Haim have injections ''in the ass'' every day on tour.

The Californian trio - sisters Este, Alana and Danielle Haim - admit they struggle to perform well if they have been partying, so think the key to a successful tour is to stay healthy and watch what they eat.

Alana Haim explained: ''I'd love to think we were the Rolling Stones back in the day, getting drunk and partying all the time, but we're not. We're too scared to get sick.

''So do your B12 shots. We've been on tour for two years and finally cracked the health code; take vitamins, eat greens, drink juices. If you're not healthy, you can't play a good show.

''B12 shots go in the ass, yes. Does it hurt? I have a cushion, it's not really a problem for me.''

The 'Falling' hitmakers also find the time to work out on the road as it is easy to put on weight during a tour.

Alana said: ''Every band gains 10 pounds on tour. After the show, everything is closed, you're fuelled by McDonalds so in hotels we run. Work out, keep fit. Shorts are my stage uniform and my favourite shorts are becoming too small. Este always says you gotta keep that ass tight.''

While the sisters enjoy being on the road together, they always take time to stay in touch with their parents as they ''miss'' them.

Alana told Q magazine: ''We owe our parents everything, they introduced us to music, gave us our first instruments and wanted us to become a band.

''So I always call my parents to let us know I'm still alive and OK on the road. I miss them lots, I do - it's so dorky to say it but I really do. There's times when you just miss your mom.''