Vertical Jump Landing Fatigue: the Kinetic, Kinematic, and Muscular Adaptations

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von Hacht, Markus
Biomechanics , Jumping , Jump Landing , Fatigue , Landing
Understanding how fatigue affects task performance is crucial for understanding injury risk. Historically, the tests used to measure fatigue and the effects of that fatigue were not always similar to the tasks that generated that fatigue. Many studies that examine fatigue in jumping implement a pre-fatigue test, followed by a fatiguing protocol, and then a post-fatigue test. If the pre-fatigue and post-fatigue tests are not functionally similar to the fatiguing task, then the information obtained may not accurately represent the true effect of fatigue on the specific task. To avoid misinterpretation the testing tasks must be similar, or ideally identical, to the repetitive, fatiguing task. Therefore, in this study, a vertical countermovement jumping task was recorded continuously and the landing biomechanics were analyzed over time to explore how fatigue was manifest as jump performance decreased. The purpose of this study was to identify how landing biomechanics changed as the degree of fatigue increased. Kinematic, kinetic and muscular data were collected from 10 experienced jumpers, and 14 novice jumpers. For each participant, data were collected continuously during the continuous execution of 60 maximal vertical jumps, where the rest time between jumps was four seconds. Independent samples t-test assessed the difference between the novice and elite group. For the last 45 jumps of the fatigue protocol, slopes with 95% confidence intervals and correlations were computed to assess the rate of change for each variable and the relationship between the fatigue measures, and the landing biomechanical variables. Results demonstrate there was no significant difference between the novice and elite group mean slope for all variables. Three of the landing biomechanical variables had slopes significantly different from zero: the maximum knee angle (Kmax), the location of the maximum ground reaction force (GRF Loc), and one of the stiffness measure (Stiff5). Additionally, the changes in jump height are not correlated with changes in landing biomechanical variables (correlations < 0.50), which presents an important consideration for using jump height as a single variable for determining if individuals are at risk for a fatigue-related injury.
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