The UK’s toughest workouts

Flatline, Gymbox

Described by Gymbox as the ‘hardest and most dangerous gym class in the world’, it’s no surprise that you have to sign a death waiver to take part in Flatline. But don’t let that scare you off – there are paramedics and cardiologists on site at all times. Flatline aims to test all elements of strength and stamina. Participants wear a 12kg weighted vest as they work their way through tasks such as weighted rope climbs, atlas stone throws and box jump burpees, made increasingly difficult over a 45-minute period. With a compulsory oxygen station installed as part of the cool down, this is certainly for the more sadistic of you.