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DOES LOWER BODY FATIGUE INFLUENCE BIOMECHANICAL FACTORS DURING LANDING?

Abstract

Andrew Craig-Jones, Haley Gilbert, Priya Giddens, Daniel Greene, Jonathan Ruiz-Ramie. Augusta University, Augusta, GA.

BACKGROUND: Landing is an important part of many physical activities in today’s modern culture. Repetitive loading and high impact forces during landing often place an athlete at risk for musculoskeletal injury. Understanding the effect of fatigue on landing kinetics is an important step in potentially reducing future risk of injury. The purpose of this study was to compare muscle activation and ground reaction forces during landing before and after fatigue. METHODS: Five participants completed a series of single leg drop landings before and after a fatiguing protocol. After collecting biometric data from participants, each participant was equipped with an electromyographic (EMG) sensor on the rectus femoris (RF) and tibialis anterior (TA) of their dominant leg. The participants then performed 5 drop landings from a height of 30.48cm to act as the control condition. All participants were given time before these trials to familiarize themselves with dropping technique. Following the control condition, the participants were seated on a cycle ergometer and instructed to cycle until voluntary exhaustion. The cycle ergometer began with 0W resistance and increased 50W every minute until the participant ended the exercise. Participants were then immediately placed back onto the dropping platform and instructed to complete another 5 single leg drop landings. During all trials, the participants dropped onto their dominant leg and were barefoot. During each landing, EMG and ground reaction forces (GRF) were collected for analysis. Vertical and mediolateral GRF was processed to select peak force and loading rate for each trial. The resulting variables were averaged across condition and the average was used for analysis. Each variable was analyzed for differences using a paired t-test (α=0.05). RESULTS: Peak vertical GRF during landing was 2182.20±457.2N which was significantly greater (p=0.005) than peak GRF after fatigue (1673.75±415.19). Average mediolateral GRF were not different before and after fatigue (p>0.05). Average EMG for both RF and TA were not different before and after fatigue (p>0.05). Average RF EMG increased from 30.85±14.4 µV to 45.06±25.5µV and TA EMG stayed relatively stable at 397.57±313.9µV before exercise and 388.59±316.46µV after exercise. CONCLUSION: We conclude that vertical GRF is reduced after a fatiguing exercise, but horizontal GRF, RF EMG, and TA EMG remain unchanged.

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