Gaited Horses can be "sored" to create lift, animation, and to change the timing of the front feet.
Soring can be accomplished by:
 long toes  big feet (add more weight)  heavier shoes  adding boots  adding toe weights  quarter boots tightened on the coronary band  heavy contact which interferes with the horse's normal leg flight  sitting on the cantle of the saddle  placing the saddle past the last rib  saddle digging into the loins  the feet pounding on the ground (concussive practices)
None of these practices should be used with Icelandic Horses, but some are.
In North America, we tend to like to have our Icelandic Horses barefoot, it at all possible. Barefoot allows the horse's hoof to spread and contract as necessary. It may not be possible to have barefoot horses in Iceland, but it is possible in North America. It all depends on your terrain and how much you ride. If the horse has genetically good feet, it may not be a problem to be barefoot, and may actually be healthier for him!
The natural barefoot trims work really well for Icelandic Horses.
Let's see if we can move away from seeing pictures like this of Icelandic Horses. Well, not only no pictures, but no pulling on the horse's mouth, no strapping the mouth shut, and no bits that cause this type of reaction.
The definition of collection is a combination of three factors:
 Engagement of the hindquarters, which means that the pelvis tips down (tail down) and in (rotating the bottom of the pelvis in and under the horse), bringing both legs under the mass of the horse.
 Bascule (rounding) of the back. Engagement of the hindquarters must happen for the back to round up.
 Lifting of the base of the neck. This allows the neck to telescope and the head to freely offer it's relaxed position slightly in front of the vehicle.
In tolt, the pelvis is doing the opposite of the engaged position; it is tipping up (tail up) and out (rotating the bottom of the pelvis up and out away from the mass of the horse).
This action, starts the back to hollow. The back cannot "round" when the hindquarters have not been engaged.
In collection, the lowering of the pelvis (engagement of the hindquarters) is a *sustained* lowering.
Sustained lowering never happens in tolt.
Going to the front of the horse: lifting the head and neck lowers the base of the neck, which makes tolt an earth-bound gait. The vector of the movement is down; earth-bound, which is the opposite of collection.