Acute Effects of Specific Actions after the "On Your Marks" Command.

Improved temporal sequencing of high - intensity muscle contractions prior to the sprint start may maximize motoneuron excitability and may enhance fast twitch fiber recruitment and sprint start effectiveness. The aim of the study was to assess a) the electromyographic activity of the gastrocnemius lateralis, biceps femoris and vastus femoris muscles under exposure to specific voluntary, dynamic actions (quick skipping or tuck jumps that sometimes sprinters perform after the "on your marks" command) and to an external involuntary stimulus (WBV-whole body vibration) and b) the effectiveness of the above stimuli applied on the activation level of lower limb muscles in order to produce neuromuscular activation the very last moment just behind the blocks, as this is measured by the RT and time in 1.5m and 3m after the sprint start. Ten male sprinters executed sprint starts under 4 experimental conditions after the "on your marks command": 1^st condition - without performing any action, 2ndperforming tuck jumps, 3^rd performing quick skipping and 4^th after being exposed to vibration stimuli. No significant difference in average muscle activity was observed after evaluation of the EMG raw data for the tuck jumps and quick skipping actions. No significant differences were, also, observed for RT and time in 1.5m and 3m in conditions 2 to 4. [ABSTRACT FROM AUTHOR]