He had a special singlet designed and undoubtedly carbon shoes. Makes you wonder how much raw human potential has progressed vs just having better equipment and track surfaces?
If it's just the singlet and the shoes you would expect lots of other runners to get close too. It's surprising that the previous record stood for 27 years if the equipment has been progressing since then.
Not when you consider that El Garrouj was a freak. The reason it stood for so long is that it was a helluva record.