The stiffness of muscle–tendon units and of tendons in the lower legs plays important roles in sprinting and long-distance running. However, the association of muscle stiffness with sprinting and running remains unknown. This study aimed to identify the characteristics of muscle stiffness in sprinters and long-distance runners, and to determine how muscle stiffness is related to the performance of these athletes.
In 22 male sprinters (SPR group), 22 male long-distance runners (LDR group), and 19 healthy untrained control male subjects (CON group), the muscle shear wave speed (a proxy for stiffness) of the vastus lateralis (VL) was measured under passive (resting) and active (contracting the knee extensors at 50% of maximal voluntary contraction) conditions, by using ultrasound shear wave elastography.
The passive VL shear wave speed in SPR group was significantly lower than that in LDR group (P = 0.039). The active VL shear wave speed in LDR group was significantly higher than that in SPR (P = 0.022) and CON (P < 0.001) groups. In SPR group, the 100-m race time was negatively correlated to the passive VL shear wave speed (r = −0.483, P = 0.023) and positively correlated to the active VL shear wave speed (r = 0.522, P = 0.013). In the LDR group, the 5000-m race time was positively correlated to the passive VL shear wave speed (r = 0.438, P = 0.047) but not to the active VL shear wave speed.
The muscles of sprinters and long-distance runners exhibit characteristic stiffness that can be beneficial to their athletic performance. Passive and active muscle stiffness may play different roles in human locomotion, depending on locomotion speeds.
1Graduate School of Health and Sports Science, Juntendo University, Chiba, JAPAN
2Department of Sports and Life Sciences, National Institute of Fitness and Sports in Kanoya, Kanoya, JAPAN
3Japan Society for the Promotion of Science, Tokyo, JAPAN
4Graduate School of Engineering and Science, Shibaura Institute of Technology, Saitama, JAPAN
5Faculty of Sport and Health Science, Ritsumeikan University, JAPAN
Address for correspondence: Naokazu Miyamoto, Ph.D., Graduate School of Health and Sports Science, Juntendo University 1-1 Hiraka-gakuendai, Inzai, Chiba 270-1695, Japan; E-mail: firstname.lastname@example.org.
Submitted for publication December 2018.
Accepted for publication April 2019.
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Online date: May 4, 2019