Researchers are now reporting you can gain alot by listening to music in your Ipod / MP3 player while running.
From the BBC website
Dr Costas Karageorghis and Professor Peter Terry, sports psychologists from Brunel University West London and the University of Southern Queensland, Toowoomba respectively found music increased energy efficiency by 1-3%, meaning athletes could run further on the same amount of oxygen.
The researchers further found women seemed to benefit more than men.
Maybe this new find explains why elite runners are banned from listening to Ipods while running.
Read more at BBC Health