How science is fine-tuning our elite footballers

In February, football's lawmakers approved the analysis of a player's performance during live matches, via a tracking device in the shirt. So what impact will this have on a player's health, game management - and the half-time team talk?

The Fifa Women's World Cup final this summer was remarkable, and not just because England came within one game of playing in it. One in 12 Americans watched at least part of the game live, making it the most watched football game in US history, while Team USA secured a record third title, thanks in no small part to their midfielder Carli Lloyd scoring a 13-minute hat-trick. The third of these saw her lob the Japanese goalkeeper from the halfway line.

Less obvious, but possibly of more significance, were the small black gadgets about the size of an old Nokia mobile phone that the winning players were wearing between their shoulder blades. The final was the first major international match since the laws of the game were changed in February to allow players to wear performance-tracking devices during a match.