From Load to Velocity: Importance of ‘Time’ in force expression

Traditional strength training often overlooks the critical role of time in force production. This article explores how velocity-based training technologies can help athletes and coaches align strength development with the real demands of sport performance.

By Valerio Esposi to

Content menu:

Introduction
Athletic Performance and the SAID Principle
Bosco’s Classification of Strength Expressions
Understanding the different types of Strength
The Role of Time in Force Expression
Linking Strength Expression to Average Velocity
Practical contribution of VBT technology
Rethinking Traditional Strength Training: Insights from Vern Gambetta
Conclusion

Introduction

In the strive towards peak athletic performance, understanding how force is expressed over time is as important as the amount of force produced. Traditional strength training often emphasizes maximal loads, yet sport-specific movements typically demand quick force production within short time frames. This disconnect highlights the need to reconsider how we define and measure strength. Building on foundational principles such as Bosco’s classification of strength types and the SAID principle, this article explores how technology like GymAware RS and FLEX can optimize training by capturing the velocity and duration of force application; offering coaches and athletes a more precise, performance-driven approach to strength development.

Athletic Performance and the SAID Principle

The ultimate goal of every physical preparation program for strength and conditioning is to maximize athletic performance, and as mentioned in the previous article, the SAID principle indicates that our training reference should be what happens in competition.

Bosco’s Classification of Strength Expressions

In 1997, Professor Carmelo Bosco, in his masterful publication “La forza Muscolare” (“Muscle Strength”), classified strength based on its expressions:

Neuromuscular-based expressions:

Maximum Strength
Maximum Dynamic Strength
Explosive Strength

Metabolic-based expressions:

Speed-Strength Endurance
Muscular Endurance

According to Bosco, the concept of a “strong subject” is incomplete without context. Strength must be defined based on the contraction type and whether its basis is neuromuscular or metabolic.

Understanding the different types of Strength

Maximum Strength
It is the ability to develop the force that allows lifting a maximum load that does not allow modulating the execution speed.

Training Load: 70%–100% of 1RM
Fiber Recruitment: All muscle fibers are recruited starting from ~70% load

Maximum Dynamic Strength
The ability to overcome submaximal resistance (<70% 1RM) with maximal acceleration.

Training Load: 30%–70% of 1RM

Explosive Strength
The capacity to generate high force in very short time intervals.

Training Load: 0%–30% of 1RM
Fiber Recruitment: Primarily fast-twitch fibers

Reactive Strength
It is the ability to absorb kinetic or potential energy due to running or a fall, returned by contracting the muscles due to the stretch reflex.

The Role of Time in Force Expression

Bosco’s field guidelines for power (force × velocity) have sometimes led to a skewed focus on strength, neglecting velocity. However, understanding the time required to produce force provides essential insight into the type of strength being trained.

How important is it to use time to understand which expression of strength should be used by monitoring the concentric action?

The following image analyzes the expressions of strength as a function of the duration of the concentric phase:

Maximum Strength: >700–800 ms
Explosive Strength: 200–400 ms
Maximum Dynamic Strength: 400–700 ms

Linking Strength Expression to Average Velocity

If we evaluate the expressed strength considering the average velocity:

In the case of maximum strength, we will have a load greater than 70% of the maximum and a velocity value less than 0.6 m/s.
In the case of maximum dynamic strength, a load between 40% and 70% and a velocity ranging from 0.6 to 1 m/s.
In the case of explosive strength, a load less than 40% of the maximum and a high execution velocity, greater than 1 m/s.

Linking Strength Expression to Average Velocity

Practical contribution of VBT technology

Given all this, how can GymAware RS and FLEX enhance training accuracy? Understanding the time it takes to produce force, rather than just the amount of load, is critical. Strength should not be confused with simply the weight on the bar.

Example:

Athlete A: Lifts 50 kg with 2 m/s² acceleration → Force = 1000 N
Athlete B: Lifts 100 kg with 1 m/s² acceleration → Force = 1000 N

Despite different loads, both athletes produce the same force. Technology like GymAware RS and FLEX capture both mass and acceleration, enabling coaches to understand total force (F = m × a). This allows for more nuanced and goal-specific training, not just based on heavy loads but on actual performance output.

Rethinking Traditional Strength Training: Insights from Vern Gambetta

Coach Vern Gambetta, the father of modern training, states:

“Stop and think for a minute – It takes approximately 8 seconds to express maximum strength. Most athletic movements occur in very short time intervals. So why do we spend such an inordinate amount of time emphasizing maximum strength? Is it because it’s measurable? Is it because it’s convenient? Is it a misunderstanding of the overload principle? Can you see the basic disconnect here? Isn’t it more important to develop the strength you can use? Think of strength training as coordination training with appropriate resistance to allow you to produce or reduce force in a time frame of 2 to 4 seconds. Training appropriate to the strength and power demands of the sport. Remember, too often what happens in the weight room stays in the weight room. Get out of the confines of the weight room walls and open up a completely new view to improve performance. Think athletic development not strength and conditioning. Build a robust athlete prepared for the demands of the sport.”

Conclusion

Modern athletic development must shift focus from simply lifting heavier to producing force efficiently and rapidly, in line with sport-specific demands. Tools like GymAware RS and FLEX help us rethink the way we train strength by adding the often-ignored variable: time. By doing so, we optimize training impact and move beyond the outdated notion that more weight alone equals improved performance.

Bibliography

Bosco C, La forza muscolare. Aspetti fisiologici ed applicazioni pratiche, Società Stampa Sportiva1997
Gambetta V, Athletic Development: The Art & Science of Functional Sports Conditioning, Human Kinetics Publishers, 2006
Azzone V, Cipriani M, Lucarini L, Allenamento della pesistica adattata agli sport di squadra, UniversItalia 2015