The Force-Velocity Curve
Key Takeaway Points (TLDR):
1. The force-velocity curve is the inverse/negative relationship between muscular contraction force and velocity. Contractions can either have high levels of relative force or high levels of relative velocity but neither of them simultaneously.
2. The conventional goal with resistance training for athletic development and sport performance is to increase the entire area under the curve (improved force and velocity). This allows the athlete to improve both types of athletic expression.
3. Training aimed towards improvements in maximal force tend to improve most of the curve even including much of the higher velocity end of the curve.
4. Conversely, any specific improvements in maximum velocity tend to fail to improve the higher force end of the curve.
5. Training and/or practice aimed towards specific improvements in maximal velocity tend to be short-term improvements with very limited ability to be progressed across longer periods of training.
6. If long-term, high-quantity improvements in the major underlying adaptations responsible for both high force and high velocity muscular outputs are desired (as is the case with young competitive athletes), then the primary focus for most of the training calendar should be high force training.
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The force-velocity curve describes the inverse relationship between a muscle’s ability to contract forcefully (i.e., high strength) or quickly (i.e., high speed). It is important for coaches and athletes to understand the force-velocity curve and how it behaves with various modes of resistance training because it informs subsequent best methodologies. Simply stated, the negative relationship between force and velocity means that as the demand for force increases, velocity predictably decreases; and inversely, as the demand for force decreases, velocity is allowed to increase. Image below:
Force-Velocity Curve of Muscular Contraction
This concept is demonstrably very simple. You can always throw a baseball faster (therefore, further) than a bowling ball. You can push a grocery cart faster than a car. And, if you took equally maximal attempts at throwing 3 kg, 4 kg, 5 kg, and 6 kg shot puts, you would throw them in that exact order for maximum distance. Once more, force and velocity are inversely proportional. While this may be a simple concept, there is much misunderstanding regarding how strength training interacts and changes the curve for any given athlete.
An athlete’s goal should virtually always be to shift the force-velocity curve up and to the right. This creates greater area under the curve, and ultimately means the athlete can produce more maximal force, maximal velocity, and more velocity at any given level of force along the curve that is submaximal. Image below:
Positive Shift of Force-Velocity Curve from Training
Some nuances need to be understood with any attempt to shift this curve into the direction of improved performance. First, there is a “trickle-down effect” that tends to occur. That is, improvements in the higher force side of the curve tend to lead to improvements down the curve in the direction of higher velocities. These increased forces tend to “trickle-down” into increased velocity. Thusly, training for improved force production will tend to improve both force and velocity—a very economical benefit.
Secondly, the previous “trickle-down effect” is largely a one-way road—acting in a downward direction. There is virtually no “trickle-up effect.” Training resources invested in attempting to directly improve the velocity side of the curve will not improve higher force productions. Therefore, high-velocity muscular contractions are, at best, less economical in that there are not simultaneous improvements at both ends of the curve. Unfortunately, high velocity “training” (not to be mistaken for the benefits of “sport practice”) may be even bleaker given our last nuance.
Barring short-term improvements in motor learning and muscular coordination, solely training high velocity movements does not tend to improve muscular contraction speed in the long-term. Once more, some minor neurological improvements (e.g., rate coding/discharge rate) can be made when directly training high velocity contractions, however these are only short-term improvements typically amongst more untrained individuals and these will not continuously improve over a long-term training program. Furthermore, these adaptations can be improved by other more productive means such as the aforementioned conventional high force training methods. All of this is to say that high velocity training is often not the best allocation of training resources. This is especially true if the athlete is already participating in high-velocity sport practices.
In brief conclusion, training targeting the high force side of the force-velocity curve is generally more productive and fruitful in the long-term within developing athletes who are already playing sports. High velocity muscular contractions are allowed when the external force requirements of a task are lower than the available surplus of force/strength. This can be elucidated with a simple example: a 300-pound max bench presser will always move 200 pounds more quickly than someone whose max is exactly 200 pounds. Everything else held equal, bigger engines tend to lead to faster speeds. Improving your strength-to-weight ratio will always be the holy grail of speed training, not generic and ubiquitous “speed & agility” programs.