Velocity loss & fatigue
The cleanest single number for "how much fatigue is in this set", and the autoregulation metric that holds up best with real athletes.
Velocity loss is the percentage drop in mean concentric velocity from the fastest rep of a set to the current rep. Cross a chosen cutoff and the set ends — regardless of how many reps the program said to do.
It works because it’s the closest thing we have to a direct read of intra-set fatigue. RPE tries to estimate it after the fact. Reps-in-reserve tries to predict it before. Velocity loss measures it as it happens.
Velocity loss across a working set
Why it works better than RPE
- Objective. No subjective rating, no scale calibration drift between athletes.
- Real-time. You see the cutoff coming on rep 5 of the set, not in the journal review afterwards.
- Comparable across sessions. Two sets to the same v-loss target are matched for fatigue regardless of load, reps, or how the athlete felt that day.
Common cutoffs by goal
| Goal | Typical cutoff | Why |
|---|---|---|
| Power / speed | 5–10% | Stop while reps are still fast and fresh |
| Strength | 10–20% | Productive volume without grinding |
| Hypertrophy | 20–30% | Mechanical tension over fresh velocity |
| Capacity / GPP | 30%+ | Buffer-burning sets, accept some grinder reps |
These are starting points, not laws. Calibrate to your athlete. A powerlifter on a peaking week probably wants 10% even on hypertrophy days; a beginner doing 3×8 squats might safely take 30% v-loss every session.
What it changes about training
Two consequences fall out of using v-loss as the cutoff:
- Volume self-regulates. A fresh athlete gets more reps to the same cutoff than a fatigued one. The training stress equalises across days that would otherwise look very different in the journal.
- Overreaching shows up early. When yesterday’s cutoff came after 6 reps and today’s came after 3 at the same load, you have hard evidence that the athlete needs to back off — before performance drops or injury risk climbs.
Looking for the protocol? Picking a cutoff for a specific block, calibrating it across athletes, and integrating it into a program template is its own write-up.
Velocity loss guidelines for fatigue with VBT
Articles in this topic
VBT log: Planning deloads from velocity data
Last rep velocity & RPE: Autoregulated strength training with VBT
Is overtraining hurting your strength and muscle gains
Should you train to failure? The risk/reward, by goal
Velocity based training for strength
Autoregulation and readiness with velocity based training
Adapting Dan John's rule of ten to velocity based training
Velocity loss threshold: Fatigue percentage guidelines for VBT
Applications and example uses of velocity based training (VBT)
Charts in this topic
Bar velocity drops across a set
Per-rep velocity loss for a single working set. The cutoff line marks where the set should end.
Minimum velocity threshold by lift
Minimum velocity threshold values for back squat, front squat, bench, all three deadlifts, barbell row, and overhead press — by training level (novice / elite) and by effort tier (max out / tough / moderate).
20% velocity loss maximises strength
Pareja-Blanco 2017 — squat 1RM gains scale with the velocity-loss cap inside each set. Strength response peaks around 20 % v-loss, then drops as fatigue overruns adaptation.
Training to failure slows jump recovery
Gonzalez-Badillo 2016 — jump performance crashed 44 % immediately after a higher-effort squat workout (3×8) and stayed depressed for 48 hours; the lower-effort 3×4 group bounced back inside 6 hours.
Lower velocity loss, better gains
Pareja-Blanco 2016 — training to 20 % velocity loss out-gained 40 % on 1RM, bar velocity, jump, and type-II muscle fibres, while doing significantly less total volume.
Feedback beats internal & external cues
Keller 2014 measured two outcomes from the same three-condition study — acute jump output and within-set fatigue. Augmented feedback won both — ~4× more acute improvement than the best verbal cue, plus an inverted within-set fatigue curve.
RPE conversion chart
All four common effort languages on one chart — RPE 5.5–10, RIR 5–0, velocity loss 5–45 %, last-rep velocity 0.52–0.25 m/s. Drop a finger on any row to read across.