In episode 155 of the CSP Elite Baseball Development Podcast, Eric Cressey interviews Rick Franzblau, Assistant Athletic Director and Director of Olympic Sport Strength and Conditioning at Clemson University, on the subject of individualized training through the lens of the infrasternal angle (ISA). By using the ISA to assess an athlete’s structural and functional tendencies, coaches can tailor programs to enhance performance and minimize injury risk.

This blog post explores the ISA and how it impacts pitchers' movement and arm slot as well has its various implications for hitters. It also provides specific training adaptations for narrow and wide ISA athletes, including both hitters and pitchers.

Understanding the Infrasternal Angle (ISA)

The infrasternal angle (ISA) is the angle formed at the lower end of the ribcage where the ribs meet at the xiphoid process of the sternum. This angle can be narrow (less than 90 degrees) or wide (greater than 90 degrees), and it reflects the structural positioning of the ribcage and the mechanics of an athlete’s breathing and movement. Typically, athletes fall into one of these two categories, and knowing their ISA helps to determine their body’s bias toward certain types of movements.

To measure the ISA, coaches or clinicians palpate the lower rib cage while the athlete is relaxed. A narrow ISA suggests a more compressed ribcage laterally, while a wide ISA indicates a broader, more expansive orientation. This structural difference has several implications, influencing flexion, extension, lateral flexion, and rotation of the ribcage and spine.

How ISA Impacts Movement

The ISA fundamentally affects movement because it influences how the thoracic ribcage and spine flex, extend, rotate, and stabilize. In narrow ISA individuals, the ribcage is biased toward external rotation (ER), favouring movements that require rapid rotation and elastic recoil. In wide ISA individuals, the ribcage is positioned with a more significant internal rotation (IR) window, suiting them for compression-based strength exercises and sustained force production over wider ranges of motion.

• Flexion and Extension: Narrow ISA athletes are more efficient with rotation and prefer movements that require an upright posture. Wide ISA athletes, with their expansive ribcage, are better suited for flexion-based, compressive movements, excelling in exercises that involve sustained force production over longer ranges of motion.

• Lateral Flexion and Rotation: Narrow ISA athletes, due to their smaller IR windows, are optimized for rotational power over lateral bending. Wide ISAs, with their larger IR capacity, perform well in movements involving lateral flexion, allowing them to generate force through extended movement arcs.

• Arm Slot for Pitchers: Narrow ISA pitchers, with their rotational preference and upright posture, are best suited for a lower arm slot. This allows them to leverage rotation of the ribcage without requiring excessive lateral flexion, which their structure limits. In contrast, wide ISA pitchers can achieve a higher arm slot thanks to their capacity for lateral flexion and extension, allowing them to create force through more extensive ranges of motion.

Training Strategies for Narrow vs. Wide ISA Athletes

Armed with an understanding of ISA, coaches can design individualized training programs that align with each athlete’s strengths and avoid unnecessary strain. Narrow ISAs excel in high-speed, rotational exercises, while wide ISAs thrive in grind-based, compressive movements. These principles apply to both hitters and pitchers, optimizing performance across a variety of movement types. That is not to say, however, that narrow ISA athletes should avoid high compression-based movements. Rather, their ISA and various skill-specific key performance indicators (KPIs) should be monitored closely to know when it is time to adjust programming back to exercises which are more aligned with their anatomical structure and motor preferences.

Narrow ISA Athletes: Elastic and Rotational Focus

Narrow ISA athletes are expansive, with an external rotation (ER) bias that enhances their rotational power and elasticity. They excel in short, high-speed movements, ideal for both explosive swings and pitching mechanics that rely on quick force generation.

Training recommendations for narrow ISA athletes:

• Elastic, Rotation-Based Training: Narrow athletes benefit from exercises that emphasize rotational power and speed. This approach allows narrow ISA pitchers and hitters to enhance elasticity and force production over shorter ranges of motion.

• Large, Preparatory Loading Patterns: Narrow hitters can often benefit from high hand placement to create a more substantial load-up phase before swinging. For pitchers, a more extended, rotational wind-up optimizes the elastic energy of their throw without straining lateral flexion.

• Single-Leg or Front-Leg Loading: Narrow hitters often favour a single-leg dominant, front-leg load for maximum control and power generation. Similarly, narrow ISA pitchers benefit from exercises emphasizing lead leg stabilization, supporting a controlled, efficient follow-through.

• Avoiding Heavy, Grind-Based Exercises: Compressing narrow athletes with heavy, grind-based exercises (heavy squats & hinges) can limit their rotational capabilities. Lighter, faster lifts help maintain their elastic power and prevent overuse injuries, preserving their movement quality.

Wide ISA Athletes: Power and Compression Focus

Wide ISA athletes, with their more significant internal rotation (IR) window, excel in compressive strength and are suited for heavy, grind-oriented exercises. This trait benefits hitters by providing stability in a balanced stance, while pitchers can leverage this stability for higher arm slots.

Training recommendations for wide ISA athletes:

• Strength-Based, Grind-Oriented Movements: Wide ISAs handle higher resistance well, thriving with heavy, compressive exercises such as squats and deadlifts.

• Symmetrical or Double-Leg Loading: Wide hitters excel in balanced stances with closer to 50/50 weight distribution between their lead and trail sides, allowing even load distribution to maximize compressive power. For wide ISA pitchers, symmetrical loading aids stability and reduces over-rotation, improving control on the mound.

• Lower Hand Placement in Batting: Wide hitters benefit from a lower hand setup, which allows them to initiate the load phase quickly and powerfully. For pitchers, a more compact arm path supported by a higher arm slot can improve control and aid in force production.

• Effective Hinge Movements: Wide ISAs naturally gravitate toward hinge-based movements, pressurizing effectively without overloading the spine. For pitchers, this hinge preference supports deeper hinging into the trail leg during the initiation of their stride.

Integrating ISA Knowledge with Real-Time Adaptation

An ISA-informed approach requires constant adaptation. Coaches should continually assess each athlete’s performance through film analysis, motion capture, and metrics such as bat speed, exit velocity, and pitch velocity. For instance, if a narrow ISA athlete starts losing rotational power due to excessive compression from heavy lifting, coaches can pivot to lighter, faster movements to restore balance and prevent injury.

This is why implementing a frequent and ongoing assessment system enables trainers and coaches to create dynamic, responsive programs that evolve with each athlete’s progress. For pitchers, ISA assessments guide adjustments to optimize arm slots, ensure longevity, and maintain velocity throughout the season. For hitters, a similar approach preserves power and adaptability, helping players sustain high performance at the plate.

Bringing ISA-Based Training to the Field

The CSP Elite Baseball Development Podcast episode with Rick Franzblau sheds light on how the infrasternal angle (ISA) can be invaluable in baseball training, offering insights into tailored strategies for hitters and pitchers. By understanding an athlete’s unique ISA and applying it to training, coaches can create programs that harness each athlete’s structural advantages, whether through rotational power, compressive strength, or stability. For both pitchers and hitters, this individualized approach unlocks new potential while protecting against injuries, allowing athletes to train in ways that suit their natural movement tendencies.

To learn more about how ISA can transform individualized training in baseball, check out Rick Franzblau’s conversation with Eric Cressey on episode 155 of the CSP Elite Baseball Development Podcast.