Effects of Running Exercises on Mechanical Properties in Vastus Lateralis Muscle Tendon Complex

Abstract

Introduction: Vastus lateralis muscle (VL) works to stabilize knee joint during foot contact¹⁾. Muscle tendon complex stiffness decreases with fatigue²⁾. If the stiffness of VL tendon structure becomes lower during running, it may affect running performances. This study is aimed to clarify the effect of acute running on vastus lateralis muscle-tendon stiffness.

Methods: Four young male participants (22.8±1.0 yrs, 1.73±0.05 m, 62.8±5.4 kg) performed maximal voluntary isometric knee extensions for three times before, immediately after and 30 min after the run. Subjects ran for 30 minutes on a treadmill with 5 min/km running pace. A real-time ultrasonic apparatus (SSD-4000, Aloka) was used to obtain longitudinal ultrasonic images of VL during torque measurements. From the ultrasonic images, we measured the lengthening of tendon structure. We calculated aponeurosis stiffness and hysteresis from the relations between force and lengthening³⁾.

Results: Both maximal voluntary isometric knee extension strength and lengthening of VL aponeurosis were not significantly different between pre-run measurement and immediate measurements. Stiffness of VL tendon structure increased and VL tendon hysteresis decreased immediately after running. But they did not significantly change. And they returned to the same value as before the run after 30 minutes.

Conclusion: Stiffness of VL tendon structure tended to increase immediately after 5 minutes/km running for 30 minutes. But after 30 minutes it returned to the same value as before the run. We think that the pace and time of this study are not high intensity enough to change.