Sports Medicine: Just the Facts

COMPETITION

Elite Level Competition

• The International Ski Federation (FIS) governs inter-
  national competition. The FIS establishes race rules,
  schedules, doping control systems, athlete injury sur-
  veillance, and most other aspects of World Cup and
  World Championship racing.


• The specific events held at elite competitions are varied
  in both distance and technique. Formats include sprint
  (1 km), sprint relay, middle distance (5 km, 10 km,
  15 km), team relay (4 × 5 km, 4 × 10 km), long distance
  (30 km, 50 km), classic/skate pursuit, and others.


• One unique aspect of elite cross-country skiing is that
  the athletes frequently compete as both sprinters (1 km)
  as well as marathon skiers (30 or 50 km) within the
  same race schedule. Most competitors will train and
  race in both the classical and skating techniques.

Nonelite Competition

• Marathon distance races are held in nearly all of the
  countries of Northern, Central, and Eastern Europe as
  well as Japan, North America, and Australia.


• In the United States a full calendar of local, regional,
  and national marathon races are scheduled throughout
  the winter months. The largest of these, the American
  Birkebeiner is 52 km long with over 7000 participants.


• High school and college cross-country ski teams are
  common in the Northeast, upper Midwest, and Western
  states. These competitions include races 5 to 15 km in
  length with both classic stride and skating formats.

BIOMECHANICS

TECHNIQUE

Diagonal (Classic) Technique

• The diagonal stride technique has been used for cen-
  turies and remains a popular style for ski touring and
  back country skiing.


• In the diagonal stride forward propulsion is accom-
  plished through alternating kick and glide actions of
  the skis. This requires a full stop of the kick ski to
  propel the skier forward. Backward slip of the planted
  ski is limited by the application of high friction kick
  wax on the cambered portion of the ski surface. The
  requirement to plant the ski to generate thrust limits
  the maximum speeds obtainable (Renstrom and
  Johnson, 1989).


• In the diagonal stride the poles are used primarily for
  balance but can contribute up to 30% of forward thrust
  in higher-level skiers (Renstrom and Johnson, 1989).
  Double poling (planting both poles simultaneously) is
  utilized as increasing tempo limits the effectiveness of
  the kick and glide action.

Skating Technique

•Developed in the late 1970s this new technique has

rapidly evolved and become the method of choice for

most recreational skiers. Skating is the only technique

used in both Biathlon and Nordic combined competi-

tions.

• The skating technique generates forward momentum
  by driving the skis at an angle to the direction of travel
  in a motion analogous to speed skating. There is no
  kick phase and thus no stopping of the ski during the
  cycle. Several different strides (V1 skate, V2 skate,
  Marathon skate) are utilized depending on terrain and
  skier tempo.


• Double poling is used in most skating strides to trans-
  fer upper body energy to the skiing surface and can
  provide up to 60% of the forward propulsive force
  (Smith, 1992).

Biomechanical Comparison of the Techniques

• Skating is much more energy efficient than the diago-
  nal stride technique (Hoffman and Clifford, 1990). In
  addition, with skating there is no need for a high fric-
  tion kick wax; so low friction glide waxes can be used
  along the entire surface of the ski.


• These factors combined with the use of extremely
  light weight composite construction materials as well
  as improvements in skiing surface preparation have
  resulted in a 10–30% increase in average speed since
  the 1950s (Hoffman and Clifford, 1990; Street,
  1992).

INJURY EPIDEMIOLOGY AND

PATHOPHYSIOLOGY

OVERALLINCIDENCE

•Historically, the injury rates in cross country skiing are

reported between 0.1 and 5.63 injuries per 1000 skiers

(Sherry and Asquith, 1987; Boyle, Johnson, and Pope,

1981). The true incidence is difficult to determine as

skiing is not generally limited to a confined venue.

• In the limited data available from more controlled cir-
  cumstances, such as endurance races, the incidence
  was found to be substantially higher at 10 to 35 per
  1000 skiers (Renstrom and Johnson, 1989; Butcher
  and Brannen, 1998). The majority of these injuries
  were fatigue related.

CHANGINGINJURYPATTERNS

• As the technique and equipment have changed, several
  equipment-injury relationships have been suggested
  (Schelkun, 1992; Lawson, Reid, and Wiley, 1992;
  Lindsay et al, 1993; Bovard, 1994; Dorsen, 1986).
  
  
  1. Increased pole length with the skating technique
     accentuates demands on the shoulder and elbow.
  
  
  
  

476 SECTION 6 • SPORTS-SPECIFIC CONSIDERATIONS