Ice skating spins come in three basic flavors: upright spins, sit spins, and camel spins. At the senior level, these spins are nearly always executed on one foot, the only exception being the cross foot spin (an upright spin executed on the toes of both feet). In each spin position, spins can be executed in the forward or reverse direction. A right handed skater executes a forward spin by rotating counter-clockwise on the left foot, and executes a back spin by rotating counter-clockwise on the right foot. Left handed skaters rotate clockwise in spins, with forward spins executed on the right foot and back spins on the left.
In their simplest form, spins consist of pushing or stepping into the spin, rotating some number of times in position, and exiting the spin on one foot. Instead of simply pushing or stepping into the spin, the skater can jump into position in several ways. Spins with this type of entry are referred to as "flying" spins (or less often, "jump" spins).
In a properly executed spin the skater rotates over a fixed position on the ice. Such a spin is said to be "centered". Spins that do not rotate over a fixed position, but drift off from the starting spot are said to "travel". In general, traveling in a spin is an error, except when it is purposely made a part of the spin's entry. The most common example of this is the traveling camel spin that begins with the skater rotating in a camel position that travels across the ice, but ends as a centered camel spin.
Over the years as skaters began to fill their programs to the brim with triple jumps, the importance of spins in free skating programs went into a period of decline. To some extent, the judges also contributed to this decline by not rewarding well executed spins to the extent they could have. In recent years, however, the rules have been adjusted to increase the importance of spins in competitive skating. In the short program, the required deductions were altered so that errors in jumps and spins received equivalent deductions; and in the free skating program rules requiring a "well-balanced" program were added. Free skating programs that do not meet the requirements for being well-balanced, by having too many or too few elements of various types, are subject to required deductions. Finally, the word went out to the judges that well executed spins should be properly rewarded. While skaters who are superior jumpers still beat skaters who are superior spinners, there has been enough of a shift that champion skaters must have quality spins in their programs to win.
The speed with which a skater rotates depends upon the initial angular momentum (turning motion) entering the spin and the distribution of mass (body parts) in the position of the spin. Once having pushed into the spin, a skater cannot increase the amount of angular momentum. At best it will remain nearly constant, decreasing in the course of the spin due to friction acting on the blade on the ice. While angular momentum remains nearly constant, skaters can, nevertheless, change the angular speed of rotation (the number of turns per second) by changing positions. By bring mass in closer to the rotation axis (pulling in arms and legs) a skater can increase the angular speed of the spin. The speed of rotation will decrease when mass is moved away from the rotation axis.
When skaters enter a spin (either by stepping, pushing or jumping in) they are setting up the spin on the spinning edge with the initial angular momentum of the spin. Immediately upon entering the spin, skaters pull in their arms and legs to increase the speed of rotation. While the spin is rotating the skater is generally turning on a small circle which defines the center of the spin. At the end of the spin arms and legs are extended away from the rotation axis to slow down the rotation speed. Forward spins end by stepping to the opposite foot and exiting on a back outside edge, back spins by exiting on the back outside edge of the spinning foot. In either case, the exiting back edge need not be held for very long. In some cases skaters will hold the edge only briefly, quickly placing the toes of the free foot on the ice to come to a stop.
Spins executed in one position are called solo spins. Spins in which there are changes of position and/or foot are known as spin combinations (or combination spins). When a change of position occurs with no change of foot the angular momentum may either decrease or stay the same, but it cannot be made to increase. The angular speed of the spin, however, may increase if the change in position brings more of the skater's mass closer to the rotation axis, and will decrease if the opposite is true. When there is a change of foot in a spin, skaters can get a little extra push in the change. This will increase the angular momentum of the spin and can make up for lost momentum in the first half of the spin if the skater pushed in too slowly, or lost momentum by grinding an edge or toe picks into the ice.
At the novice level and above, combinations spins of at least one change of foot and one change of position are required. The most commonly used example of this is the spin combination: forward camel - forward sit - back sit. It is not unusual to find the vast majority of novice skaters use this combination in the short program. There are two reasons for this. First, the change of position from forward camel to forward sit is one of the easier to execute; and second, that change of position results in a change of mass distribution that causes the speed of rotation to increase. A slightly more difficult combination is: forward camel - back camel - back sit. The change in position from back camel to back sit is slightly more difficult but also results in a change of mass distribution that increases the speed of rotation. The most difficult example is: forward sit - back sit - back camel. The back sit to back camel transition is the most difficult of these three examples. It also results in a change of mass distribution that causes a significant decrease in the speed of rotation. To keep this spin going requires a lot of speed in the back sit and good technique transitioning into the back camel. You will only rarely see this spin combination used in a program.
A fast, well centered spin requires significant upper body strength and fine control of body position.
Take a rag doll and spin it. The arms and legs will go flying outwards away from the rotation axis. The arms and legs of a skater want to do the same thing in a spin. To pull in and keep pulled in skaters must use the strength of their arms, shoulders, and thighs to control position. In a fast spin the strength requires is as great as for a triple jump, and it must be sustained over a longer time interval since a triple jump lasts at best about a second, while a spin is generally sustained for several seconds.
Correct body position is essential for a spin to be correctly centered. For a spin to be centered a skater's mass must be distributed relatively symmetrically about the rotation axis, and their center of mass must be located over the center of the spin. If this is not the case the skater becomes a gyroscope.
Take a gyroscope which is not spinning and try to balance it on its end, or in a tilted position. You can't. Set it spinning, however, and it will balance in an upright or even tilted position. While a gyroscope spinning on a table in a tilted position will stay up, it will not stand still. It instead wobbles in a big circle around the end touching the table. This is a basic characteristic of rotating things and it applies to rotating skaters.
If a skater starts spinning in a tilted position so that their center of mass is not directly over the center of the spin, their shoulders will starts to wobble just like the gyroscope. If the tilt is minor the result is a traveling spin as the skater adjusts their position and edge to fight the wobble. If the skater is tilted too much the wobble can be large enough to pull the skater out of position and wreck the spin. In a combination spin it may pull the skater far enough out of position that the change of foot or position cannot be made successfully.
Because of the gyroscopic action, skaters must also be careful how they change position. It is impossible to move one body part (e.g., an arm or leg) without other parts moving also (perhaps a little, perhaps a lot). To keep a spin centered, changes of position must be done in a way that keeps the skater's center of mass over the center of the spin. If not, the gyroscopic wobble will be introduced and the spin gets into trouble.
The greater the angular momentum of the spin the greater these gyroscopic-like effects, and the greater perfection of balance and position required. A fast, well centered spin that is sustained for many seconds requires remarkable skill and should not be dismissed lightly.