Eccentric and Concentric Impulse: Key Metrics in Sport Performance

When an athlete performs a jump on a force plate, the movement can be divided into two key phases [although can be broken up into more phase]: the eccentric and concentric phases, each characterized by distinct muscular actions and force patterns. The eccentric phase involves the rapid lengthening of muscles as the body lowers, during which the force plate captures the braking forces applied to decelerate the body's descent. This phase is important for force generation and elastic energy storage. Following this, the concentric phase occurs as the muscles shorten explosively to propel the body upward, reflecting the force generated for takeoff.

Impulse, calculated as the integral of force over time during each phase, offers critical insight into the athlete’s neuromuscular performance and ability to generate power efficiently, helping optimize training and assess athletic readiness. Force plate technology enables precise quantification of these impulses, revealing how effectively an athlete transitions from braking to propulsion during a jump.

Impulse is fundamental in performance training because it directly relates to how effectively an athlete can apply force over a given period to produce movement. Unlike measuring peak force alone, impulse takes into account both the magnitude and duration of force application, providing a more comprehensive picture of an athlete’s explosive capabilities. In training, improving impulse can translate to enhanced jump height, sprint acceleration, and overall power output. By monitoring changes in eccentric and concentric impulse through force plate assessments, coaches can tailor training programs to target specific phases of force production, identify muscular imbalances, and track progress with precision. This detailed understanding allows for more individualized and effective training interventions that maximize athletic performance while minimizing injury risk.

Before diving into the specific roles of eccentric and concentric impulse during athletic performance, it's important to understand that these two phases contribute uniquely but complementarily to overall power production and efficiency. Eccentric impulse involves the controlled lengthening of muscles, which allows for storing elastic energy and preparing the muscles for explosive action. Meanwhile, concentric impulse reflects the force and time an athlete applies to propel themselves upward, which is critical for speed and jump height. Both impulses are integral to maximizing athletic output and reducing injury risk, making their targeted training vital for any performance program.

The assessment of athletic performance through force plates involves quantifying both concentric and eccentric impulses during various movement tasks, particularly countermovement jumps (CMJs). Understanding these two forms of impulse is critical for enhancing sports performance as they provide insights into the neuromuscular characteristics of athletes and their readiness for competition.

Concentric impulse refers to the force exerted during the shortening phase of a muscle contraction, which is vital for explosive movements like jumping. Studies have indicated that a successful concentric action results in a greater overall power output, which is critical in sports requiring explosive movements, such as basketball and volleyball (Amonette et al., 2023; , (Mayberry et al., 2018; . In contrast, eccentric impulse measures the force generated during the lengthening phase of the muscle contraction. Recognizing the importance of eccentric phases is increasingly emphasized in sports science as it can significantly impact performance metrics during explosive activities. Research has noted that eccentric peak force and overall eccentric performance are positively correlated with enhanced concentric outcomes, indicating that high levels of eccentric strength can yield more substantial concentric outputs (Cabarkapa et al., 2024; , Harper et al., 2020).

Importance of Eccentric Impulse

• Eccentric impulse occurs during muscle lengthening under load (e.g., landing or decelerating movements). It reflects how well an athlete can absorb and control forces.

• Eccentric strength (and impulse) acts like “brakes” for the body, allowing athletes to safely decelerate, create force during impact from landings or changes of direction, and minimize injury by managing high forces during these phases.

• Higher eccentric impulse capacity allows the athlete to handle larger forces safely, maintain better motor control during deceleration/braking, and optimize energy reuse for subsequent explosive actions.

Importance of Concentric Impulse

• Concentric impulse refers to the force produced by muscles while they are shortening (e.g., pushing off during a jump or sprint). It is calculated as the integral of force over time during the concentric phase.

• High concentric impulse, especially in a short timeframe like the first 100 ms, indicates an athlete’s ability to generate a large amount of force quickly, which correlates with explosive power and performance in movements such as jumping and weightlifting.

• An effective concentric impulse improves jump height, sprint acceleration, and changes of direction by producing rapid and high force output in the propulsive phase.

  
  

Overall Role in Sport Performance

• Force plates enable measurement of both eccentric and concentric impulses, giving insight into an athlete’s ability to generate and generate force at various phases of movement.

• Training programs targeting improvements in concentric impulse help develop explosive power, while those aimed at eccentric impulse enhance braking capacity and injury resilience.

