As a sprint specialist, I’m constantly studying how body mechanics influence athletic performance. Understanding an athlete’s unique structural attributes can help us develop training programs that enhance their natural strengths. One of the most influential yet often overlooked aspects is the Infrasternal Angle (ISA) – essentially, the angle of the lower ribs and sternum that shapes an athlete’s movement strategy. In this post, we'll explore the differences between Wide and Narrow ISA archetypes in sprinting and provide examples of professional athletes who embody these traits in football, track, and baseball.

The Basics: What is the Infrasternal Angle (ISA)?

The Infrasternal Angle (ISA) is a key structural characteristic that influences how an athlete moves. Typically, a Narrow ISA (less than 90 degrees) promotes a more elastic, bouncy movement pattern, while a Wide ISA (greater than 100 degrees) supports a more forceful, muscular approach to movement. However, ISA isn’t a black-and-white concept; it exists on a spectrum. Most athletes fall somewhere between narrow and wide, displaying characteristics of both, often adapting to the demands of their sport or daily activities.

Athletes may exhibit tendencies of a wide or narrow ISA depending on their biomechanics and training history. Not all "wides" or "narrows" present the same way; this is simply a comparison to help understand how ISA type may influence sprint style and optimal training strategies.

Narrow ISA Sprinters: Elastic, Bouncy, and Rhythmic

Narrow ISA athletes generally lean toward an elastic, spring-like movement quality. They tend to be bouncy and rhythmic in their stride, with efficient energy storage and release. Here’s a closer look at the key characteristics:

Elastic Sprint Style: These athletes naturally store and release energy with each stride, using elasticity to fuel a smooth, rhythmic run.
Swing Leg Window: Narrow ISA athletes often have a larger range of hip extension, enabling their swing leg to extend further behind. This creates a “wheel” effect with the legs, increasing stride length and efficiency.
Narrow Strike Path: Their foot strikes align closer to the centerline of the body, harnessing natural rotation and supporting smooth transitions between steps. This is advantageous in linear bounding and rhythm-based sprints.
Optimal Training: Narrow ISA athletes excel in tempo sprints and plyometrics, which build on their elastic and rotational abilities.

Examples of Narrow ISA Athletes:

Usain Bolt (Track)
Devonta Smith (Football)
Trea Turner (Baseball)

Wide ISA Sprinters: Muscular, Forceful, and Powerful

Wide ISA athletes often demonstrate a more muscular, force-driven approach to movement. They rely on strength and power, making them explosive over short distances and excelling in high-force outputs.

Muscular Sprint Style: Wide ISA athletes rely on muscular force for each stride, resulting in a compact, powerful sprinting style built for acceleration and short sprints.
Smaller Hip Extension Window: They typically have a more limited swing leg range, keeping strides compact and powerful. This enhances force output, particularly in the initial phases of a sprint.
Wider Strike Tracking: Their foot strikes are usually wider and more lateral, which aids in managing force absorption during multi-directional movements and lateral bounding.
Enhanced Exhalation Power: Wide ISA athletes tend to produce more thoracic pressure, which enhances stability during forceful lifting and acceleration.
Optimal Training: Wide ISA athletes benefit from strength-based lifts and short, high-intensity sprints that maximize power output.

Examples of Wide ISA Athletes:

Christian Coleman (Track)
Saquon Barkley (Football)
Mike Trout (Baseball)

ISA as a Spectrum: Embracing Individuality in Training

While it’s helpful to categorize athletes as "Wide" or "Narrow" ISA types, most athletes fall somewhere in between. ISA should be viewed as a spectrum where individuals exhibit a combination of elastic and forceful traits depending on their sport, body composition, and training history. Some Wide ISA athletes may show surprising elasticity, while certain Narrow ISA athletes could display powerful, forceful tendencies.

The demands of the sport and daily life influence how an athlete expresses their ISA type:

Football players are heavily influenced by the position they play, and what system they play in. Wides typically being your linemen, linebackers- narrows tend to be slot receivers, or kickers.
Track sprinters may express more Narrow or Wide tendencies depending on what their main event is. However, you will see both archetypes in shorter distance events.
Baseball players often adapt based on field position, with outfielders benefiting from elastic traits for running distances and infielders from muscular traits for rapid reaction.

Training strategies should therefore be customized to each athlete's unique blend of wide and narrow characteristics, enhancing their natural strengths rather than forcing them into a rigid category.

Training Takeaways: How to Program for Wide, Narrow, and In-Between ISA Athletes

Understanding an athlete’s ISA type can guide training decisions, allowing us to create programs that leverage their natural biomechanics. Here’s a general guide:

For Narrow ISA Athletes:

Focus on Elasticity and Rhythm: Emphasize plyometrics, rhythm drills, and tempo sprints to build on their elastic qualities.
Reinforce Linear Movements: Use linear bounding and coordination exercises that take advantage of their rotational strength and bounciness.
Light Strength Work: To avoid diminishing elasticity, keep strength training lighter and more dynamic.

For Wide ISA Athletes:

Build Strength and Power: Prioritize strength exercises like squats and deadlifts to capitalize on their forceful tendencies.
Use High-Intensity Sprints: Short sprints with long recovery periods enhance explosive power and maintain forceful sprinting mechanics.
Incorporate Lateral Work: Include lateral bounding and agility drills to support their natural stride width and lateral stability.

For Athletes in the Middle:

Blended Approach: Include a mix of plyometric and strength training to cover both elasticity and power.
Monitor Individual Responses: Athletes in the middle may respond differently to various exercises, so adjust training based on what optimizes their performance.
Focus on Sport-Specific Needs: Tailor drills to the specific demands of their sport, whether that requires more bounciness, strength, or agility.

Conclusion

In sprint training, acknowledging and respecting each athlete’s unique structural tendencies along the ISA spectrum can help unlock their full potential. Narrow ISA athletes thrive on elasticity and rhythm, while Wide ISA athletes excel with compact, powerful strides. Most athletes, however, land somewhere in between, blending these traits to suit the demands of their sport and training background. And remember, these are just examples of different archetypes I see in professional sports and with my athletes. The take home message is that athlete’s training should be biased to what their body type allows, but by no means should athletes completely avoid certain exercises because of their ISA.