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EFFECTS OF AUDITORY AND VISUAL STIMULI ON REACTION AND RESPONSE TIME DURING COUNTERMOVEMENT JUMPS

Abstract

Russell Lowell, David Saucier, Harish Chander, Reuben Burch, Zachary Gillen. Mississippi State University, Starkville, MS.

BACKGROUND: The countermovement jump (CMJ) is commonly used to assess athletic performance and/or athlete readiness. Since many sports require athletes to react and respond to external visual and auditory stimuli, it stands to reason that examining reaction and response time during a CMJ may provide a unique indicator of the underlying neural mechanisms preceding muscular contraction during athletic endeavors. The purpose of this study was to examine the effects of an auditory (AUD) vs. visual (VIS) stimulus on reaction time (REACT) of the tibialis anterior (TA), medial gastrocnemius (GM), vastus lateralis (VL), and biceps femoris (BF), and response time (RT) during the CMJ. METHODS: Ten college-aged males and females participated (age=23+4yrs., height=176+11cm, body mass=72+13kgs). Bipolar surface electromyographic (EMG) signals were collected from the TA, GM, VL, and BF. Subjects completed six CMJs on force plates, three with an AUD stimulus and three with a VIS stimulus, in random order. The AUD stimulus was a beep noise, the VIS stimulus was a light appearing on a screen in front of the subjects. Subjects performed a maximal CMJ immediately upon hearing or seeing the stimulus. REACT for each muscle was taken as the time between the receiving the stimulus and the point at which the EMG signal for the muscle rose 3 standard deviations above the EMG signal during the 1-second preceding the stimulus. RT was taken as the time between receiving the stimulus and the point at which the force signal decreased 5 standard deviations below the force signal during the 1-second preceding the stimulus. Two-way repeated measures ANOVAs examined differences between stimuli and among muscles for REACT, while a dependent samples t-test to examined differences between stimuli for RT. RESULTS: For REACT, there was a main effect for muscle such that VL,BF < TA,GM (p≤0.007), with no other differences (p≥0.104). RT was significantly different such that AUD

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