The fittest of them all: endurance athletes

Photo courtesy of Marit Bjørgen and four other top finishers from the Skiathlon gasping for air after all-out effort.

Photo courtesy of
Marit Bjørgen and four other top finishers from the Skiathlon gasping for air after all-out effort.

Swimmers, marathon runners, and cyclists get the most credit for being fit, but cross-country skiers outdo them all

Tom Rodgers
Arlington, Texas

Mirror, mirror on the wall, who’s the fittest of them all? You may never have this conversation with the quicksilver on your wall, but many athletes are waking up today in Sochi, Russia and asking themselves that question. Just what do we mean by fitness? Do we mean the strength found in weightlifting competitions? Do we mean the explosiveness found in American Football players or 100-meter sprinters? Or the balance and control of figure skaters and gymnasts?

In the current Sochi games, we have the most popular sports like downhill skiing, a mix of strength and speed; figure skating, mostly skill and presentation; speed-skating, which is similar to both distance running and cycling; and snowboarding, a test of balance not unlike surfing. If we define “fitness” in a medical way, we mean cardiorespiratory fitness, or the ability to process oxygen and turn fat into energy. Most doctors agree this kind of fitness makes you live longer and helps your brain resist aging.

Physiologists have a convenient single number that measures this fitness: VO2-max, which is the maximum rate of oxygen consumption as measured during incremental exercise, sometimes referred as “aerobic capacity.” It’s measured in milliliters of oxygen consumed per minute per kilogram of body weight (ml/kg/min). Size does matter when it comes to aerobic capacity, which is why most endurance athletes have lower body mass than larger athletes from sports emphasizing short-term bursts of strength and speed.

How do VO2-max numbers stack up across various sports? Male Olympic swimmers usually come in somewhere with a VO2-max around 70, top marathon runners something like 75, and pro cyclists as high as 88. In most of these sports, women tend to come in about 10 points lower than comparable men. Even though men weigh more than women, they have a higher percentage of muscle, and as you might have guessed, testosterone helps men burn oxygen rapidly.

But by far the highest VO2-max numbers come from cross-country skiers, who have tested as high as 96 ml/kg/min. What makes them the fittest athletes? The crosscountry events are some of the longest in the Olympics, up to 50 kilometers (31 miles), and they cover the toughest terrain, including steep climbs. Compared to other sports like swimming (mostly upper-body muscles), cycling (lower body without much upper body) and running (mostly lower body with arms swinging freely), cross-country skiers actively use their upper-body muscles to pole up hills and in the flats, and of course need strong hips and legs to move the skis. Because they use both the upper- and lowerbody in tandem, they must also engage core muscles in the abdomen and lower back, some of the largest in the human body.

I first became acquainted with top crosscountry skiers and biathletes via triathlon, where many European triathletes come from a cross-country skiing or biathlon background. I met Uros Velepec when he won the 2000 Ultraman Triathlon World Championship in Hawaii (about 2.7 times longer than the famous Hawaii Ironman triathlon) where I got fifth place overall. He then went on to become the coach of the Slovenian men’s national biathlon team. Many other long-course triathletes in North America train the aerobic engine in the winter on cross-country skis.

In the 2014 Sochi games, this conflagration of oxygen burned brightest for the Norwegian cross-country team on the opening weekend. The fire started with the women’s Skiathlon, a mixture of classic-style skiing for 7.5 kilometers on narrow trails with longer poles (resembles exaggerated walking or an indoor elliptical trainer); followed by a quick change of skis and 7.5 more kilometers using the newer freestyle method (looks more like skating on the snow).

On a multiloop course with wickedly tough climbs, a group of three Norwegians and one Swede broke away from the pack and fought ski-to-ski to the last 400 meters. Then Marit Bjørgen followed the breaking Swede Charlotte Kalla up the final climb, drafted in behind, then passed inside on the final turn to pull away for a clear win.

That left two other Norwegian women, Heidi Weng and Teherese Johaug, to fight for the bronze medal. Johaug had done most of the work breaking the wind while leading the original four-woman breakaway, so faded to the surging Weng who took the bronze.

If you need still more evidence that cross-country skiers process the most oxygen and put out the most energy at the finish, all four women collapsed flat into the snow and continued to pant rapidly for several minutes after the event. We’ve all seen this kind of thing in the old days when marathon runners and Ironman triathletes would collapse at or before the finish line, but modern training techniques and race nutrition have all but eliminated the dramatic collapse in these other sports. Not so in cross-country skiing, where the herculean effort requires the very last decimal of their remaining aerobic capacity.

Adding to the emotional fatigue, both Bjørgen and Weng said they were skiing hard for teammate Astrid Uhrenholdt Jacobsen, who heard on Friday that her brother and training partner had died. Bittersweet tears were apparent in the Norwegian dressing tent after the Skiathlon medals. The cause of death was not given. Jacobsen decided to go ahead with Tuesday’s cross-country sprint despite being in mourning.

You could see oxygen depletion again the following day in the men’s freestyle sprint, where the top finishers all collapsed at the line. Even in the more controlled exertion of the men’s biathlon, where competitors must freestyle-ski around a challenging hilly loop, then stop to fire a .22 caliber rifle at five tiny targets, the finish can get hairy. Biathlon is a sport where baseline fitness, or the heart rates experienced well below V02-max, are very important, because you must allow your heart rate drop from a near-maximal effort of 165-185 beats-per-minute (bpm) down to 120 bpm in only a few seconds–so that you aim steadily with the 3.5-kilogram (7.7-pound) rifle. Missed shots incur a 150-meter loop penalty, costing competitors about 25 seconds against the field.

In the Sochi sprint biathlon, the gold medal winner was a surprise. Forty-year-old Norwegian Ole Einar Bjørndalen, seeded well down in the field against younger competitors, won his 12th Olympic medal to tie the all-time record of Bjørn Erlend Dæhlie, the legendary Norwegian cross-country star who retired in 2001 after a back injury. In fact it was Dæhlie who set that record for the highest-ever recorded VO2-max of 96. Amazingly, this high number was recorded out of competition without yet reaching his peak fitness. Experts estimate his competition levels could well have been over 100.

As I write this article, more Norwegians are winning medals in men’s and women’s cross-country events, showing the depth of their talent, including some younger Olympians sure to win more medals in the future.

Right now in February 2014, if you want to find the highest average V02-max of any single building earth, look no further than the dormitory of the Norwegian crosscountry skiers and biathletes.

Tom Rodgers is a writer, elite coach, and the author of The Perfect Distance: Triathlete’s Guide to Long-Course Training (Velo Press: 2006) and is a regular contributor to magazines including Inside Triathlon, Lava, and Texas Runner Triathlete. He is a top-ranked over-50 competitor and elite coach for endurance events including the Ironman Triathlon World Championship in Hawaii, the bicycle Race Across America (RAAM), and the Boston Marathon ( Before becoming a full-time writer and coach, he designed extreme physiology experiments and trained astronauts for the International Space Station at NASA in Houston, Texas.

This article originally appeared in the Feb. 21, 2014 issue of the Norwegian American Weekly.

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The Norwegian American is North America's oldest and only Norwegian newspaper, published since May 17, 1889.