The two-hour marathon.
For distance runners, it's a mystical goal equivalent to the four-minute mile that Roger Bannister broke in 1954; a test so difficult some have estimated it may be 50 years or more before anyone achieves it.
Now the $270 billion market for athletic shoes and apparel is fueling an assault on the mark.
Nike and Adidas have announced separate plans to attack the barrier, with both introducing shoe lines linked to the effort. Wireless tech giant Vodafone last month said it was backing a third bid, hoping data gleaned from the quest will translate into wearable technology.
The leader so far is Nike, which came within a whisper of the barrier...