Periods 'can be the difference between first and last'

Middle-distance runner Jessica Judd broke down in tears when her period cycle ruined any chance of 800m glory at the World Championships in Moscow in 2013, and she failed to qualify from her heat.

Here she explains just what effects the menstrual cycle can have on female athletes, and what lengths she went to prevent the heartbreak in Moscow happening again, with the help of guidance from marathon world record holder Paula Radcliffe.

Speaking to Sonja McLaughlan, Judd says the week between her period and the start of the cycle can cost her up to 15 seconds over 3km - "the difference between first and last" in a race.

This clip was broadcast on 5 live Sport on Wednesday 21 January 2015.