• Understanding these impulses facilitates better athlete profiling, optimizing performance, and reducing risk of non-contact injuries in high-speed sports actions.

Recent findings suggest that enhancing both concentric and eccentric strengths through targeted training can improve an athlete's performance during competitive activities. Employing prescriptive training strategies tailored to an athlete’s force-time characteristics can optimize their training regimens, maximize the rate of force development (RFD), and thus improve jump heights and overall athletic performance (Guess et al., 2020; , Hart et al., 2019). A strong emphasis on balancing both concentric and eccentric training modalities may also contribute to long-term performance improvements and injury resilience, making them an integral part of athlete development programs across various sports (Amonette et al., 2023; , Merrigan et al., 2023).

In conclusion, the measurement of eccentric and concentric impulses via force plates is an invaluable tool in sports performance. Understanding the contributions of both types of impulses enables trainers and athletes to develop more effective training regimes that optimize athletic performance while simultaneously focusing on injury prevention.

The correct interpretation of these impulses also depends on technology such as force plates, which capture the comprehensive data necessary to analyze these dynamics accurately. For example, force plates can measure essential variables, including the eccentric rate of force development (ERFD) and concentric vertical impulse (CVI), providing a clearer picture of an athlete's physical capabilities (Mayberry et al., 2018; , Lake et al., 2018). This allows for the identification of specific strengths and weaknesses in an athlete's jumping mechanics, enabling tailored training interventions that could enhance both concentric and eccentric performance (Loturco et al., 2018; , Amasay & Suprak, 2022). Moreover, these insights have significant implications for injury prevention, as imbalances in eccentric and concentric strengths may predispose athletes to injuries such as ACL tears (Read et al., 2020).

References:

Amasay, T. and Suprak, D. (2022). Predicting time to take-off in a countermovement jump for maximal quickness from upright and squat starting positions. Journal of Human Kinetics, 84, 53-63.

Amonette, W., Vázquez, J., & Coleman, A. (2023). Cross-sectional analysis of ground reaction forces during jumps in professional baseball players. The Journal of Strength and Conditioning Research, 37(8), 1616-1622.

Cabarkapa, D., Čabarkapa, D., Philipp, N., & Fry, A. (2024). Competitive season-long changes in countermovement vertical jump force-time metrics in female volleyball players. The Journal of Strength and Conditioning Research, 38(2), e72-e77.

Guess, T., Gray, A., Willis, B., Guess, M., Sherman, S., Chapman, D., … & Mann, J. (2020). Force-time waveform shape reveals countermovement jump strategies of collegiate athletes. Sports, 8(12), 159.

Harper, D., Cohen, D., Carling, C., & Kiely, J. (2020). Can countermovement jump neuromuscular performance qualities differentiate maximal horizontal deceleration ability in team sport athletes?. Sports, 8(6), 76.

Hart, L., Cohen, D., Patterson, S., Springham, M., Reynolds, J., & Read, P. (2019). Previous injury is associated with heightened countermovement jump force‐time asymmetries in professional soccer players. Translational Sports Medicine, 2(5), 256-262.

Lake, J., Mundy, P., Comfort, P., McMahon, J., Suchomel, T., & Carden, P. (2018). Concurrent validity of a portable force plate using vertical jump force–time characteristics. Journal of Applied Biomechanics, 34(5), 410-413.

Loturco, I., Pereira, L., Kobal, R., Abad, C., Fernandes, V., Ramírez‐Campillo, R., … & Suchomel, T. (2018). Portable force plates: a viable and practical alternative to rapidly and accurately monitor elite sprint performance. Sports, 6(3), 61.

Mayberry, J., Patterson, B., & Wagner, P. (2018). Improving vertical jump profiles through prescribed movement plans. The Journal of Strength and Conditioning Research, 32(6), 1619-1626.

Merrigan, J., Strang, A., Eckerle, J., Mackowski, N., Hierholzer, K., Ray, N., … & Briggs, R. (2023). Countermovement jump force-time curve analyses: reliability and comparability across force plate systems. The Journal of Strength and Conditioning Research, 38(1), 30-37.

Read, P., Auliffe, S., Wilson, M., & Graham‐Smith, P. (2020). Lower limb kinetic asymmetries in professional soccer players with and without anterior cruciate ligament reconstruction: nine months is not enough time to restore “functional” symmetry or return to performance. The American Journal of Sports Medicine, 48(6), 1365-1373.