How will controversial shoe tech affect Olympic marathon trials?

Welsh marathon runner Dewi Griffiths says advancements in running shoe technology are like being given "free time" in races.

The 29-year-old is hoping to qualify for Tokyo when he competes in the Olympic marathon trials in London on Friday.

The technology, which was pioneered by Nike, helped Eliud Kipchoge run a marathon in under two hours in 2019 - though a team of pacemakers meant it was not a recognised record.

World Athletics then clarified the technology that can be used in shoes, and several world records have since been broken in endurance races.

Critics argue the new technology gives runners an unfair advantage, while others have praised the developments.