Skiing - Downhill

Skiing is a recreational activity and competitive sport in which the participant attaches long runners or skis to boots or shoes on the feet and uses them to travel on top of snow. Aside from recreation and competition, skiing has been used for military purposes and even travelling in areas that experience heavy snowfall. Many types of competitive skiing events are recognized by the International Olympic Committee, and the International Ski Federation.

History
The oldest and most accurately documented evidence of skiing origins is found in modern day Norway and Sweden. The earliest primitive carvings circa 5000 B.C. depict a skier with one pole, located in Rødøy in the Nordland region of Norway. The first primitive ski was found in a peat bog in Hoting, Sweden which dates back to 2500 or 4500 B.C. Joel Berglund reported in 2004 the discovery of a primitive ski, or "85cm long piece of wood", carbon tested by researchers in 1997 while excavating a Norse settlement near Nanortalik, Greenland. The primitive ski dated back to 1010, and is thought to be Greenland's oldest ski brought by Norsemen circa 980 A.D.

The word "ski" itself is one of a handful of words Norway has exported to the international community. It comes from the Old Norse word "skíð" which means split piece of wood or firewood.

Alpine ski racing as an organised sport commenced in both America and Australia. The first recreational ski club was formed in 1861 at Kiandra, Australia, where the first documented international downhill carnival was also held.

Downhill Skiing
Also called Alpine skiing, typically, takes place at a ski resort or dry slope. It originated in the European Alps, and is characterized by fixed-heel bindings that attach at both the toe and the heel of the skier's boot. Sub-genres of alpine skiing include:

Freestyle
Heliskiing
Competitive classes include: slalom, giant slalom, Super-G, Downhill, and disabled skiing.

In alpine skiing, for every 1000 people skiing in a day, on average between two and four will require medical attention. Knee injuries account for 33 percent of injuries. Most accidents are the result of user error leading to an isolated fall.

Ski Trail Ratings
In most ski resorts, the runs are graded according to comparative difficulty so that skiers can select appropriate routes. The grading schemes around the world are related, although with significant regional variations.

Typically, grading is done by the resort, and grades are relative to other trails within that resort. As such, they are not classified to an independent standard; although they are likely to be roughly similar, skiers should be cautious about assuming that grades in two different resorts are absolutely equivalent.
North America, New Zealand and Australia
In North America, a color–shape rating system is used to indicate the comparative difficulty of trails (otherwise known as slopes or pistes). Australian ski slopes also share the same rating system.

Ski resorts assign ratings to their own trails, marking a given trail according to its relative difficulty when compared with other trails at that resort. Although slope gradient is the primary consideration in assigning a trail rating, other factors come into play — including trail width, normal snow conditions and whether or not the resort regularly grooms the trail.

**Ski trail difficulty ratings in North America**
Trail Rating	Level of difficulty	Description
Green circle	Easiest	The easiest slopes at a mountain. Green Circle trails are generally wide and groomed, typically with slope gradients ranging from 6% to 25% (a 100% slope is a 45 degree angle).
Blue square	Intermediate	Intermediate difficulty slopes with grades commonly ranging from 25% to 40%. These slopes are usually groomed. Blue Square runs make up the bulk of pistes at most ski areas, and are usually among the most heavily trafficked.
Black diamond	Advanced	Amongst the most difficult at a given mountain. Black Diamond trails tend to be steep (typically 40% and up) and may or may not be groomed, though the introduction of snowcats has made the grooming of steep slopes both possible and more frequent.
Double black diamond	Expert Only	These trails are even more difficult than Black Diamond, due to exceptionally steep slopes and other hazards such as narrow trails, exposure to wind, and the presence of obstacles such as steep drop-offs or trees. They are intended only for the most experienced skiers. This trail rating is fairly new; by the 1980s, technological improvements in trail construction and maintenance, coupled with intense marketing competition, led to the creation of a Double Black Diamond rating.
Variations	Various	Variations such as doubling a symbol to indicate increased difficulty, or combining two different symbols to indicate intermediate difficulty are occasionally used, as is often in Colorado at Winter Park resort and other Colorado ski resorts. One example is a diamond overlapping a square to indicate a trail rating between a Blue Square and a Black Diamond. Many resorts throughout Colorado use a double diamond with an "EX" in the center to mark a run with extreme terrain, even more difficult than a double diamond. Other resorts, such as Smugglers' Notch, Vermont, Le Massif, Quebec, and Mt. Bohemia, Michigan, use triple black diamonds. The combination of symbols is comparatively rare at U.S. ski areas; most ski resorts stick to the standard 4-symbol progression (with the exception of the common EX runs in Colorado). Non-standard symbols for standard ratings may be encountered at some ski areas. Bogus Basin, a resort near Boise, Idaho, uses orange diamonds on trailheads for trails that are indicated in the resort's Alpine Guide as double black diamonds. Jiminy Peak, MA uses two variations of normal trail ratings; one is a blue square with a green circle inside of it used to represent an easy-intermediate trail. The other is a blue square with a single black diamond in it, used to represent an intermediate-hard trail.
Terrain parks	Various	Terrain parks are whole or portions of trails that can offer a variety of jumps, half-pipes, and other special "extreme" sporting obstacles beyond traditional moguls. The trails are typically represented by an orange rectangle with rounded corners. Usually, the terrain park will carry its own trail rating, indicating the level of challenge. A terrain park with a Black Diamond or Double Black Diamond rating would contain greater and more challenging obstacles than a park with a Blue Square rating.