If you’ve ever stood around in the gym staring at your phone, wondering if you’re resting too long (or not enough), you aren’t alone. For decades, the “bro-science” consensus was simple: short rest periods for building muscle (hypertrophy) and long rest periods for building strength.

However, a new study is challenging this old dogma, suggesting that the timer on your phone might matter less than you think—provided you understand the real driver of muscle growth.

Here’s what the latest science says about rest intervals and how you can use it to build more muscle in less time.

The Old Rule vs. The New Science

Traditionally, lifters were told to keep rest intervals short (around 60 seconds) to maximize “metabolic stress” and the hormonal pump. However, modern physiology has largely debunked this. We now know that temporary hormonal spikes and metabolic stress are not the primary drivers of muscle growth.

The real driver of hypertrophy is mechanical tension.

In simple terms, muscle grows when it is subjected to high levels of tension for a sufficient amount of time. This is effectively calculated by the weight on the bar multiplied by your total repetitions (time under tension).

What the New Study Found

A recent study compared two groups performing leg extensions:

1. Long Rest Group: 2 minutes of rest between sets.
2. Short Rest Group: Only 20 seconds of rest between sets.

Crucially, the researchers equated the total volume. Even though the short-rest group had to do significantly more sets (because their muscles were fatigued), both groups performed the exact same total number of repetitions with the same weight.

The Result: After 10 weeks, there was no significant difference in muscle growth or strength gains (42% increase for both).

Quality Over Clock: Why Volume Wins

This study reveals a critical principle for your programming: Total volume drives growth, not the rest interval itself. This aligns with the foundational concept of progressive overload—the key driver of all muscle growth.

In previous studies where long rest periods seemed superior, it was often because the long-rest group could perform more reps. If you rest 3 minutes, you might hit 10 reps on your second set. If you only rest 1 minute, you might only grind out 6 reps. Over weeks, the long-rest group accumulates way more volume, leading to more growth.

But, as this new study shows, if you compensate for the fatigue by adding more sets—ensuring you hit the same total reps—short rest periods can be just as effective.

SetsApart automatically tracks your total reps per exercise, making it easy to ensure you’re hitting your volume targets regardless of rest intervals. This takes the guesswork out of whether you’re doing enough work.

The “Time-Efficiency” Hack: Rest-Pause and Myo-Reps

While short rest intervals require more sets to get the same work done, they are drastically more time-efficient.

In the study, the short-rest group had to perform nearly double the sets (roughly 6 sets vs. 3 sets) to match the volume of the long-rest group. However, they finished their workout in less than half the time (3 minutes vs. 7 minutes).

This validates advanced training techniques like Rest-Pause or Myo-Reps.

• How to do it: Instead of doing 3 sets of 10 with long breaks, you pick a target number of reps (e.g., 30 reps total).
• Do your first set near failure.
• Rest only 15-20 seconds.
• Do another mini-set to failure.
• Repeat until you hit 30 reps.

This method allows you to cram the same growth stimulus into a fraction of the time.

When You Should Still Rest Longer

Before you switch everything to 20-second breaks, there is a caveat. For strength athletes or those lifting very heavy on compound movements (like squats or deadlifts), very short rests may be detrimental.

When you train to failure, your high-threshold motor units (which control your biggest, strongest muscle fibers) drop out. It can take 3 to 5 minutes for your energy systems (specifically ATP-CP) to recharge. If you rush into the next set too quickly, you may not be able to recruit these high-growth fibers, limiting your top-end strength potential.

Practical Takeaways for Your Workout

You can’t set your rest intervals and set volume independently; they interact with each other. Here’s how to apply this to your goals:

1. For Maximum Performance (The “Optimal” Approach)

If you have the time and want to ensure every set is high quality, use autoregulation. Rest until you feel fully recovered and ready to perform at your best. This typically means 2-3 minutes or more for big lifts. SetsApart includes a built-in rest timer that helps you track your rest periods without watching the clock. You won’t need to do as many sets because your rep counts will remain high set-to-set.

2. For The Busy Lifter (The Time-Saver)

If you need to get in and out of the gym, stop worrying about the clock. Focus on Total Reps. For more on maximizing gains with limited time, check out our guide on the minimum effective dose for muscle growth.

• Take your usual workout weight.
• Determine your total target reps (e.g., if you usually do 3x10, your target is 30).
• Get to 30 reps in as few sets as possible with short rests (20-30 seconds) in between.

Use SetsApart to set your rep target and track progress across mini-sets when using rest-pause techniques. The app shows your running total so you know exactly when you’ve hit your goal.

Summary

Don’t obsess over the exact seconds on your rest timer. Focus on the total work you are putting in. Whether you take long breaks to recover or short breaks to save time, as long as the total mechanical tension is high, your muscles will grow.

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Source

This article was inspired by and summarizes key insights from the following video. You should check out the video for more detail and subscribe to the channel. It’s a great resource for muscle building.

Watch the full video: How Long Should You Rest Between Sets?