Find out how our athletes fared against the Kalapalo warriors in the festival of death.
The athletes travel to South Africa for some serious stick fighting.
Keep on running - but which of our athletes made it to the finish?
Which of our athletes faired best at the north-east Indian sport.
Our athletes find the local customs a little hard to swallow.
It's cricket... but not as we know it.
Our athletes join the Senegalese Wolof tribe.
In their final challenge, who will be the ultimate Last Man Standing?
In southern Ethiopia they take on the deadly sport of Suri stick-fighting, but before they can enter the ring they must learn to live with a tribe whose way of life has barely changed for hundreds of years. This means a spot of tribal scarring and some internal cleansing known as the Dokai.
They head to a harvest festival in Burkina Faso, a tiny land-locked country in West Africa. There they must ask for help from sacred crocodiles and ancestral masks before taking part in a brutal inter-village wrestling contest involving some of the country's top fighters.
In the Himalayas, the lads are living with Nepalese Sherpas and learning to train at extreme altitude in freezing conditions. Their goal is a punishing race up a mountain in the shadow of Everest, carrying a slab of sacred rock on their backs for the construction of a Buddhist prayer wall.
The lads are in central Brazil at the height of the rainy season to race canoes against the Wauja tribe. However, they have more than just a fast-flowing river to contend with, as they face the ever-present piranhas, a bloody initiation ceremony and the wrath of some very angry village women.
The athletes are in Bhutan to learn the national sport of archery. They have to fire arrows more than twice the Olympic distance, over the heads spectators, to hit a target the size of a dinner plate. It is so difficult that even the experts have a special dance when anyone scores a hit, and the lads are right at the centre of a serious grudge match between two villages.
The athletes head for Kamchatka in north-east Asia to live with Koriyak nomads in temperatures that can drop to minus 40 degrees Celsius. After acclimatising, training to run in snow and helping with the spring reindeer corralling, they travel to the Koriyak spring festival to race the locals in their annual endurance race.
The athletes take on the sport of sikaran, a brutal form of kick-fighting where the hands and arms may only be used for defence. After being put through their paces in a tough training regime, they must prove themselves worthy of wearing the prized red pants of a sikaranista before fighting in an open contest.
The athletes are in Indonesia, facing the prospect of driving pairs of racing buffalo on a waterlogged drag track while hanging on to a special racing plough. To have any chance of success they need to get their animals to trust them, but bonding sessions with semi-tamed buffalo are not easy.
The athletes take on the ancient Indian art of Kushti wrestling - sweaty, hand to hand combat in a concrete sand pit. If they survive intensive training in a Kushti guru's school, they will be rewarded with a chance to take on the local professionals in front of 15,000 fight fans, who have a reputation for cutting up rough if they don't like what they see.
In their final challenge, the athletes take part in an ocean-going race between islands off Papua New Guinea. It is two days of paddling outrigger canoes over shark-infested waters against some of the world's greatest canoe experts - the Titans, a tribe of sea nomads who have lived on these waters for centuries.