It has a motion sensor and locks the hard disk in place when it is moving to prevent damage to the hard disk and just plays from the cache. This does mean that if you are jogging for more than 20 minutes it will stop playing until you stop moving.<br><br>Without sensibility no object would be given to us, without understanding no object would be thought. Thoughts without content are empty, intuitions without concepts are blind.<br>-- Immanuel Kant, "Critique of Pure Reason
"For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled." - Richard Feynman