If you've ever wondered whether you should rest 1 minute or 3 minutes between sets, the answer is: it depends. And that's exactly why we built an adaptive rest timer into Swole.
The Research on Rest Periods
Let's start with what the science actually says.
For Strength Gains
A landmark 2016 study by Schoenfeld et al. compared 1-minute vs. 3-minute rest periods over 8 weeks of training. The results were striking:
- Squat 1RM: 3-minute group gained 15.3% vs. 7.5% for 1-minute group
- Bench 1RM: 3-minute group gained 12.7% vs. 4.1% for 1-minute group
That's nearly double the strength gains just from resting longer.
The mechanism is straightforward: longer rest allows better recovery of the phosphocreatine system and removal of metabolites, letting you lift heavier on subsequent sets.
For Hypertrophy
Here's where it gets interesting. Traditional bro-science says short rest builds more muscle. But Singer et al.'s 2024 Bayesian meta-analysis found that rest periods over 60 seconds produce similar hypertrophy outcomes.
The key insight: metabolic stress isn't the primary driver of muscle growth—mechanical tension is. As long as you're hitting your volume targets, rest period length matters less for hypertrophy than for strength.
Why One Timer Doesn't Fit All
The problem with static rest timers is they ignore context. Consider these two scenarios:
Scenario A: You just hit 5 reps of squats at RPE 8. It was challenging but you had 2 reps in the tank.
Scenario B: You just hit 5 reps of squats at RPE 10. It was a grinder, and you failed the 6th rep.
Should both sets get the same rest? Obviously not. Scenario B needs significantly more recovery time.
How Swole's Algorithm Works
Our adaptive rest timer considers four factors:
1. RPE (Rate of Perceived Exertion)
RPE is the foundation. Higher RPE means more fatigue, which means more rest needed.
- RPE 10: +60 seconds to base rest
- RPE 9: +30 seconds
- RPE 8: +15 seconds
- Below RPE 8: Standard rest
2. Exercise Category
Different movement patterns have different recovery demands:
| Category | Strength Base | Hypertrophy Base |
|----------|---------------|------------------|
| Lower Heavy (squat, deadlift) | 240s | 150s |
| Upper Heavy (bench, row) | 180s | 120s |
| Accessory/Isolation | 120s | 75s |
Compound movements that load the spine and larger muscle groups simply need more recovery than isolation work.
3. Your Training Goal
This adjusts the bounds of rest:
- Strength focus: 120-300 second range
- Hypertrophy focus: 60-180 second range
- General fitness: 90-240 second range
4. Rep Performance
Did you hit your target reps? If you completed fewer than 75% of target, you need more rest. If you exceeded your target, you can probably shorten rest slightly.
An Example Calculation
Let's say you're running 5/3/1 for strength and just finished your 5+ set of squats:
- Target: 5 reps
- Actual: 6 reps
- RPE: 9
- Exercise: Lower heavy compound
Calculation:
- Base rest (lower heavy, strength): 240 seconds
- RPE 9 modifier: +30 seconds
- Exceeded target reps: -15 seconds
- Total: 255 seconds (4:15)
Compare that to a bicep curl at RPE 7: you might get 90 seconds.
The Bottom Line
Rest periods matter more than most lifters realize, especially for strength. The research is clear: if you're chasing strength PRs, you should be resting 3+ minutes on heavy compounds.
But you don't need to think about this. Just log your set, report your RPE, and let Swole calculate the optimal rest. It's one less thing to manage so you can focus on lifting.
Want to try the adaptive rest timer? Download Swole for $5 and see the difference smart rest makes.