Unlocking Speed: The Benefits of the Clark 105 Exercise for Sprint Performance
Discover the power of the Clark 105 Exercise, inspired by the research of Dr. Ken Clark, PhD, who identified the critical role of the thigh split angle in sprinting performance. Introduced to this groundbreaking concept by Chris Korfist, a leading Chicago speed coach, I developed this isometric training method to enhance top-end speed, acceleration, and running mechanics. By strengthening the muscles that control peak thigh split positions—especially the glutes and hip flexors—athletes can achieve faster, more efficient strides while reducing injury risks. Ideal for both youth and elite athletes, the Clark 105 is a safe, effective solution for improving sprint performance.
Understanding the Thigh Split and Its Importance
The thigh split refers to the angle between the thighs during the early flight phase of a sprint—when one thigh reaches peak extension while the other reaches peak flexion. Essentially, it represents the total range of motion (ROM) that the thighs cover during the swing phase of a running stride.
Achieving an optimal thigh split is crucial, but an even more critical determinant of top sprinting performance is the ability to reverse the movement at the peak split position. This is often described as the capacity to “block at the top”—rapidly accelerating the thighs back in the opposite direction with high angular force. This reversal generates the momentum required for maximum speed and stride efficiency.
Typical values of the thigh split vary based on athletic specialization:
- Track and field athletes: ~100 to 105 degrees (range: 95-115 degrees)
- Team sport athletes: ~95 to 100 degrees (range: 85-110 degrees)
Several factors influence an athlete’s ability to achieve and maintain an effective thigh split, including:
- Strength and mobility in the hip flexors, glutes, and other related muscles.
- Sprint movement patterns, influenced by neuromuscular coordination.
- Control strategies, such as the vertical force applied during ground contact.
Introducing the Clark 105 Exercise
To address these critical performance factors, I developed the Clark 105 Exercise—an isometric drill that places athletes in a greater-than-105-degree thigh split position and requires them to hold this stance under maximum muscular tension. This position replicates the demands of sprinting by activating the same muscles involved in high-speed running, such as the glutes and hip flexors.
Clark 105 Torque Isometric Overcoming
How the Clark 105 Improves Performance
Research and training experience have shown that strength in the peak thigh split position has a significant impact on several key aspects of athletic performance:
- Top-end speed: Strengthening this position enhances an athlete’s ability to maintain efficient strides at high velocity.
- Acceleration: Athletes develop better control during rapid changes in direction and short-burst sprints, improving overall explosiveness.
- Running mechanics: The exercise helps athletes achieve better hip extension and flexion, leading to more powerful and efficient strides.
- Safety and injury prevention: By training isometrically, athletes strengthen stabilizing muscles, reducing the risk of strains and imbalances.
How to Perform the Clark 105
The Clark 105 can be executed in various ways to target different aspects of strength and motor control:
- Basic Isometric Hold: Athletes hold a greater-than-105-degree thigh split for 5 to 10 seconds per side, with maximum muscular effort. Repeating this hold for 3 to 6 sets per session has yielded significant results.
- Dynamic Pulsing Variation: Athletes turn their muscles on and off quickly—maximally contracting for less than a second, relaxing, and then contracting again—for a duration of up to 10 seconds. This variation enhances the neuromuscular system’s ability to generate rapid force.
- Rotational Core Activation: Athletes twist their upper bodies during the hold, adding an element of core stability training. This helps improve coordination and control during dynamic movements.
- Torque Generation: In some variations, athletes squeeze their legs inward to create additional torque, strengthening hip and thigh stabilizers.
Why the Clark 105 Is Safe and Effective for All Athletes
One of the greatest benefits of the Clark 105 Exercise is its safety, particularly for youth athletes. Since the exercise is isometric, it places minimal joint stress while still delivering high-intensity muscle activation. The controlled nature of the movement ensures that athletes can safely build strength without overloading their bodies.
Transform Your Sprinting with the Clark 105
Athletes who incorporate the Clark 105 into their training routines have reported dramatic improvements in both speed and strength. By targeting the critical thigh split position, this exercise enhances performance across sprinting phases—from initial acceleration to sustained top speed. Whether you’re a sprinter aiming for a new personal best or a team sport athlete looking to improve agility, the Clark 105 is a powerful addition to any training program
A List alternatives and variations of the exercise
Clark, K. P., Meng, C. R., & Stearne, D. J. (2020). ‘Whip from the hip’: Thigh angular motion, ground contact mechanics, and running speed. Biology Open, 9(10), bio053546. https://doi.org/10.1242/bio.053546
Murphy, A., Clark, K. P., Murray, N., Melton, B., Mann, R., & Rieger, R. (2021). Relationship between anthropometric and kinematic measures to practice velocity in elite American 100 m sprinters. Journal of Clinical and Translational Research, 7(5), 682. https://doi.org/10.xxxx
Alt, T., Komnik, I., Ryan, L. J., & Clark, K. P. (2024). Top speed sprinting: Thigh angular motion and eccentric hamstring strength in faster vs. slower sprinters. Human Movement Science, 98, 103280. https://doi.org/10.1016/j.humov.2024.103280
