The phrase 'luxury wellness retreat' has been applied to hotel spas with eucalyptus steam rooms, to resort packages that include a massage and a green juice at breakfast, to long weekends in converted farmhouses where 'wellness' means a yoga class and a good night's sleep. None of these are bad things. But they're not what this piece is about.

For most of the year, fitness happens in stolen time. Early mornings before the commute. Lunch breaks squeezed between meetings. Forty-five minutes if you're lucky. A fitness retreat is the opposite — it's what happens when you give training your full attention, in a place designed for it, for a week. Here's what makes Portugal one of the best destinations in Europe to do exactly that.

Juice detox retreats are having a moment. More people than ever are heading to Portugal to press the reset button — to stop eating for a few days, get out of their routine, and see what happens when you give your digestive system a rest. But if you've never done one before, the prospect can feel a little daunting. This guide covers everything a first-timer needs to know.