2019 ISAKOS Biennial Congress ePoster #753
Influences of Muscle Fatigue of Unilateral Lower Extremity on Jump-Landing
Satoshi Imai, PT, MSc, Tokyo JAPAN
Kengo Harato, MD, PhD, Tokyo JAPAN
Yutaro Morishige, MD, Tokyo JAPAN
Takeo Nagura, MD, PhD, Tokyo JAPAN
Ryoji Hayakawa, MEng, Tokyo JAPAN
Shu Kobayashi, MD, PhD, Tokyo JAPAN
Yasuo Niki, MD, PhD, Tokyo JAPAN
Morio Matsumoto, MD, PhD, Tokyo JAPAN
Masaya Nakamura, MD, PhD, Tokyo JAPAN
Toshiro Otani, MD, PhD, Tokyo JAPAN
Hideo Matsumoto, MD, PhD, Tokyo JAPAN
Institute for Sports Medicine, School of Medicine, Keio University, Tokyo, JAPAN
FDA Status Not Applicable
Risk of anterior cruciate ligament injury is increased by muscle fatigue of unilateral lower extremity on jump-landing
Leg fatigue is one of the risk factors for non-contact anterior cruciate ligament (ACL) injury. In addition, asymmetry of the lower leg function may also induce the ACL injury. In this study, effect of unilateral leg fatigue on jump-landing was analyzed in order to seek risk factor of ACL injury.
Twenty female college students (mean age; 20.2 ± 1.3 years) were involved in this study. This study was approved by Medical Research Ethics Committees of our University. Participants were asked to perform “drop vertical jump (DVJ)”, from a 30-cm high box to a distance of 25% of their height away from the box, before- and immediately after-fatigue protocol. It was repeated after taking rest for 2 minutes thereafter. The fatigue protocol was that a subject performs repeated single leg stand-up from 30-cm high chair until she fails to continue to do it because of fatigue. Jumping height, maximum vertical ground reaction force (vGRF), and knee joint angles and moments during DVJ were analyzed by using 3-dimentional motion analysis system with 8 cameras and 46 retroreflective markers (Oqus, Qualisys, Savedalen, SWEDEN), Visual 3D software (C-Motion, USA), and force platforms (Type AM6110, Bertec, Columbus, OH, USA). All data were expressed as mean ± standard error. Differences in each parameter was analyzed using ANOVA with post hoc test. Statistical significance was set at P < .05.
In fatigue protocol, number of stand-up exercise until fatigue was 45±25 repetitions. Jumping height was slightly decreased after-fatigue protocol. On the fatigue side, vGRF was significantly decreased (819±263 N/kg) with respect to that before-fatigue protocol (1318±394N/kg). Maximum knee extension moment in fatigue side was also significantly decreased (1.47±0.50 N-m/kg) with respect to that before-fatigue protocol (2.06±0.60 N-m/kg). On the non-fatigue side, no significant differences were observed both in vGRF and in maximum knee extension moment. However, flexion angle at peak vGRF was significantly decrease (42.1±7.0 degree) with respect to that before-fatigue (47.1±4.9 degree), and knee extension moment within 40 ms from initial contact was significantly increased. Jumping height was recovered to before-fatigue level after 2 minute rest. No significant difference was observed in fatigue side vGRF (896±268 N/kg) with respect to that immediately after-fatigue protocol. Flexion angles of both knees at initial contact were decreased after the rest.
It is obvious that the performance of the lower extremity is affected by fatigue. However, the noteworthy finding in this study is that the biomechanics of the non-fatigue side is also affected by fatigue of the contra-lateral side, such as decrease in flexion angle and increase in extension moment while landing. In addition, although the performance (jumping height) was recovered after having rest, changes in the biomechanics were still remained at the level after fatigue protocol. These biomechanical changes are thought to be the risk factors for ACL injury, and they can be useful information to understand the mechanism of contra-lateral side of ACL injury after the ACL reconstruction.