The Morin-Samozino Sprint Method: A Practical Field Guide
Summary
The Morin-Samozino method turned sprint force-velocity profiling into a field test. Here's a step-by-step practical guide to applying it correctly.
Jean-Benoît Morin and Pierre Samozino have produced some of the most practically significant work in applied sprint science of the past two decades. Their method for deriving the force-velocity profile from a series of field sprints is now widely used — but frequently applied incorrectly. This guide covers what the method actually requires and how to get reliable output from it.
The Core Principle
The method is built on the observation that when an athlete sprints against different resistances, they generate different combinations of force and velocity. Heavier loads produce more force but less velocity; lighter loads produce less force but more velocity. Plot those data points and fit a line: that line is the athlete's force-velocity profile.
From the line, you can extract:
- F₀: The theoretical maximum force (at zero velocity)
- V₀: The theoretical maximum velocity (at zero force)
- Pmax: The maximum power output (F₀ × V₀ ÷ 4)
- FVimb: The force-velocity imbalance index, which compares the actual slope to the theoretically optimal slope for that Pmax
Samozino (2018) provides the full derivation in the edited volume *Biomechanics of Training and Testing*. The short version: the method works because the force-velocity relationship in sprint running is approximately linear across the loads tested, allowing the linear regression to be valid and the extrapolations to F₀ and V₀ to be reasonable.
Equipment Needed
- Body mass scale (measured on the day, with training gear)
- Sled with known friction properties for your surface
- Velocity measurement per condition — options include:
- Timing gates (mean velocity over a split)
- Radar gun (measures instantaneous velocity)
- Validated inertial measurement device
- Stopwatch/timing system for recovery management
Step-by-Step Protocol
Pre-session (day before or morning of):
- Confirm the surface you will use for all conditions
- Know the friction coefficient of your surface for the sled in use
- Measure and record athlete body mass
Warm-up:
- 15–20 minutes general warm-up
- 2–3 submaximal acceleration runs
- 1 near-maximal sprint (no sled) — this is not a test condition, it is preparation
Testing conditions:
Run 4–5 sprint conditions in the following order (by convention, lightest to heaviest):
1. Unloaded (no sled, or empty sled towed)
2. Light load (~10% velocity decrement)
3. Moderate load (~25% decrement)
4. Heavy load (~40% decrement)
5. Very heavy load (~55% decrement) — optional
Each sprint: 20–30 m distance, from a standing start, maximum effort throughout. Record mean velocity over the measured section (typically the first 15–20 m to capture the acceleration phase).
Recovery: 4–5 minutes between every condition, no exceptions.
Data recording:
For each condition: load applied (kg), calculated horizontal force (N = load × g × µ), mean velocity (m/s).
Running the Regression
Enter your force-velocity data pairs into a spreadsheet or profiling app. Confirm the R² of the linear fit — this is your quality check. R² ≥ 0.95 indicates acceptable protocol quality. Below this, examine your conditions for outliers before interpreting the profile.
Extract F₀, V₀, Pmax, and FVimb. Record these alongside the R² for each session.
Common Protocol Failures (and How to Avoid Them)
Failure | Consequence | Fix
Short recovery | Fatigue inflates force deficit | 4–5 min, no shortcuts
Inconsistent start | High inter-sprint variability | Mark foot position, same every time
Wrong friction coefficient | Systematic load error | Verify coefficient for your surface
Only 2 conditions | Poor regression | Minimum 3, prefer 4–5
Tracking Progress
Re-test every 8–12 weeks or at the end of each training block. The profile shift tells you whether training has moved the needle in the intended direction. An athlete targeted for force development should show F₀ increasing and FVimb moving toward 1.0 from a position above it.
References
Mark Fisher
Founder, Swift Performance
Mark Fisher is the founder of Swift Performance and has spent 30 years designing and building athlete testing equipment used by elite sport programmes and universities worldwide. He has worked alongside researchers and PhD candidates across biomechanics, sprint mechanics, and strength science — developing the hardware and software they use to collect and analyse performance data. His writing comes from three decades at the intersection of applied sport science and precision measurement technology.
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