"Go" signal intensity influences the sprint start.

INTRODUCTION Loud sounds can decrease reaction time (RT) and increase force generated during voluntary contractions. Accordingly, we hypothesized that the loud starter's pistol at the Olympic Games allows runners closer to the starter to react sooner and stronger than runners farther away. METHODS RT for the 100/110 m athletics events at the 2004 Olympics were obtained from International Association of Athletics Federations archives and binned by lane. Additionally, 12 untrained participants and four trained sprinters performed sprint starts from starting blocks modified to measure horizontal force. The "go" signal, a recorded gunshot, was randomly presented at 80-100-120 dB. RESULTS Runners closest to the starter at the Olympics had significantly lower RT than those further away. Mean RT for lane 1 (160 ms) was significantly lower than for lanes 2-8 (175 +/- 5 ms), and RT for lane 2 was significantly lower than that for lane 7. Experimentally, increasing "go" signal intensity from 80-100-120 dB significantly decreased RT from 138 +/- 30 to 128 +/- 25 to 120 +/- 20 ms, respectively. Peak force was not influenced by sound intensity. However, time to peak force was significantly lower for the 120 dB compared to the 80-dB "go" signal for untrained but not trained participants. When a startle response was evoked, RT was 18 ms lower than for starts with no startle. Startle did not alter peak force or time to peak force. CONCLUSION Graded decreases in RT may reflect a summation-mediated reduction in audiomotor transmission time, whereas step-like decreases associated with startle may reflect a bypassing of specific cortical circuits. We suggest that procedures presently used to start the Olympic sprint events afford runners closer to the starter the advantage of hearing the "go" signal louder; consequently, they react sooner but not more strongly than their competitors.