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CO-CONTRACTION DURING A REACTIONARY DROP JUMP: SINGLE-SPORT AND MULTI-SPORT ATHLETES ARE NOT DIFFERENT

Abstract

BACKGROUND: Multi-sport athletes are exposed to many different positions and situations, thus requiring a higher level of neuromuscular function to complete rapid, whole-body movements in different sports. The use of a reactionary drop jump task to analyze neuromuscular function between single-sport and multi-sport athletes has yet to be examined. Therefore, the purpose of this study is to determine the influence of single-sport and multi-sport participation on rectus femoris and biceps femoris co-contraction during the landing and propulsive phases of a reactionary drop jump. METHODS: Sixteen former high school athletes (age: 22.06 ± 2.80 years; height: 1.70 ± 0.09 meters; weight: 162.00 ± 26.16 pounds) were recruited with an athletic background of participating in 1 high school sport (8 total, 4 males, 4 females) or more than 1 high school sport (8 total, 4 males, 4 females). Participants performed 3 MVICs for the left and right Rectus Femoris and Biceps Femoris for normalization (12 total MVICs). Next, 5 reactionary drop jumps and 5 reactionary drop lands were completed in a randomized order based on a custom light system that indicated which task to perform. Electromyography (EMG) data were collected using four Noraxon Surface EMG Dual Electrode Transmitters, sampling at 1000 Hz. EMG data were imported to C-Motion Visual3D for processing during the landing and propulsive phases of the drop jumps, and imported to MATLAB for calculation of normalized EMG during the trials and co-contraction index (CCI). Due to no differences in CCI between sexes, data were separated into two groups for analysis (Single-Sport and Multi-Sport). However, CCI differences were observed between limbs. Therefore, analysis included 2 x 2 repeated measures (Phase of Movement x Right and Left CCI) MANOVAs with 1 between groups factor (Sports Group). RESULTS: No significant differences in CCI were observed between single-sport and multi-sport athletes during the landing (F2,13 = 0.064, p=0.938; Wilks’ λ = 0.990) and propulsive (F2,13 = 0.004, p=0.996, Wilks’ λ = 0.999) phases of the drop jump. CONCLUSION: Multi-sport athletes do not prioritize stability by co-contracting the musculature about the knee joint differently than single-sport athletes during a reactionary drop jump. However, the asymmetry in CCI was an unexpected outcome. Therefore, future research should investigate differences in the amount of asymmetry between athlete types.

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