers get an optimal stimulus. In contrast, a single-joint exercise isolates a muscle group more effectively, which may lead to adaptations that transfer better to a simple isometric test of that same muscle.
What This Means For Your Training and Testing
This isn't just academic—it has direct, practical implications for every lifter and coach.
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Train for Your Goal: If your goal is to increase your 1RM in the squat, bench, and deadlift, the vast majority of your training should be focused on dynamic lifting. Specificity dictates that this is the most direct path to your goal.
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Test How You Train: Using an isometric test to gauge the success of a dynamic training program can be misleading. It might significantly underestimate your actual strength gains. If you're training for a better 1RM, your primary test should be a 1RM (or a 3RM/5RM test).
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Recognize That Strength is Multi-Faceted: Dynamic and isometric strength are different qualities. The study found almost no predictable relationship between the changes in the two. Think of them as separate domains. Improving one doesn't guarantee a proportional improvement in the other.
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Use Isometrics Strategically: This doesn't mean isometric training or testing is useless. Isometrics are incredibly valuable for rehabilitation, improving force production at specific joint angles (like a sticking point), and are generally safer and less fatiguing than maximal dynamic testing. Just understand what they are—and aren't—measuring.
The Bottom Line
This robust meta-analysis reinforces a foundational training principle: you get good at what you do. Dynamic resistance training is fantastic for improving your ability to lift heavy weights through a full range of motion. However, those gains are highly specific and don't transfer completely to other expressions of strength, like isometric force.
So, keep your training and testing aligned. If you want to lift more, lift. And measure your progress by, well, lifting.
Reference:
Saeterbakken, A. H., Stien, N., Paulsen, G., Behm, D. G., Andersen, V., Solstad, T. E. J., & Prieske, O. (2025). Task Specificity of Dynamic Resistance Training and Its Transferability to Non-trained Isometric Muscle Strength: A Systematic Review with Meta-analysis. Sports Medicine (Auckland, N.z.). Advance online publication. https://pubmed.ncbi.nlm.nih.gov/40314751/