New Study Reveals the Best Exercise for Muscle Growth – And It’s Not What You Think

A surprising new study from the International Institute of Strength & Performance (IISP) has just revealed shocking results about muscle growth – and gym bros everywhere are arguing.

Researchers compared two groups of lifters over a 12-week period:

• Group A: Focused on heavy weightlifting (5–6 reps, compound lifts)

• Group B: Used moderate weights with slower reps and longer time under tension (TUT)

Both groups followed identical diets and sleep schedules. But the results? 😲

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📊 Study Summary:

Participants: 40 male & female lifters, ages 21–38
Duration: 12 weeks
Controlled diet: 1g protein/lb of body weight
Training: 4x a week, split routines

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🔍 The Results:

Group A (Heavy Lifters):

• Strength gain: ↑ 22%

• Muscle size (hypertrophy): ↑ 9%

• Endurance: ↑ 6%

Group B (Slow TUT Lifters):

• Strength gain: ↑ 13%

• Muscle size (hypertrophy): ↑ 16%

• Endurance: ↑ 11%

  
  
  

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🧠 The Big Takeaway:

Contrary to what most gym-goers believe, the study showed that muscles grow better from longer tension than from simply lifting the heaviest weight possible.

In simple terms:
💡 It’s not how heavy you lift – it’s how long your muscles are working.

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🧪 What Is “Time Under Tension”?

TUT refers to the total amount of time a muscle is actively contracting during an exercise. Slowing down your reps (e.g., 4 seconds up, 4 seconds down) creates more tension, which triggers more muscle fiber damage — and more growth.

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🏆 Final Verdict:

If your goal is maximum muscle size, consider slowing down your reps and focusing on form and control. Heavy lifting still has benefits for strength, but if you want visible growth — slow it down to blow up.