Key Findings from New Insights into Sprint Biomechanics and Determinants of Elite 100m Performance (Morin, Edouard, and Samozino).

This research paper examines the biomechanics of sprint running and how these factors affect performance in the 100m race. The study explores the importance of ground reaction force (GRF), particularly its horizontal component, in determining acceleration. The authors used a motorised instrumented treadmill to measure GRF in detail and found that the ability to orient GRF forward is crucial for sprint performance, even more so than the total force produced. The study also investigates how different levels of athletes, ranging from non-specialists to world-class performers, apply force differently during sprinting. The results highlight the need for training programs that focus on both physical strength and technical skill development, specifically in orienting force forward during acceleration.

The force application technique employed by sprinters during the acceleration phase plays a pivotal role in their overall performance. While the capacity to generate a high amount of force is essential, the ability to effectively apply and orient this force in a forward direction is more critical for optimal sprint performance.

The relationship between force application and sprint performance can be understood through the concept of 'Ratio of Forces' (RF). RF is the ratio of the average horizontal force (FHzt) to the resultant ground reaction force (FTot) during the contact phase of a stride.

• A higher RF indicates that a greater proportion of the total force generated is directed horizontally, contributing to forward propulsion.

As sprinters accelerate, their body naturally transitions towards a more upright position, leading to a decrease in RF.

The rate at which this decrease in RF occurs with increasing speed is captured by the 'Decrement in RF' (DRF) index. A higher DRF value indicates that the sprinter is better able to maintain a high RF despite increasing velocity, signifying superior force application technique.

Studies using an instrumented treadmill, capable of measuring both horizontal and vertical components of ground reaction force, have provided valuable insights into the significance of force application technique. Research involving non-specialists, national-level sprinters, and a world-class sprinter highlighted a strong correlation between DRF and sprint performance in a 100m sprint.

The world-class sprinter, despite not exhibiting exceptionally high total force production, demonstrated a superior ability to direct the force horizontally, as evidenced by a remarkably higher DRF compared to national-level sprinters and non-specialists. This difference in force application technique, rather than total force output, was a key factor contributing to his superior performance.

Training Applications

The findings from these studies have significant implications for the training and development of sprinters.

It suggests that training regimens should not solely focus on maximising force production but should equally emphasize developing the skill of effectively applying this force in a forward direction. The focus should shift from simply increasing the 'amount' of force to improving the 'way' force is applied onto the ground. This could involve incorporating exercises that specifically target hip extensor muscles (gluteus and hamstrings) and ankle stabiliser muscles, enhancing their role in backward propulsion and force transmission to the ground, especially at higher running velocities.

Hip Extensor Exercises

• Deadlifts: Focus on conventional and single-leg deadlifts to strengthen the gluteus maximus and hamstrings, promoting effective hip extension.

• Hip Thrusts: These isolate and activate the glutes, enhancing their ability to generate horizontal force.

• Bridges: A variation of hip thrusts that can also be performed unilaterally to address imbalances.

Ankle Stabliser Muscles

• Ankle Mobility Drills: Use dynamic stretches to improve dorsiflexion and plantarflexion range of motion, which supports effective force application during sprints.

• Single-leg Balance Exercises: Incorporate balance boards or stability discs to enhance proprioception and ankle stabilisation.

Resisted Sprints

• Resisted Acceleration Drill: Use resistance bands or partner assistance to focus on applying horizontal force in a controlled manner.

• Hill Sprints: Running uphill increases the demand for horizontal force application and strengthens the muscles involved in acceleration.

• Sled Pulls: Attach a sled or resistance harness to create resistance during sprints, forcing the athlete to apply greater horizontal force.

Plyometric Drills

• Bounding: This exercise mimics sprinting mechanics and encourages a powerful push-off while maintaining horizontal force application.

• Box Jumps: Focus on explosive upward force while emphasising forward momentum during landing.