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In Speed Skating, Other Sports, Air Resistance Plays A Big Role

Tue, 2014-02-11 17:06 -- ssuchy
Feb 11 2014 - 5:00pm
By: Chris Gorski, Inside Science, Senior Editor
Canada Womens 500m Speed Skating - Richmond Olympic Oval - British Columbia | Kris Krug via flickr, http://bit.ly/1ctvYZi

Each sport has its own challenges. And at the highest levels, such as at the Olympics, things that seem like they should be little factors really add up. Things like air resistance and clothing can separate one athlete from another, or even force the athlete to adapt to a new situation, rejecting the familiar feel of a honed technique, built up in muscle memory.

Speed skating is a good example. As explained in yesterday's Inside Science story, the altitude at which a speed skating event is held plays a large factor in the time that it takes to complete the race. In a venue in Sochi, which is near sea level, the air resistance is much greater than it is at a few thousand feet above sea level. This is why all current world records, men's and women's, were set at tracks in Calgary, Alberta, and Salt Lake City, Utah.

But reducing air resistance is a many-headed monster.

For example, the U.S. speed skating team is wearing advanced suits from Under Armour, honed in hundreds of hours of wind tunnel tests, as described at length in the New Scientist, the Washington Post, and the Globe and Mail.

Air resistance also influences the skaters' posture.

The Crouch

Robert Chapman, an exercise physiologist at Indiana University, in Bloomington, told Inside Science that the deeply bent, compact tuck position speed skaters use while racing is very uncomfortable. They use that position in order to reduce their air resistance. But, they have to find a way to be able to skate and move their legs at the same time.

"Think about being in a squat, with your leg muscles contracted like they do for 10, 15, 18 minutes. It's an incredibly uncomfortable position to be in, but they've trained for it and it ends up where they can end up doing what they do at amazing levels," said Chapman.

The crouch that speed skaters maintain during a race is so extreme that they reduce blood flow to their legs, Chapman said. "[I]t's only when the leg is extended … and the muscles relax, that basically blood is allowed to flow in… It's incredible to look at how much that blood flow gets cut off, but that's the position they have to be in to minimize drag."

In fact, training on the ice is so intense that speed skaters do much of their training somewhere else. In a Wall Street Journal story, U.S. speed skater Brian Hansen said that overtraining stresses his back and that he "rarely spends more than 75 minutes on the ice on a given day." Much of his training time is spent on a bike.

"[S]peed skaters, even though they could be on ice all year around, they don't because it's just so demanding to be in the skating position and go around a curve at 50 kilometers per hour [about 31 mph] that they just can't do that all the time," said Stephen Seiler, an exercise physiologist at the University of Agder in Kristiansand, Norway.

Speed Differences

Like so many Winter Olympic sports, speed skating is highly technical. While the athletes are in the crouch, they need to keep track of where they are on the course. Speeding through the turns can be difficult. Now imagine that the same full-out effort results in a different speed based on the altitude of the competition venue.

Male speed skaters average more than 30 mph in all but the longest races, and top women often average 30 mph for sprints. At sea level they might travel 0.5 mph less, or even slower, than they would at a track in places such as Calgary and Salt Lake City, due primarily to the increased air resistance. That means the skater might be going more than 2 percent slower at lower elevations. This could create some difficulty for athletes who train at a higher elevation than at Sochi.

"They're going to take those turns at different speeds. One is the speed that they practice at if they've been at altitude and the other is the speed they're going to have when they're at sea level," said Chapman. "Now their speed is going to be a little slower, so their timing is going to end up being just a little bit different." From a motor control or neuromuscular standpoint, they have probably spent time practicing at the competition altitude to avoid errors, he added.

However, many of them probably trained at high altitude, as do many endurance athletes, including cross country skiers, in order to encourage their bodies to produce more red blood cells.

"That's helpful for endurance exercise because now you can deliver more oxygen to the muscles, both at altitude and at sea level," said Chapman. "It's a very, very large effect on performance."

Air Resistance Beyond The Oval

Effects due to air resistance can even extend to sports where speed is not the main objective. Chapman mentioned figure skating and ski jumping in particular. A figure skater encounters air resistance when trying to make a triple or quadruple jump. Chapman said that rotational speed of a figure skater might be slower at sea level, not much more than a couple of degrees, but he said that being off by that much can make a difference.

The ski jump at the 2014 Winter Olympics is not in Sochi itself, but about 40 miles away, at the mountain venue near Krasnaya Polyana, so jumpers aren't facing the same air resistance as they would at sea level. Air resistance determines the optimum angle for a ski jumper as he or she leans over the skis in order to best form a wing-shape during their flight. The difference between jumping at sea level and at 7,000 feet is more than four degrees of lean, said Chapman.

Chris Gorski is a Senior Editor for Inside Science and tweets at @c_gorski.

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