New Meta-Analysis Settles the Debate on Negatives vs Positives for Muscle Growth
A 26-study meta-analysis reveals whether lowering or lifting the weight matters more for building muscle.
Summary
A major new meta-analysis of 26 studies and over 600 subjects examined whether the negative (lowering) or positive (lifting) phase of an exercise drives more muscle growth. Results showed that for upper body muscles, emphasizing the negative phase produced a small but statistically significant advantage in hypertrophy. For lower body muscles, both phases produced similar growth. Overall, across the whole body, the two phases were roughly equivalent. The practical takeaway is to control your negatives — especially for upper body work — but the popular belief that negatives are dramatically superior to positives for muscle growth is not strongly supported by the current evidence. Both phases contribute meaningfully to gains.
Detailed Summary
Muscle hypertrophy is a cornerstone of healthy aging, with greater muscle mass linked to reduced mortality, better metabolic health, and improved functional longevity. Understanding which aspects of resistance training most efficiently drive muscle growth helps health-conscious individuals train smarter and get more return from their time investment in the gym.
This video by Jeff Nippard breaks down a brand-new meta-analysis by da Silva et al. (2025), which pooled data from 26 studies and over 600 subjects to compare muscle growth outcomes when emphasizing the concentric (positive, lifting) phase versus the eccentric (negative, lowering) phase of resistance exercise. The eccentric phase has long been theorized to be superior because muscles are under load while lengthening, generating greater mechanical tension — a primary driver of hypertrophy signaling.
The findings were nuanced. For upper body muscles, there was a small but statistically significant advantage favoring the eccentric-emphasized approach, suggesting that controlling the negative does offer a measurable edge in arms, chest, back, and shoulders. However, for lower body muscles — quads, hamstrings, glutes — both phases produced comparable growth. When results were combined across all muscle groups, the overall difference between emphasizing positives versus negatives was not dramatic.
For anyone training to preserve or build muscle as they age, the practical implication is clear: deliberately controlling the lowering phase of your lifts is worthwhile, particularly for upper body exercises. However, completely neglecting explosive or forceful concentric effort is unnecessary. Both phases of the lift contribute to meaningful hypertrophic stimulus.
This finding also challenges the often-repeated gym wisdom that negatives are drastically more important than positives. The science suggests a more balanced approach, where both phases are performed with intention, is likely optimal for long-term muscle health and longevity-relevant outcomes.
Key Findings
- Eccentric (negative) phase produces a small but significant upper body muscle growth advantage over concentric alone.
- For lower body muscles, emphasizing negatives versus positives yields similar hypertrophy outcomes.
- Overall across all muscle groups, both training phases build comparable amounts of muscle.
- Controlling the negative is still recommended, especially for upper body lifts, for marginal gains.
- The belief that negatives are dramatically superior to positives is not strongly supported by current evidence.
Methodology
Jeff Nippard is a well-regarded science-based fitness communicator with a strong track record of accurately translating peer-reviewed research. This video references a specific 2025 meta-analysis (da Silva et al.) covering 26 studies and 600+ subjects, lending it strong evidentiary grounding. The format appears to be a research breakdown explainer typical of Nippard's channel.
Study Limitations
This summary is based on the video description only, as no transcript was available — specific data points, effect sizes, and caveats from the full video may not be captured here. The meta-analysis referenced (da Silva et al., 2025) should be consulted directly to assess study quality, population characteristics, and heterogeneity. Individual variation in response to eccentric versus concentric training may differ based on training history, age, and muscle group.
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