The Arctic Action Sets
1986 NL Technic catalog
8 new sets were released in 1986, the most in a single year since the line began. In addition to a go-cart and tractor model, 2 new Universal Sets as well as the Arctic Action sets were released. These were the first sets to appear in the US under the name of Technic, replacing the Expert Builder name. New elements included the worm gear, the action figure and several action figure accessories, such as skis, helmets and chairs.
The Arctic Action sets: The 4 Arctic Action Sets comprise the first Technic theme, based around a polar expedition. The series included a small ski car, a helicopter, a 6-wheeled truck and a pneumatic helicopter base and were given 8600 series set numbers. From the 1986 Lego press release: "Imagine a Mountain Rescue Base with a pneumatic powered helicopter platform. Or Snow Ranger vehicles with snow ploughs, and the new action figures which can even wear skis. They all add up to a really exciting new build-and-play idea."

The Arctic Action theme
The Arctic Action theme was the first attempt to add play value to the sets beyond just their construction and technical functions. It was the only Technic theme until the Competition/Cyberslam theme of the late 1990's.
The Action Figure: Lego had been producing figures in some form since the early 1970's, but the action figure was the first to be fully articulated. The head, shoulders, elbows, hips, knees and feet were all movable to some degree. The patent for a new ball and socket joint, originally filed in 1985, shows a hip joint that consists of a pin with a ball at the end. The ball fit into a hollow socket on the thigh, allowing rotation. But the thigh also squeezed against the pin with enough force that the joint could remain in any position by friction, allowing the figure to be posable. This joint formed the basis not just of the Technic figures, but also of several other Lego dolls.
DK patent 157,062
8620 Snow Scooter:
The smallest of the Arctic Action sets and the smallest Technic set to date, the 8620 was scaled for the new action figure. The model had only one real function-the rack and pinion steering. The steering used not only the typical toothed plates and steering arms but featured an angled steering wheel held in place by cross axles and toggle joints. This small buggy would form the prototype for an increasing number of smaller vehicles over the next several years.

1986 sets:

8035 Universal Set
8055 Motorized Universal Set
8620 Snow Scooter
8640 Polar Copter
8660 Arctic Rescue Unit
8680 Mountain Rescue Base
8842 Go Cart
8849 Tractor
By Isodomus