Improving athletic performance with muscle mechanical properties

Improving athletic performance with muscle mechanical properties

Recent advances in ultrasound technology are improving the understanding of muscle mechanics. Credit: Associate Professor Ryoichi Ema of Shizuoka Sangyo University

For any athlete, be it a marathon runner or a volleyball player, improving one’s performance is critical. In fact, a major area of ​​research in sports science is dedicated to understanding how various muscle factors – size, weight, and height, affect an athlete’s dynamic performance. Muscle characteristics in the passive or “relaxed” state, including muscle tone, stiffness, and rigidity, are of particular interest. While some studies suggest a possible association between negative muscle characteristics and performance during rigorous exercise, other studies report no association. As a result, current evidence linking passive muscle mechanical properties to performance is inconsistent and inconclusive.

Given the need to improve understanding in this area, Dr. Ryoichi Ema, Assistant Professor at Shizuoka Sangyo University in Japan, investigated the relationship between passive muscle mechanical properties and dynamic performance. Citing the rationale behind the study, Dr. Emma says that “shear modulus or muscle stiffness is an indicator of passive muscle mechanical properties. The vastus lateralis (VL) is an important thigh muscle associated with intense leg extension exercises. Therefore, our research focused on examining whether The shear modulus of VL correlates with the dynamic performance outcomes of high-speed activities. With this study, we aim to bridge inconsistencies in previous findings.” The study was made available online at European Journal of Sports Science.

Dr. Emma hypothesized that the mechanical properties of relaxed muscles are related to performance during a high-speed stretch-shortening cycle (SSC) and explosive exercises. He and his team recruited 30 healthy young women (18 physically active and 12 sedentary), who were randomly asked to perform different exercises involving VL. These included the squat jump (SJ), counter jump (CMJ), bounce jump (RJ), and the three-speed multi-joint leg extension (low, medium, and high). The team measured jumping heights for the jumping exercises and muscle strength for the leg extension exercise. Combined with the evaluation of the comfortable shear modulus of the VL using ultrasound elasticity planning. Finally, they determined the association between these variables through statistical analysis.

The results showed that the shear modulus of VL was positively correlated with the activity-based parameters. The association was more significant with RJ height, and the strength of multi-joint leg extension at medium and high speeds. Conversely, the association was non-significant with higher SJ and CMJ and lower speed leg extension strength. This indicates that passive mechanical muscle properties, such as the shear modulus, are essential for performance during a series of rapid SSC exercises. Likewise, it indicates that the mechanical properties of passive muscles are essential for the generation of potential force at high speeds.

But what is the underlying physiology and the significance of these connections? Muscles that have an abundance of connective tissue and contractile elements tend to have a higher negative shear modulus. This allows for a quick transfer of force to the tendons and a better balance between force and speed, which helps in modulating the speed of movement. SSC movements and multi-joint leg extensions are usually observed at higher speeds in fast activities such as running, jogging and volleyball. Therefore, these results indicate that the negative mechanical properties of the agonist (contractor) muscle, such as the VL, play an important role in performance during high-speed dynamic exercises/activities. Furthermore, this study rolled the ball for future research to look at the combined role of other muscle groups and muscle factors in dynamic performance.

By discussing the real-world applications of these findings, Dr. Emma that “these findings could be useful for guiding athletic training and coaching, and for developing appropriate exercise techniques for individuals aiming to improve performance.”


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more information:
Ryoichi Ema, The Association Between Elastic Imaging-Assured Muscle Mechanical Properties and High Speed ​​Dynamic Performance, European Journal of Sports Science (2022). DOI: 10.1080 / 17461391.2022.2097129

Presented by Shizuoka Sangyū University

the quote: Muscle Mechanics: Improving Athletic Performance with Muscle Mechanical Properties (2022, August 3) Retrieved September 20, 2022 from https://medicalxpress.com/news/2022-08-muscle-mechanics-sports-mechanical-properties.html

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