Sydney, April 20 (IANS) Pulling over for a 15-minute nap during a long drive reduces your sleepiness level, but a 15-minute break that includes a brisk walk makes no difference.

 
 Chris Watling, sleep technician and masters student at Queensland University of Technology's (QUT), said the study also found that when subjects said they felt alert after a rest break, their response times did not demonstrate it.
 
 Watling gave a group of participants -- aged 20 to 25 years -- a simulated driving task to test their ability to detect and respond to potential hazards such as merging vehicles or vehicles that brake suddenly.
 
 During the hazard-perception driving task, participants had to click a button when they recognised a potential hazard while watching a video of driving on real roads. The simulated 'trip' included city and country driving, according to a QUT release.
 
 "Hazard perception is a very important driving skill and it has been shown to be the only driving skill that has a consistent relationship with crashes," he said.
 
 "Our participants were slightly sleep-deprived before undertaking the driving task. Instead of the recommended eight hours' sleep, the participants had six to seven hours' sleep.
 
 "We attached electrodes to the participants to record their brain activity levels so that we could get an objective measure of sleepiness. Participants undertook a simulated-driving task for two hours; each participant then had either a 15-minute nap or a 15-minute rest break that included 10 minutes of brisk walking, followed by another hour of simulated driving.
 
 "We tested each participant in the nap mode and the rest break mode on separate occasions," concluded Watling.
 
 Watling found that the nap group's brain activity levels showed a decrease in sleepiness after the nap, which was to be expected, but the rest break group showed no decrease in sleepiness although they reported feeling more alert after the rest break.
 
 He also stressed that longer nap durations could lead to suffering from what is called sleep inertia, which is a short period of time of excessive sleepiness.