Summer is fast approaching and the mountains are calling. As sports like mountain running, climbing and the novel Scandinavian swim-run competitions become popular, the question of how to transition from urban life to nonstop action can be tricky. We spoke with professional guide Graham Austick, certified by the International Federation of Mountain Guide Associations (UIAGM), about how to prepare.

The gym has less to do with it than you might think, according to Austick, who says that for endurance-style adventures which require many hours a day of climbing, cycling or running, starting to eat right well in advance is essential.

Begin by steering clear of processed foods that may contain added sugar and to reduce or eliminate refined sugar, even if your trip is weeks away.

Eating right between adventures

"Endurance sports require slow release energy," says Austick, "Refined sugar does exactly the opposite: It gives you extreme peaks and thrusts of energy, and that can make you irritable."

It requires training the body to eat foods that provide slow-release energy, he says, because sugar cravings occur when the body exhausts its food supply during a long run or while ascending a mountain.

Examples include nuts, steel-cut oats, quinoa and non-starchy vegetables such as spinach, kale, tomatoes, broccoli, onions and asparagus.

Get your sugar fix from fruit instead of candy because most fruit has a low glycemic index, meaning that it releases energy slower than that of products containing refined sugar.

Instead of buying packaged smoothies for training runs, Austick says all it takes is adding salt to fruit juice to keep you hydrated and magnesium to prevent muscle cramps when you're taking your body's limits up a notch.

Adding desk-work to your cardio program, yes, really

Going running while you're not at the office is great for your cardiovascular fitness, but what about all those hours when you're required to sit?

Toning your muscles is a question of tensing them up for two to three seconds and relaxing them in sets of ten to 20, says Austick, who advises doing this...at your desk, no special chairs or exercise balls are necessary.

"Gyms work," he says, "But you really don't need weights or equipment, toning your muscles is a simple question of stimulating them."

A half hour in the morning and a half hour in the afternoon of repetitions -- while focusing on your posture -- could be enough to balance out your cardio regime and significantly improve your fitness.

Sitting is what you make of it

"So if you're a desk jockey and have a few moments to sit," says Austick, "Start focusing on different muscle groups, especially the core, which is everybody's weakest point."

For isometric, or static core training at work, sit up straight without leaning against the back of your chair for extended periods.

To perform isotonic core contractions, lock your toes around the legs of your chair and pull your hips down, tightening the abs and back muscles.

It's important to cover all muscle groups, says Austick, but your core is your center of balance and is important for activities such as climbing.

Austick, who reminds readers that during endurance activities, proper hydration and intake of easily digestible carbohydrates is essential, is also co-owner of the Lyngen Lodge, located in the fjords of northern Norway near Tromso, where activities include hiking, kayaking, riding and glacier exploration.