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E-06 Thematic Poster - Jumping and Landing Friday, May 31, 2019, 9: 30 AM - 11: 30 AM Room: CC-101B

Static Loading of the Knee Joint Results in Modified Single Leg Landing Biomechanics

2242 Board #7 May 31 9:30 AM - 11:30 AM

Olson, Michael W. FACSM

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Medicine & Science in Sports & Exercise: June 2019 - Volume 51 - Issue 6S - p 612-613
doi: 10.1249/01.mss.0000562331.77983.20
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PURPOSE: The purpose of this study was to examine the mechanical and neuromuscular responses to single leg drop landing perturbations before and after passive loading of the knee joint.

METHODS: Participants’ (male [n=7] and female [n=14], 21.3 ± 2.1 yrs, 1.69 ± 0.09 m, 69.3 ± 13.0 kg) right hip, knee, and ankle kinematics were captured with a 3D motion capture system. Electromyography (EMG) signals were recorded from rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM), semimembranosus (SM), and biceps femoris (BF) muscles. EMG were normalized to maximum voluntary efforts. Participants performed 10 single leg landings from a 30 cm height onto a force platform before and after static knee loading. Participants were seated and secured to a chair while the right knee was flexed and secured at 35° during static loading. A load (150 N/females, 200 N/males) was applied at a 90° angle to the proximal leg for 10 min. Maximum, minimum, range of motion (ROM), and angular velocities were assessed for the hip, knee, and ankle joints, while normalized average EMG (NAEMG) and average vertical ground reaction forces (aVGRF) were calculated over the initial 200 ms of landing. Rate of force development (RFD) was calculated during the landings. One-way ANOVAs analyzed kinematics variables, NAEMG during loading, aVGRF and RFD; while a two-factor ANOVA (condition x muscle) analyzed NAEMG. Alpha level was set at 0.05.

RESULTS: Maximum hip flexion velocity decreased (87.1 ± 56.9 vs. 56.9 ±63.4 °/s, p < 0.01). Minimum knee flexion velocity increased (-14.9 ± 25.2 vs. -27.9 ± 34.2 °/s, p < 0.02). Minimum knee ad/abduction velocity decreased (-528.5 ± 127.5 °/s vs. -399.9 ± 129.3 °/s, p < 0.001). Ankle ROM decreased (56.2 ± 8.5°vs. 52.6 ± 8.5°, p < 0.001). aVGRF decreased (1297.1 ± 392.4 N vs. 1231.3 ± 392.4 N, p < 0.02). RFD had a non-significant trend (16,602 ± 1057 N/s vs. 17,368 ± 1447.6 N/s, p = 0.076). NAEMG was significant between muscle groups (RF: 46.4 ± 28.9% vs. VL: 26.2 ± 27.7 %, p < 0.01; VM: 56.3 ± 46.6% vs. VL: 26.2 ± 27.7 %, BF: 38.8 ± 27.8%, and SM: 32.4 ± 23.0%, p < 0.02).

CONCLUSIONS: Changes in velocity parameters are attributed to the altered mechanical behavior of the knee joint tissues and may contribute to changes landing mechanics. Overall, results indicate modified hip and knee control in response to potential reduction in knee joint stiffness.

Copyright © 2019 by the American College of Sports Medicine