What is the Stimulus-to-Fatigue Ratio (SFR)?

🎯 What is the Stimulus-to-Fatigue Ratio (SFR)?

SFR, coined by Dr. Mike Israetel, compares how much training benefit (“stimulus”) you get to how much stress or tiredness (“fatigue”) it causes. The goal? Maximize muscle/strength gains while keeping unnecessary fatigue low  .

It’s the “muscle-pump vs joint-tank” ratio—training smarter, not harder.

🧠 SFR in Plain English

Stimulus = the good stuff (muscle growth, strength gains, endurance).
Fatigue = the recovery cost (soreness, joint stress, central nervous system burnout).

Fatigue isn’t all bad—it’s part of the growth puzzle—but not every workout needs to wreck your recovery.

🚦 Why SFR Matters

More stimulus, less recovery pain = faster progress with fewer setbacks. Fatiguing workouts require more extended recovery periods and taper gains. Over time, you become fitter—your body adapts and handles the same work with less fatigue.

Here’s how to apply SFR to your training:

1. Choose Better Exercises
Swap high-fatigue, low-stimulus moves like conventional deadlifts for more efficient ones like Romanian deadlifts or chest-supported rows—same muscle work, less systemic wear-and-tear. Prefer machines or cables for isolation work—targeted stimulus with minimal joint stress.

2. Lift Smart, Not Just Heavy
Go for that sweet spot of 8–30 reps. Super-heavy loads spike fatigue; low-weight, high-rep sets can turn into “junk volume”. Avoid sets that lead to complete failure all the time—RPE 7–8 is often enough to trigger growth without compromising recovery.

3. Order Sets Strategically
Do fatiguing lifts early (when you’re freshest) or prime your nervous system with light activation sets before more challenging moves.

4. Track & Adjust Volume
Start with a moderate volume—around 10 sets per large muscle group weekly, and 5–6 sets for smaller muscles. Increase only if you’re recovering well and making progress; dial back if fatigue accumulates.

5. Prioritize Recovery
Build in deloads, rest days, or lighter phases. Fatigue management is part of the plan.
 
🔥 Anton’s Coaching Take
Pick smarter exercises—I love Romanian deadlifts over barbell deadlifts for hamstrings: solid stimulus, way less fatigue. Go moderate—stay in the 8–20 reps range, skip chasing failure. Plan recovery—schedule deloads every 4–12 weeks and monitor your energy levels.

This is the secret sauce: train hard but recover smart, with results that speak for themselves.

🔗 Credit Where it’s Due:

Adapted from How to Optimize Your Stimulus-to-Fatigue Ratio (SFR) by Shane Duquette & Marco Walker-Ng from Outlift (Sep 16, 2024), plus insights from Hevy Coach, Biomechanics Coach, REfit, and Mind Muscle Training. https://outlift.com/stimulus-to-fatigue-ratio-sfr/

 🎉 Final Thought

Want to grow stronger without burning out? Start using SFR as your training compass. I can build your next plan around strong, efficient lifts and smart recovery—perfect for busy lives and big goals.

Ready to lift smarter? Hit email me, DM me on IG and if you're already my client, then drop me a message on Trainerize.

Train smart, grow hard,
Coach Anton