Author(s): TAKAHASHI, H., YAMAZAKI, Y., KATO, R., YAMAMOTO, K., YANAGIYA, T., Institution: JUNTENDO UNIVERSITY, Country: JAPAN, Abstract-ID: 1946

INTRODUCTION:
Maximal strength has been reported to improve running economy and is considered an important factor influencing long-distance running performance [1]. Muscle strength is closely associated with morphological characteristics, and maximal strength is generally proportional to muscle cross-sectional area (CSA), which is often used as an indicator of muscle strength. Previous studies have reported positive associations between quadriceps femoris CSA and sprint performance in long-distance runners [2].
However, increased muscle mass may increase lower-limb mass and moment of inertia, potentially disadvantaging leg swing during running. Although muscle morphology is thought to influence running kinematics and performance, the relationship between thigh muscle CSA and running kinematics remains unclear. Therefore, the purpose of this study was to investigate the relationship between the CSA of individual thigh muscles and lower-limb kinematics in long-distance runners.
METHODS:
Eight male long-distance runners participated in this study (height: 1.66 ± 0.05 m, weight: 53.6 ± 4.5 kg, 5000-m personal best time: 14’11’’0 ± 0’28’’2). CSA of each muscle was obtained from T1-weighted spin-echo axial images at 50% of the right thigh length using magnetic resonance imaging. Running kinematics were obtained by recording treadmill running at 20 km/h from the left sagittal plane. Joint angles, angular velocities, and joint torques of the hip and knee were calculated from digitized body landmark coordinates. Pearson's correlation coefficients were used to analyze relationships between muscle CSA and 5000-m personal best times, kinematic variables, and joint torques.
RESULTS:
CSA in rectus femoris exhibited significant positive correlations with mean hip extension angular velocity (r=0.92, p<0.01) and maximum knee flexion torque during the flight phase (r=0.80, p<0.05). In contrast, CSA in semimembranosus exhibited a significant negative correlation with mean knee flexion angular velocity (r=-0.84, p<0.05). No significant correlations were observed between CSAs in other muscle and 5000-m personal best times, kinematic variables, or joint torques.
CONCLUSION:
In long-distance runners, morphological characteristics of the rectus femoris and semimembranosus are associated with hip and knee joint angular velocities during running and knee joint torque during the flight phase.
1. Støren et al., Med Sci Sports Exerc, 2008.
2. Ando et al., J Hum Kinet, 2022.