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Access Type

WSU Access

Date of Award

January 2016

Degree Type


Degree Name



Health Education

First Advisor

Qin Lai


Fractionating reaction time (FRT) chronometrically separates central (PMT) from peripheral (MT) processing, allowing for analysis of the variables that may have a timing effect on either. The purpose of this study was to determine the effect of foreperiod regularity and muscle size on the components of FRT. Forty-four male (n = 21) and female (n = 23) healthy Wayne State University students responded to a visual stimulus in a simple reaction time task, either by alternating foreperiod by block (Exp1) or by alternating muscle size by block (Exp2). All participants completed six blocks of eight trials using their right-side, with five seconds separating trials and sixty seconds separating blocks. FRT and surface electromyography (sEMG) data were collected digitally through the E-Prime 2.0 software and a BIOPAC MP100 System, which were fully integrated and time synced. Employing a counter-balance of condition, participants responded with a rapid thumb press for all trials with the foreperiod alternating by block (Exp1) or alternating between thumb press and elbow extension by block with all trails maintaining a regular foreperiod. Bipolar sEMG signals were recorded from the small abductor pollicis brevis (both experiments) and the large lateral triceps brachii (Exp2). In Exp1, significantly shorter times were observed during the regular foreperiod for mRT and mPMT. A significant interaction existed between foreperiod grouping and sequence of foreperiod administration for mRT and mPMT. Specifically, beginning testing with a regular foreperiod produced the shortest mRT and mPMT, and beginning testing with an irregular foreperiod produced the longest mRT and mPMT. A sex difference between foreperiod groups was not significant mRT, however, females demonstrated a significantly shorter mPMT in both foreperiod groups. MT was not significantly different for all analysis. In Exp2, significantly shorter times were observed with the small muscle for mRT, mPMT, and mMT. Also, the relative-timing analysis demonstrated a discrepancy between muscle sizes, supporting effector-dependence. No significant interaction existed between muscle size grouping and sequence of muscle size utilization. A sex difference was observed for both muscle size groups, with males demonstrating a significantly shorter mRT and mPMT, with no significant difference in mMT. Collectively, these findings highlight the effects of foreperiod regularity, influence of condition order, muscle size, and sex differences in simple reaction time. Future recommendations are made with potential implications for athletic training, coaching, and rehabilitation.

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