In this article, I aim to address misconceptions regarding the mechanical characteristics of acceleration in sprinting. We will analyze concrete data based on measurements from force platforms, which are considered the gold standard in biomechanics. By comparing three different types of exercises, we can better understand how ground reaction forces affect acceleration and sprinting performance.

Analysis of Force Data in Different Exercises

To begin with, let’s examine data collected from three types of exercises: one involving high acceleration (maximum sprint start), one involving low acceleration (jogging start), and one without displacement (stationary jumps). These data will allow us to observe variations in ground reaction force components in each case.

High Acceleration: Maximum Sprint Start

During a maximum sprint start, two main components of ground reaction force in the sagittal plane are observed:

• Vertical Component: This force is directed upwards and includes body weight and gravity.
• Horizontal Anteroposterior Component: This force is directed forwards and backwards.

In this exercise, the vertical force reaches over 1100 Newtons, indicating significant vertical propulsion. While the magnitude of the horizontal impulse is lower, it is crucial for forward acceleration.

During the first three steps, the average acceleration of the center of mass was 3.9 m/s², reaching a final velocity of 2.12 m/s. Despite the greater vertical force due to body weight and gravity, forward movement is primarily driven by horizontal force.

Detailed Data from Maximum Sprint Start:

• Maximum Vertical Force: >1100 Newtons
• Vertical Impulse: Significant
• Average Horizontal Force: Lower compared to vertical force
• Proportion of Horizontal Force: 24% of ground reaction force
• Average Center of Mass Acceleration: 3.9 m/s²
• Final Velocity after three steps: 2.12 m/s

Low Acceleration: Jogging Start

During a jogging start, the final velocity after three steps is 1.5 m/s, with significantly lower average acceleration. The proportion of horizontal force is also lower, indicating more vertically oriented propulsion.

Despite having similar or even higher vertical force and vertical impulse compared to the high-acceleration sprint, performance is lower due to reduced horizontal force. This demonstrates that the direction of force application, not just its magnitude, is critical.

Detailed Data from Jogging Start:

• Final Velocity after three steps: 1.5 m/s
• Average Center of Mass Acceleration: Much lower than maximum sprint start
• Proportion of Horizontal Force: Lower, more vertical push
• Horizontal Force: Much lower than maximum sprint start
• Horizontal Impulse: Much lower than maximum sprint start
• Average Vertical Force: Similar or even higher than maximum sprint start
• Vertical Impulse: Similar or even higher than maximum sprint start

Stationary Jumps: No Displacement

During stationary jumps, no forward velocity or acceleration is generated. Data shows that the average horizontal force is practically zero, while the vertical component is extremely high. This exercise produces the highest vertical ground reaction force component but does not result in forward movement.

This underscores that the magnitude of vertical force does not determine its importance for acceleration tasks. The lack of horizontal force explains the absence of forward displacement.

Detailed Data from Stationary Jumps:

• Final Velocity: 0 m/s
• Acceleration: 0 m/s²
• Average Horizontal Force: Practically zero
• Vertical Force: Extremely high, highest among the three exercises
• Vertical Impulse: High, but lower than other exercises due to shorter contact time

Magnitude vs. Importance of Force

It is crucial not to confuse the magnitude of force with its importance for a specific task. In the context of sprinting acceleration, horizontal force is far more relevant than vertical force because it propels forward movement.

Extreme Example: Jumping Backwards

To illustrate this point, consider an extreme example: jumping backwards. Here, despite a high vertical force component, the horizontal component is negative, causing backward movement. This example highlights the crucial role of force direction in determining the type of movement generated.

Analogy in Team Sports

In team sports like soccer, players walk 80% of the time. Despite the high volume of walking, this does not necessarily correlate with key performance indicators. What matters in these sports are acceleration and speed, not the amount of walking. Therefore, the focus should be on sprint and high-speed training rather than walking.

• Walking Volume: High, 80% of the time
• Importance for Performance: Low
• Key Performance Indicators: Acceleration and speed

Conclusion

In summary, while the magnitude of the vertical force component may be high, it should not be confused with its importance for acceleration tasks. Horizontal force is key to enhancing sprinting performance. This analysis underscores the importance of focusing on applying horizontal force to maximize acceleration and sprinting performance.

I hope this information has been helpful in clarifying misconceptions about sprinting acceleration. Remember to always focus on what truly matters for each specific task!

Thank you for reading, and until next time!