BACKGROUND: As supporting musculature fatigues, generalized knee laxity increases, specifically dynamic knee valgus (DKV), which results in risk of musculoskeletal injury. While there is moderate research on how fatigue affects DKV in athletic populations, there is a gap in the literature relating to the general, untrained population. The purpose of this study was to determine the effect fatigue has on the DKV angle in untrained populations. METHODS: A sample of 31 subjects (age 22.29+2.47 years; 58% female) performed a drop vertical jump (DJV) test from a 30 cm plyometric box in front of the VST ProTM system by VirtuSense Technologies, measuring the DKV angles (in degrees). The DVJ test was performed before and after completion of a fatigue protocol which included wall sits, squats, and vertical jumps. Participants were considered fatigued once reached a 15% decrease of their pre-fatigue max vertical jump height, as measured with the Vertec Vertical Jump device standard protocol. Pre- and post-fatigue measurements were analyzed with paired t-tests.​ RESULTS: Results indicated a statistically significant difference in DKV angles for both the right lower extremity (RLE) (-1.18+2.26, p=0.007) and left lower extremity (LLE) (-1.19+2.2; p=0.005). In males, there was a statistically significant difference in comparing the LLE (-1.40+1.08; p<0.001) pre- and post-fatigue knee valgus angles, however there was no statistically significant difference in the RLE (-.7879+1.59; p=0.103). In females, results indicated no statistically significant difference in pre- and post-fatigue DKV angle for the LLE (-1.03+2.76; p=1.32) but did find statistical significance in the RLE (-1.46+2.65; p=0.031). CONCLUSIONS: The results of our study suggest quadriceps fatigue may not play as large of a role in the increase of DKV angles as the fatigue protocol within the procedures primarily biased quadriceps muscles. Although there was a statistically significant change in DKV angles in the RLE and LLE of all participants, it did not surpass the minimal detectable change for DKV measured by the VST ProTM, but it was above the level of the standard error measurement of 1 degree. Additional research should investigate the comparison of a quadriceps versus hip musculature fatigue protocol. GRANT OR FUNDING INFORMATION: Funding received from Western Kentucky University, College of Health and Human Services Quick Turn-Around Grant (QTAG)

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