TODAY | April 22, 2014
>>> back now at 8:52. the new workout obsession across the pond that could catch on here in the states. nbc's katy tur checked it out.
>> reporter: no one ever said it would be easy. and if they did, it was probably too good to be true.
>> up to ten pounds in 48 hours .
>> reporter: but just because it has to be hard, it doesn't mean it can't be fun. ditch the treadmill, say goodbye to the rowing machine , and drop your spotter. staying in shape has never been more entertaining. at least for londoners. so what about riding a bike in the same place for 45 minutes without going anywhere? they say that is fun as well, when you do it like this. let's see.
>> here we go.
>> reporter: long the mecca of serious cycling, the uk now has cycle, with a p. take out the drudgery and add lights. music. and a screaming -- make that motivating instructor.
>> you get lost in almost like a club scene and then you kind of finish. your lights come up and you realize that you're just drenched in sweat.
>> it's like having fun , but you end up working out, by accident.
>> reporter: don't like the dark? how about a pop-up gym. a view of st. paul's.
>> we pop up and do classes, just like awesome things like this. outdoors, rooftops, iconic locations in london.
>> reporter: too calming? try an exercise raid. get high on endorphins and health smoothies, all before 8:00 a.m .
>> i think clubbing at the start of the day is --
>> the way forward.
>> there's no hangover either.
>> reporter: dancing away the pounds. saluting the sun. and mastering that climb.
>> come on!
>> reporter: it may still be work, but it hurts so good. for "today," katy tur, nbc news, london. send me back to new york for a snowstorm.
>> sweating sounds so much better when you're british.
>> looked like fun. that's cool.
>>> coming up, the dynamic duo