You see it all the time in the gym: one person lowering the bar with painstaking control, another performing reps with a more explosive tempo. The debate over rep speed, especially the eccentric (lowering) phase, has been around for decades.
Should you be counting seconds on the way down to maximize your gains? Or is a faster, more natural tempo better?
Fortunately, a brand new systematic review and meta-analysis from the Journal of Sports Sciences gives us the most up-to-date answer. Researchers Amdi and King pooled the data from nine different studies to see how eccentric duration impacts strength, muscle growth, and athletic performance.
Quick note: This review is based on the study's abstract, as the full text is not publicly available. We're working with the highest-level summary provided by the researchers.
The Study: Shorter vs. Longer Eccentrics
The researchers compared two main conditions:
- Shorter Eccentric Group (SEG): Lifters using a faster lowering phase.
- Longer Eccentric Group (LEG): Lifters using a slower, more prolonged lowering phase.
They analyzed the effects on three key outcomes: maximal strength, muscle hypertrophy (size), and countermovement jump (CMJ) height, a common measure of explosive power. The analysis included 166 participants, with nearly half being classified as 'trained'.
So, what did they find?
For Power and Athleticism: Faster is Better
When it comes to improving your ability to jump, sprint, and be explosive, the verdict is clear.
The meta-analysis found that the shorter eccentric group (SEG) saw significantly better improvements in countermovement jump height. The researchers described this enhancement as being of a "practically worthwhile degree" and had "moderate certainty" in this finding.
The Coach's Takeaway: If you're an athlete whose sport demands explosive power, a faster, more natural eccentric tempo is likely superior. This aligns with the principle of specificity—to be fast, you need to train fast. Deliberately slowing down the eccentric phase may blunt your explosive potential.
For Muscle Hypertrophy: It's a Wash
This one might surprise the "time under tension" purists. When comparing shorter versus longer eccentrics for building muscle, the researchers found "uncertain estimates."
In simple terms, there was no clear winner. The data did not show a meaningful advantage for either slow or fast eccentrics when the goal was purely muscle growth.
The Coach's Takeaway: Don't overthink your eccentric speed for hypertrophy. As long as you are controlling the weight and not just dropping it, the exact duration of the negative probably matters less than other variables like mechanical tension, training volume, and effort. Pick a controlled tempo that allows you to feel the target muscle working and stick with it.
For Maximal Strength: The Answer is Nuanced
Here's where things get interesting. Overall, the analysis for maximal strength was also uncertain. However, the researchers dug deeper with subgroup analyses, which revealed two key scenarios where a longer eccentric might be better.
Longer eccentrics (LEG) led to similar or even enhanced strength gains compared to shorter eccentrics under two specific conditions:
- In trained participants: Experienced lifters seemed to benefit more from a slower negative.
- When volume-load was matched: In studies that ensured both groups performed the same total amount of work, the slower eccentric group had a slight edge.
The researchers reported these findings with "moderate certainty."
The Coach's Takeaway: If you're a beginner, the difference is likely negligible. But if you're an intermediate or advanced lifter, deliberately slowing down your eccentrics could provide a small but meaningful boost to your strength gains. This could be due to improved technique, greater motor unit recruitment, or increased stress on the muscle fibers that drives strength adaptation.
Your Action Plan Based on the Science
So, how fast should you lower the bar? The classic coach's answer applies: it depends on your goal.
- If your primary goal is POWER: Use a faster, more explosive eccentric tempo.
- If your primary goal is HYPERTROPHY: It doesn't seem to matter much. Focus on control, not a specific second count.
- If your primary goal is STRENGTH (and you're a trained lifter): You may get a slight edge by using a longer, more controlled eccentric.
This study provides a fantastic, evidence-based framework for programming tempo. It moves us away from dogmatic rules and toward a more goal-oriented approach. As always, more research is needed to confirm these findings, but for now, you have a solid guide for your next training block.
Reference:
Amdi, C. H., & King, A. (2025). The effect of eccentric phase duration on maximal strength, muscle hypertrophy and countermovement jump height: A systematic review and meta-analysis. Journal of sports sciences. https://pubmed.ncbi.nlm.nih.gov/40692176/