Since the advent of the skating technique in cross-country ski racing, emphasis on upper body fitness has gradually become a critical component of cross-country ski training. A major focus of this training has been on the development of short-term double poling power output. This focus has primarily come about because of recent research. Several researchers have shown that effective upper body power output during ski skating relates strongly to race velocity and competitive results. Olympic and World Championship medal winning Russian Biathletes tested at the Lake Placid Olympic Training Center demonstrated modest VO2max values (a measure of aerobic capacity, that were not different than U.S. National Team members), but 30% higher short-tern double pole power outputs than U.S. Biathletes. Additionally, ski times at U.S. Biathlon National Championships have been highly related to upper body power (R=0.95, an ³R² of 1.0 is a perfect relationship), but not VO2max. Recent work by Steve Gaskill, Bob Serfass, and Ken Rundell extended this concept by including a large population of skiers with varied abilities. This study demonstrated a strong relationship (r=0.90) between upper body power and race velocity in 158 Minnesota high school skiers. The results of these studies support a structured upper body training regimen to improve upper body power in developmental and elite skiers.
Biomechanical studies of uphill ski-skating have determined that 60 to 70 percent of the effective uphill force impulse is derived from poling, more than twice that determined for the classical skiing technique. Other studies have suggested that the function of the legs during V-1 skating appears to be primarily as support for the body and to induce lateral motion, while the function of the upper body is propulsive in the forward direction. Force data collected during uphill V-1 skating at 3 different velocities showed that poling forces increased with increasing velocity, while skating forces remained unchanged. This data strongly suggests that poling during uphill V-1 skating is the major contributor to forward velocity. Currently, there is a paucity of data on ski skating on flat terrain; however, the available data suggests that the upper body contribution to forward propulsion is about 30%. This, in part, is due to the smaller ski angle (to the direction of travel) required on the flats.
Although cross-country skiing is an endurance activity which requires a high aerobic capacity (VO2max), estimations of required energy output during uphill skiing (made during World Cup competition; by the Finnish biomechanist Pavo Komi) far exceed the highest VO2max values on record (for humans). The actual estimates approached 150 ml/kg/min and 80 ml/kg/min of oxygen consumption, for uphill and flat skiing, respectively (Bjorn Daahlie has a reported VO2max of 95 ml/kg/min). This means that the power output to climb at race pace must come from both aerobic and short-term anaerobic energy systems. Given that the upper body is a major contributor during climbing and that climbing compromises about 50% of total race time, it should come as no surprise that a short-term maximal double poling power test is a good predictor of ski performance.
The test used at the Lake Placid OTC to assess short-term anaerobic power utilizes a specially designed double poling machine which can accurately measure power (defined as the amount of work performed in a period of time, the unit of measure being watts [W]). The test lasts approximately 4 minutes and consists of double poling at a constant rate while the resistance increases incrementally every 20 seconds. When the athlete can no longer maintain a pre-determined pace, the test is terminated. Information from the test includes a time to failure and peak 10 second power output (W and W/kg body wt.). Six years of data collected using this test has indicated that values for successful competitors approach 5 W/kg body wt. for men and 4 W/kg body wt. for women. Successful junior men and junior women produce 3 and 4 W/kg/body wt., respectively. For athletes who do not "score" well on the double pole power test, recommendations for specific power workouts are made. We have found that athletes who follow the training recommendations can make big improvements on the power test, and their "per kilometer" ski time improves accordingly.
Since the natural (or active) recruitment of cross-country skiers in this country comes primarily from the pool of aerobic athletes (runners), knowledge of appropriate training to improve upper body power is imperative (since most runners lack upper body power, as demonstrated in a study by Gaskill, Serfass, and Rundell). Additionally, appropriate incorporation of the upper body is critical to proper ski technique, which could be compromised when the athlete has insufficient upper body power (or strength). Little research is available on strength/power development for cross-country skiers, but common sense tells us that a strength program is necessary during some point in a skiers career. According to research, juniors and women could gain much improvement in skiing speed by increasing upper body power. Given the paucity of research on strength training for this aerobic sport, caution should be used when prescribing a program. General guidelines for coaches to follow should include: 1) Ski-specific exercises; double poling, roller board, dips, chins, abdominal work, hill bounding, etc. 2) General strength exercises should be closely monitored so the athlete does not make gains in muscle mass that are not ski-specific (this is especially important for exercises using weights, and for males vs. females). Remember, skiing is primarily an aerobic sport, and extra weight not used in skiing is an added energy cost when climbing. 3) Power is not just a function of strength, but also of time. Therefore, speed should be incorporated in the exercises (explosive type movements) for optimum power development.