Glossary

SFR (Stimulus-to-Fatigue Ratio)

Training Efficiency Fatigue

More net growth for less cost: prioritize exercises that create high target-muscle tension with low systemic fatigue.

Notice

This page provides context and guardrails. It is not individual medical, nutrition, or training advice. Suitability and tolerance are individual; for pre-existing conditions, pregnancy/lactation, or medication, consult qualified professionals before making changes.

Term and System Context

Exercise SelectionQuality

SFR describes the ratio of stimulus to fatigue. The aim is to choose exercises/setups that, per unit of fatigue, produce maximal tension in the target muscle. For hardgainers (limited recovery resources), SFR is a primary filter for exercise selection and volume planning.

Notice

Matching deep-dives: Myth #2 – “More training = more muscle” • Myth #9 – “No pump, no muscle growth”.

Heuristics for High SFR

  • Stability & fixation: chest-supported/back-supported setups and machines raise target tension time; unstable setups lower SFR.
  • Lengthened tension: exercises loading the muscle in the stretched position (e.g., lying leg curl, incline curls) often deliver more stimulus.
  • Lower bracing cost: the less whole-body bracing/lower-back load needed, the better the SFR.
  • ROM & control: full, reproducible ROM & tempo > “cheat” reps.
  • Read markers correctly: pump is secondary; performance progress at similar RIR is primary.
  • Protect joints: unpleasant shear/pain → SFR drops; pick alternatives.

Practice: Exercise Selection (Examples)

TargetHigher SFRLower SFRWhy
Quads Hack squat, pendulum, leg press (narrow), leg extension Low-bar back squat, front squat (for many) More stability, less bracing cost, steadier target tension
Back (rhomboids/lats) Chest-supported rows, seal row, cable rows with chest support Freestanding bent-over barbell rows Less lumbar limitation → more reps in the target muscle
Posterior chain RDL, hinge machines, glute bridge/HS curl Conventional deadlift for hypertrophy Lower systemic fatigue per unit stimulus
Shoulders (ant./lat.) Machine/seated DB press, cable laterals Standing OHP (long blocks) More stable, fewer technique/bracing failures
Biceps Incline DB curls, cable curls (constant) Heavy “cheat” curls Constant tension, less momentum

Individual anthropometry matters. SFR is a guideline, not dogma.

Control Logic and Markers

  • Performance trend @ fixed RIR: reps/load rise at RIR 1–2 → SFR fits; stagnation despite technique → audit exercise/setup.
  • Fatigue feedback: local fatigue > systemic exhaustion; sleep/libido stable.
  • “Bracing score” (1–5): many high-score sets → SFR drops; favor supported alternatives.
  • SRA fit: target muscle recovers in 48–72 h (per muscle/volume); otherwise adjust volume/exercise.
  • Technique drift: increasing drift → SFR falls; adjust load/tempo/setup.
Safety

If you have pain, injuries or medical conditions, seek medical clearance before changing exercise/load/frequency.

Common Mistakes

  • Making “hero” lifts the default: heavy deadlifts/squats every session → systemic fatigue eats progress.
  • Instability as a feature: BOSU/single-leg variants for hypertrophy → SFR collapses.
  • Only adding sets: instead of progressing at constant technique → junk volume.
  • Ignoring anthropometry: unfavorable levers → poor SFR; swap the exercise, don’t just “push harder”.
  • Chasing pump as the goal: forgetting tension/performance → weak net output.
MYTH #2

“More Training = More Muscle”

False. Growth = Stimulus × Recovery — not sets × ego. Quality beats quantity: prioritize mechanical tension near failure (RIR 1–2), stable technique, and planned progression within the SRA window. Work from MEV → MAV, avoid junk volume, deload as needed. Read more: Myth #2.

MYTH #9

“No Pump, No Muscle Growth”

False. The pump is an acute response (blood volume, cell swelling) and correlates poorly with long-term hypertrophy. The driver is mechanical tension near failure (RIR 1–2), stable technique, and planned progression within the SRA window. Use the pump as feedback, not the goal. Work from MEV → MAV and avoid junk volume. Read more: Myth #9.

Interactive SFR Set Designer

For an interactive evaluation of your sets, you will find the SFR Set Designer inside the Training Volume and Fatigue System .

Feature Article

Training Volume and Fatigue System – Volume, Fatigue, and Recovery at a Glance

The Training Volume and Fatigue System shows how volume (MEV, MV, MAV, MRV, Junk Volume), fatigue (SFR, RIR/RPE) and recovery (SRA, Deload) shape your programming – clear orientation guardrails, not rigid prescriptions.

Ideal as a home base when you want to structure volume cycles, plan deloads, and run progression as a programming brain instead of pure intuition – especially in a hardgainer context.

🔎 View Training Volume and Fatigue System
Practice

You do not just want to understand 1RM, RIR and volume – you want them wired into a structured plan? Then use the Hardgainer Training Plan Generator.

Hardgainer Training Plan Generator

No guesswork: setup → volume → RIR – structured, visualized, hardgainer-specific.

  • Setup selection: Barbell/dumbbell, home gym or commercial gym.
  • Split & frequency: Muscle-group and weekly structure in a system.
  • Level: From beginner to advanced – clear guardrails.
  • Volume per muscle: Sets within the MEV–MAV range.
  • RIR/RPE targets: Control set difficulty per exercise.
  • SFR focus: Exercise selection with a strong stimulus-to-fatigue ratio.
  • CNS & fatigue gauge: Load overview at a glance.
  • Weekly overview: Structured plan instead of random sets in chaos.
  • Guides & glossary: Embedded in the Training Volume & Fatigue System.
📋 Generate your training plan
Training Volume & Fatigue System RIR – Reps in Reserve

Reference ranges → fine-tuning via progression, biofeedback and 4–8 week mesocycles.

Notice

Descriptive information for orientation — not a treatment, diet or training prescription. Individual differences and possible contraindications apply.

© Hardgainer Performance Nutrition® • Glossary • Updated: Nov 25, 2025