Force-Velocity Profiling: What It Is, Why It Matters, and How to Do It Right
Summary
Force-velocity profiling tells you exactly where an athlete's power production breaks down — and therefore exactly where to direct their training. Here's how it works and why getting it right matters.
Force and velocity exist in opposition. The harder a muscle contracts, the slower it can move. The faster it moves, the less force it can produce. This is the force-velocity relationship, and every athlete sits somewhere along it — usually closer to one end than the other.
Force-velocity profiling (FVP) quantifies exactly where that is. It maps an athlete's ability to produce force across a range of velocities, giving you a curve rather than a single data point. That curve tells you something a vertical jump height or a 10-metre sprint time simply cannot: the *shape* of their power deficit.
Why This Matters More Than a Single Test
Coaches have always known that some athletes are "strength-limited" and others are "velocity-limited." FVP puts numbers on that intuition. An athlete who is force-deficient has a profile tilted toward the velocity end — they accelerate quickly but struggle to produce high absolute forces. The velocity-deficient athlete is the opposite: they can grind out force but cannot apply it at speed.
This distinction has direct training implications. Putting a velocity-deficient athlete through a heavy sled programme will reinforce their existing profile. Putting a force-deficient athlete on light, high-speed resisted sprints will do the same. The research of Jean-Benoît Morin and Pierre Samozino — particularly their 2016 framework — showed that athletes with the most imbalanced profiles made the largest gains from targeted training, while athletes who were already well-balanced gained less from any single intervention (Morin & Samozino, 2016).
How Force-Velocity Profiling Works in Sprint Testing
The Morin-Samozino method uses a series of sprint conditions at different resistances to plot the force-velocity curve. In its simplest form, this requires a series of maximal effort sprints — one unloaded and at least two to three at increasing sled loads — while measuring velocity at each condition. The resulting data points are fitted to a linear regression, giving you the theoretical maximum force (F₀) and maximum velocity (V₀), and from those, maximum power (Pmax).
What makes this method powerful is that it requires no laboratory equipment. A set of timing gates or a radar gun plus a friction-resistance sled is sufficient. The critical requirements are:
1. Genuine maximal effort at every condition. Any reduction in intent contaminates the curve.
2. Adequate recovery between sprints. Fatigue shifts the curve and produces a false profile.
3. Accurate mass measurement, including the sled and any additional load.
4. Consistent surface conditions. A wet track or uneven ground changes the drag coefficient.
Common Profiling Errors
Cross et al. (2017) identified that poorly controlled profiling conditions — particularly inadequate recovery and inconsistent starting positions — produce profiles with high test-retest variability. If your profiles are jumping around between sessions, the problem is almost always protocol, not the athlete.
The other common error is over-interpreting small differences. An F-V slope difference of 0.1 between two athletes may be within measurement noise. Context matters: profiling is most useful when tracking the same athlete over time, or when comparing a large group.
The Practical Output
At the end of a profiling session you have three numbers that mean something concrete:
- F₀: Maximum theoretical force (at zero velocity)
- V₀: Maximum theoretical velocity (at zero force)
- Pmax: The peak of the power curve, sitting at roughly F₀/2 and V₀/2
The *force-velocity imbalance* (FVimb) index quantifies how far the athlete's actual profile deviates from an "optimal" profile for their Pmax. An FVimb above 1.0 indicates a force deficit; below 1.0 indicates a velocity deficit.
Use this to direct training, not to judge athletic potential. The profile changes with training — which is exactly the point.
References
Mark Fisher
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