Taking on a North Pole unsupported expedition is physically the hardest adventure in the world. You will carry your full camp with you at all times. The strains of the challenge crave a daily intake of 5000 calories or more, making your load so much heavier. You must climb ice ridges, jump leads and push your sled over countless obstacles.
Skiing unsupported to the South Pole is easier but difficult enough. The surface is flat and there is no open water, however, there are very high head winds, violent storms and huge crevasses at some places. In addition you'll fight an uphill battle and altitude.
Expect your back and joints to take most of the beating. Pulling tires is the traditional workout prior to Arctic travel. Practice for what you'll perform. Pulling tires is absolutely essential to strengthen your hips and back for the monotonous pull of a heavy sled. If you don't, you'll have very slim chances of making it, at least unsupported.
Vigorous strength training and aerobic sessions are also highly recommended. Work hard until around three weeks before departure. Maintain a light workout level until on the ice. Expect bad falls. The sled will pull you in bad positions, crash into you and even roll on top of you. You'll need strong bones and tight muscles to take the beating. Aim to work out 2 hours per day for at least 6 months prior to the expedition.
Despite the high calorie consumption you will lose weight rapidly on the expedition. Here is the good news about preparation; feel free to stuff yourself. You should put on at least 15 lbs. Go easy on the French fries though, you will need your arteries in top shape. Go into Sumo-wrestling mode; fatten up on the healthy stuff like fat fish and vegetable oils. Aim to get strong and big, not fat and weak.
It is a must to practice polar trekking and camping prior to the expedition. Preparation treks commonly take place in Greenland, Northern US or Norway. Count around 7-10 days for the trip. Use one of the organizers listed on this website. Paul is one of the world's best guides on supported polar treks; Borge Ousland is great for unsupported treks. Sjur Mordre is a unique veteran of both. He knows the gear down to the smallest detail like nobody else. Most unsupported expeditions turn to Sjur for advice and specialized gear. The greatest polar farer of our time is Rune Gjeldnes, who along with friend Torry Larsen made an unsupported crossing of the Arctic ocean in 2000. Rune, however, doesn't organize trips. There are in addition several British and Russian polar veterans around. No matter who you choose for a patron, most polar veterans are extremely skilled, friendly and helpful.