What prompted this discussion
Recently, I worked with an athlete who presented an interesting combination of characteristics:
- Relatively low concentric impulse at 100 ms
- Better concentric impulse at 200 ms
- Relatively low eccentric utilization ratio (EUR)
This created an interesting programming question: Should we use Olympic lifting or flywheel training? My answer was: Why choose one? Instead, I used Olympic lifting and low-inertia flywheel training to attack different parts of the athlete’s force-time problem.
Start with impulse, not the exercise
Impulse is the integral of force over time. In simple terms: Impulse = Force × Time. But the important part for performance is not just total impulse. When does the athlete produce that impulse? An athlete can eventually produce a large amount of force and impulse but still struggle to produce enough force during the first 100 ms. That athlete may appear strong on traditional strength measures yet still have a limitation in rapid force expression. This is why I like looking at concentric impulse at different time intervals.
- 100ms – Provides information about the athlete’s ability to rapidly accumulate force early in the contraction.
- 200ms – Provides a longer window for force accumulation.
The relationship between these measurements can tell us something that a single peak-force measurement cannot.
But then we have EUR
Eccentric Utilization Ratio, or EUR, is generally calculated by comparing countermovement jump performance with squat jump performance. If you haven’t read my book on leveraging EUR in practice, you should read Strength Deficit – it will help unpack this concept a lot.
A higher EUR means the athlete receives a greater performance benefit from the countermovement. It is tempting to assume: Higher EUR = better athlete. The whole point of Strength Deficit is to say that is not always true. For example, a wide receiver in football will need a much larger EUR than an offensive lineman. That makes sense. If the sport requires frequent rapid eccentric-to-concentric transitions, the ability to utilize the stretch-shortening cycle may be highly valuable. But that doesn’t mean every athlete should have a high EUR. Context matters. An athlete may benefit from being relatively independent of a large countermovement. Think about sporting situations where the athlete must produce force with limited preparatory movement:
- contact situations
- pushing and bracing
- short-area acceleration
- overcoming resistance
- certain static or quasi-static positions
In these situations, the ability to produce force concentrically without requiring a large eccentric contribution may actually be useful. There is even emerging evidence challenging the assumption that a higher EUR necessarily represents superior explosive performance. A 2024 exploratory study found that higher EUR values were associated with poorer squat-jump RFD, suggesting that greater reliance on the countermovement does not necessarily indicate superior rapid force development. So I don’t necessarily want to “fix” a low EUR. Instead, I want to ask: Is the athlete appropriately low EUR for the demands of their sport, but simply not producing enough concentric impulse quickly enough?
Low EUR + Low 100-ms Impulse
An athlete was not particularly dependent on the countermovement. But they may not be producing enough concentric impulse early in the movement. That changes the intervention. The objective isn’t: Increase EUR.
The objective is: Improve concentric impulse while preserving an appropriate eccentric utilization strategy.
In other words:
- We don’t necessarily want: Low EUR → High EUR
- We may want: Low EUR + Low P1 to become: Low EUR + High P1
Why P1 and P2 Matter
Where is the athlete producing their power? Conceptually, we can think about the concentric phase as having different portions of the force-time relationship.
- P1 – The early portion of propulsion.
- This is where the ability to rapidly initiate force production becomes important.
- P2 – The subsequent portion of propulsion.
- This is where the athlete continues to apply force and accumulate impulse.
Enter Olympic Lifting
Olympic lifting provides an interesting solution because it combines:
- External load
- High force production\
- Acceleration
- Ballistic intent
- Coordination of force production through a high-velocity movement. Weightlifting should not be thought of simply as “heavy strength training.”
Elite weightlifters demonstrate very high rates of force development, and a 16-week periodized weightlifting program has been shown to improve RFD specifically in the 0–200 and 0–250 ms windows, whereas peak force did not change significantly. That’s particularly interesting when we’re thinking about an athlete with a 100–200 ms impulse problem. The Olympic lift provides a way to expose the athlete to high-force, high-velocity acceleration. Dumbbell and kettlebell variations are appropriate and can bring a ton of value.
Then Why Flywheel?
This is where low-inertia flywheel training becomes interesting. A low-inertia flywheel allows the athlete to generate extremely high movement velocities while accelerating the rotating mass.Instead of primarily asking: “How much external resistance can you move?” we can ask: “How rapidly can you accelerate the system?” This creates a different stimulus. The athlete can be exposed to:
- High velocity →
- High acceleration →
- Rapid concentric force expression →
- High propulsive velocity
That is potentially useful when the athlete’s limitation is not their eventual ability to produce force, but their ability to express that force rapidly. Research supports the idea that flywheel loading can be individualized through velocity. Subject-specific relationships between flywheel inertia and concentric velocity have been demonstrated, supporting the use of concentric velocity as a useful method for prescribing and monitoring flywheel intensity.
So Why Use Both?
This is where the programming decision becomes clear. Olympic lifting and flywheel training are not competing modalities. They are providing different solutions to the same force-time problem.
Olympic lifting – Force + load + acceleration + impulse
The athlete must produce force against meaningful external resistance while rapidly accelerating the load.
- Low-inertia flywheel – Velocity + acceleration + rapid concentric expression. The athlete can reach very high propulsive velocities while accelerating the inertial system.
- EUR is a constraint/characteristic—not necessarily an adaptation target. Monitor whether the athlete’s eccentric utilization strategy is appropriate for the demands of the sport. Programming decision becomes clear. We need to provide different solutions to the same force-time problem.
The Bigger Lesson:
The biggest takeaway from this case isn’t: Flywheel is not better than Olympic lifting. Olympic lifting is not better than flywheel training. It’s this: Exercise selection should follow the athlete’s force-time problem. The modality is the tool. The athlete’s profile is the diagnosis. A relatively low EUR was not something we want to automatically change. The issue could be how quickly that impulse could be expressed. That will lead to a combination of Olympic lifting to provide meaningful force and impulse under load, and low-inertia flywheel training to provide high-velocity concentric acceleration.
The primary goal should be to improve the athlete’s ability to express concentric impulse rapidly without assuming that they need to become more eccentric-dependent.
