Skate skiing is also sometimes called freestyle skiing (Fig. 27.2). The skate technique is very similar to ice skating in that the power-generating phase occurs off a foot and limb that is externally rotated in relation to the plane of progression. The popularity of skate skiing is largely due to the fact that it is metabolically more efficient and skiers can attain greater speeds [6]. Skate skiing must be done on a wide, packed, groomed skate deck. Poling is done with both poles simultaneously in synchronization with propulsion from each leg as opposed to the contralateral arm/ski motion in the classic discipline. Unlike classic skiing where the skiers’ center of mass (CoM) changes minimally from medial to lateral, skate skiers shift their CoM significantly as they alternate propulsion from limb to limb.

There are variations of the pole and ski timing that skate skiers will use depending on the terrain. For example, some techniques are best for conserving energy and skiing flat terrain. Other techniques expend more energy but are better for sprinting and climbing. A skate skier provides ski propulsion by first gliding on the flat ski and then pushing posterior lateral while transferring weight to the medial foot and edging the medial ski edge into the snow in the terminal propulsive phase. The skate skier pushes off the ski as it is gliding anterior and lateral. The poles provide more propulsion in skate skiing than in classic which is why the poles are longer [13].

Some ski racing formats combine the two disciplines of Nordic skiing in pursuit racing. In this format, racers ski a set distance in one discipline and then the second half of the race is skied in the other discipline after changing skis and poles (and boots for those who choose not to use “combi” or “pursuit” boots). The skier who was first in the first discipline starts first and the other skiers are sent out after him or her based on the amount of time they were behind after the first discipline. The field then pursues and attempts to overtake the leader. This racing format requires that skiers be proficient at both the classic and skate disciplines.

Overall, XC skiing has a relatively low incidence of both overuse and acute injuries. Estimates of overall injury rates vary from 0.1 to 0.5 injuries per 1000 skier days [6, 14, 15]. The lower extremity is the most common site of both acute and overuse injuries. Interestingly, one study found that XC skiers were injured more often while doing non-ski training activities [16]. Overuse injury risk factors are similar to other sports: training errors, poor technique, and improper equipment.

Acute injuries are typically caused by falls or collisions with stationary objects and are much more common on downhills than flat or uphill sections due to increased velocity [14]. Boyle and colleagues described the most common mechanism of acute injury to the lower extremity as “an external rotation abduction moment applied to an entrapped ski.” This mechanism of injury is much more common in Alpine skiing as the free heel of XC skiing bindings allows more freedom of movement of the lower extremity during a fall.

Chronic exertional compartment syndrome has a high incidence especially affecting the anterior compartment in elite skate skiers [17, 18]. High tibialis anterior muscle (TA) activation during both swing and stance phases of the ski cycle may be a mechanism of anterior compartment syndrome. It was initially speculated that the mass of the ski and boot required increased activation of the TA muscle during the swing phase and this was the most likely mechanism of injury but Federolf and Bakker’s EMG study in elite skiers with anterior compartment syndrome showed that differences in TA muscle recruitment patterns were more significant during the glide phase than during the swing phase indicating that the TA was also important in balance [19]. These high-activation patterns during both the glide and swing phases of ski gait likely contribute to the high incidence of anterior exertional compartment syndrome.

Low back pain is not uncommon in both classic and skate skiing due to repetition of hip and back extension. Iliotibial band syndrome , hamstring injuries, and chondromalacia patella are more common in skate than classic as reported by Schelkun [20].

In an injury survey study done at the American Birkebeiner ski race (the largest ski marathon in North America) in 1996, foot and ankle injuries were the most common injury followed by hand/wrist injuries [15]. First metatarsal phalangeal (mtpj) joint pain has been described as more common in classic skiing than skate [20]. Classic technique requires more dorsiflexion of the first MTP joint than skate skiing due to the demand for dorsiflexion required during the terminal kick phase of the ski cycle. Individuals with first MTP joint dysfunction such as bunion deformities and or hallux rigidus or other arthritic conditions of the great toe joint may be predisposed to pain in this joint in the classic XC discipline. Skating technique, which utilizes more lateral forces from the ski and more power from the poles for propulsion, does not require as much dorsiflexion of the first MTP joint.

Vogel described XC ski footwear as a combination of an Alpine ski boot and a running shoe [21]. Ski boots will have different structural features depending on whether they are intended for classic or skate disciplines. There are also hybrid boots or “combi” boots which combine structural features that are suitable for both classic and skate disciplines. Combi boots are also sometimes referred to as “pursuit” boots because pursuit racers must ski both classic and skate disciplines. Hybrid boots offer cost savings and convenience over having to buy two different boots. Other variations in boot structure are influenced by the ability of the skier and snow surface. In general, recreational skiers tend to place a higher priority on warmth and comfort while racers may be willing to sacrifice some warmth and comfort for performance features in a ski boot.

Boots for XC skiing provide the means for transferring power from the foot to the ski through a secure binding system. So before we discuss the boots in detail we must first discuss bindings.

Bindings have evolved from leather straps and cable devices to three-pin and to today’s most commonly used bar system. While leather and cable systems have become mostly obsolete, three-pin binding systems are still utilized for Nordic backcountry skiing but both modern classic and skate use bar systems. In the bar system, a steel bar is embedded in the distal end of the boot sole and is secured into a clip on the binding. This allows for a stable attachment of the boot but also freedom of motion much like a door hinge [22]. The free heel of Nordic ski bindings allows for more power during the propulsive phase in both classic and skate disciplines as the foot can plantarflex in order to maximize power transfer to the ski. The free heel also reduces (but does not eliminate) the risk of lower extremity fracture and catastrophic knee injuries. XC bindings do not release in a fall as they do in Alpine skiing. Ski-binding manufacturers may at some point introduce bindings that release in a fall but currently there are no such bindings on the market.

Unlike Alpine ski equipment manufacturers, who have standardized their systems so that all boots and bindings are compatible, there are two distinct bar-binding systems for XC skiing (Fig. 27.3). New Nordic Norm (or NNN) and Salomon Nordic System (or SNS) are very similar in appearance with a grooved plastic binding plate attached to a metal clip [23]. The grooved plate articulates with matched grooves on the bottom of the boot and allows for better control of the ski especially at high speeds and downhills when the boot is flat on the ski. The metal clip secures the bar at the toe of the ski boot. The main difference between NNN and SNS is the geometry of the longitudinal groove(s) on the binding plate and boot bottom. NNN uses two thin parallel grooves and SNS uses one wider groove. The newest version of NNN is NIS (Nordic Integrated System) where the ski manufacturers make the ski with an attached binding plate. This system is compatible with NNN boots and allows for the proper binding placement in the ski shop by clicking the binding in place without having to drill holes. SNS also has a newer binding system that utilizes two forefoot bars for attachment which is claimed to provide better control of the ski. One bar is at the distal aspect of the boot and second is just distal to the metatarsal-phalangeal joints. There are other variations of these two binding systems and technological and design advancements will likely contribute to further changes in the future.

In determining which binding system to utilize, most ski retailers advocate first fitting the boots and, once the most comfortable and suitable pair has been selected, then matching the binding system to the boot. The rationale for this approach is that boot comfort is so important and the differences between NNN and SNS binding systems are negligible for most skiers [24].