[Stephen Seiler PhD has been on the faculty of the Institute of Health and Sport, Agder University College, Kristiansand, Norway, since 1997 and is currently an associate professor. He is also an adjunct research consultant at a large regional hospital. He focuses a lot of his efforts on teaching and research the the physiology of endurance training and performance. His web site, Master Athlete Physiology & Performance (http://home.hia.no/~stephens/index.html) is dedicated to examining and explaining the physiology and training methods of the endurance athlete. The text below is reprinted from the web site with the author's permission.]
Propelling the body on skies requires intense work by both the arms and the legs. When we ski hard we are "asking" the heart to deliver high blood flow in several different directions at once. Once an exercise employs a large quantity of muscle (running, rowing, cycling in experienced riders), then the oxygen consumption limitation falls back to the heart and it's ability to deliver oxygen. So, what happens in skiing when we add maximal arm exercise to maximal leg exercise? The answer is: little or nothing. Studies in the laboratory have demonstrated that adding arm exercise to maximal leg exercise during a VO2 max test increases oxygen consumption by only a tiny percentage, or not at all. The cardiovascular system works under a constant limitation related to maintaining sufficient blood pressure in the system.
It is a lot like what happens in an old house when you're taking a shower and somebody turns on the faucet in the kitchen, while someone else flushes the toilet. Pretty soon, the shower becomes a drizzle. To maintain water pressure in the pipes, you can't have too many valves open at once. The same is true in our cardiovascular "pipes". When arm exercise is added to leg exercise, blood flow to the legs actually decreases due to constriction of the leg arteries. This extra blood flow is than available for the arms. The body maintains blood pressure, by controlling how how much each artery is "opened."
During skiing the contribution of the upper body to movement velocity varies from perhaps 10% during the classic diagonal stride to 100% during double poling. During skating uphill (the double dance), the upper body contributes 50% or more of the total force. The endurance capacity of the upper body has always been important to the skier. Today, with the addition of arm-intensive skating techniques, this is even more true. Consequently, there has been a lot of recent research investigating the endurance capacity of the upper body of elite skiers, and its relationship to performance.
Special ergometers have been developed for measuring oxygen consumption during either double poling, or during the alternating arm movements used during the diagonal stride. We developed a poling ergoemter for our lab using a Concept II rowing ergometer with a custom ski pole type handle. The devices range from turning a rowing machine on end to highly advanced ergometers that measure force output and movement velocities at each ski pole, while simulating the free-floating movement of the legs.
One meaningful comparison to make is the "peak oxygen consumption" achieved during double poling relative to VO2 max measured during uphill treadmill running or roller-skiing. In untrained populations, upper body VO2 peak will only be about 60% of whole body max. In recreational and well trained skiers, the ratio increases to 70 to 85%. Remarkably, in the elite skiers tested in Norway and Sweden (and no doubt other word class skiers from around the globe), this ratio averages 90% and sometimes approaches 95%!
I think this is a valuable point for all of us who wish to improve our skiing. One of the areas where most endurance athletes are weak is upper body endurance and power. Among elite skiers, an interesting pattern occurs during the season. Whole body maximal oxygen consumption peaks very early in the seasonal build-up. However, performance peak during the season seems to correspond to the peaking of upper-body endurance capacity, measured as upper body peak VO2.
Now we come to a common question: If I weight train, will this improve my endurance capacity? Unpublished observations by Swedish investigators (Ekblom and Berg) indicate that the maximal leg strength is only slightly greater than what is seen in the average person. However, when an endurance test is used in the same movement, such as 50 consecutive leg extensions, the skiers are clearly superior, even compared to most other endurance athletes (rowers may be the exception). What this means is that there is no relationship between maximal leg strength and leg endurance. In practice, elite skiers do little or no general weight training for the lower body. For the older (50+) skier, I would still recommend a lower body weight training program only for the purpose of maintaining muscle mass.
The upper body is a different story. Performance time for a 60 meter sprint double-poling test is strongly related to peak torque produced by the triceps group during strength testing. Faster times are produced by those with greater arm strength. Furthermore, there is preliminary evidence here in Norway that even> a short term, intense upper body strength training program results in increased upper body VO2 max and endurance time in standard load testing on a special ski ergometer.
What is going on here?
I have told you repeatedly that whole body maximal oxygen consumption is limited by the heart (along with the endurance capacity of the muscles), not how much muscle or strength you have. So how can strength training improve upper body endurance and peak oxygen consumption? Here is the difference. The total muscle mass of the upper body is not great enough to maximally stress the heart during high intensity work. For example, peak heart rate achieved during a double poling test may be 10-20 beats lower than observed during maximal treadmill running.
What this means is that in the unique condition of upper-body only endurance exercise, the heart is no longer the limiting factor, the muscle is. Consquently, dedicated specific training designed to increase skiing specific strength AND endurance can result in more total muscle available during double poling, or other arm-intensive skiing techniques. In the summer training of the elite, it is common to see arm-intensive work like kayaking added to the program in order to help close the endurance gap between the upper and lower body.
This is a useful lesson many masters skiers can take away from observing the "big-boys."