BACKGROUND: During many sports activities, landing is a reoccurring action that receives little attention from athletes and coaches. There is an increased risk of musculoskeletal injury with repetitive loading and high impact forces during landing. To mitigate this effect, it is important to understand the role fatigue plays on landing kinetics during landing. PURPOSE: This study aimed to address two objectives: (1) how fatigue affects GRFs during landing, (2) to investigate how lower body fatigue influences the amount of muscle activity during landing. METHODS: Sixteen healthy adults (6M,10F, HT: 1.69±0.08m, WT: 76.94±18.47kg, 24.12±6.06yrs) participated in this study. Participants were equipped with Electromyography (EMG) sensors placed on their Rectus Femoris (RF) and Gastrocnemius (GA) to record electrical activity of the muscles. Participants performed five single-leg drop-landings in a rested state from a 30.48cm platform onto a force plate to measure normal and parallel forces upon landing. Following the initial landing task, participants engaged in a progressive exercise protocol utilizing the Monark Cycle Ergometer. Cycle protocol increased 50W every minute, until participants could not maintain 50rpm for three consecutive seconds. Throughout this exercise period, heart rate (HR) was continuously monitored using a Polar telemetric monitor, HR and Rating of Perceived Exertion (RPE) were recorded in minute intervals. Upon completion participants were asked questions about their perceived fatigue levels. Subsequently, participants immediately repeated the series of five drops, whilst EMG and GRF data were recorded. Each variable was analyzed for differences using a paired t-test (α=0.05). RESULTS: Peak Mediolateral GRF increased during landing from 34.01±81.52N to 70.91±81.31N (p=0.01) after fatiguing exercise. Peak vertical GRF were not different before and after fatigue (p>0.05). Average EMG for both RF and GA were not different before and after fatigue (p>0.05). CONCLUSION: Peak valgus stress during landing increases after a bout of fatiguing exercise. Although mediolateral stress may increase following fatigue, muscle activity of the rectus femoris and gastrocnemius do not. These data suggest that athletes and coaches should take steps to actively mitigate injury risk during activity where high levels of fatigue may occur.

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