By Chris Carmichael
It’s good to be back at a relatively “moderate” elevation of 6,000 feet above sea level after spending the weekend in the even-thinner air up at 10,200-12,600 feet in and around Leadville, Colorado. I was in Leadville to race the Leadville 100 mountain bike race – “The Race Across the Sky” – for the sixth time, and to support and encourage the 178 athletes that Carmichael Training Systems helped prepare for the event. It was a great race and a ton of fun, but both living and exercising above 10,000 feet can be quite difficult – as the pro road racers competing in the USA Pro Cycling Challenge next week will also find out.
The basics of altitude work like this: as you go higher the air becomes less dense, which means the oxygen molecules are more spread out. As a result, when you breathe in and fill your lungs, there are fewer oxygen molecules in that volume of air. Most people from sea level don’t notice any difference at elevations up to about 5,000 feet above sea level, and between 5,000 and 8,000 feet most healthy people feel perfectly fine at rest and might get out of breath more quickly while exercising. The impact of “moderate” elevation is relatively minor because your lungs are very good at extracting oxygen from air, and even as the air gets thinner you’re still able to satisfy the body’s needs.
Once you get above about 8,000 feet, things are a bit different. At these higher elevations people who normally live at sea level get out of breath just walking up a flight of stairs. Your heart rate and breathing rates at rest will be slightly elevated as your body tries to pull more air through the lungs so it can grab the oxygen it wants. And when you exercise you reach your maximum sustainable pace or intensity level much more quickly than at sea level. This means that if you can produce 250 watts of power on the bike at lactate threshold at sea level, at 8,000 feet above sea level you’ll likely reach lactate threshold at about 225 watts (a 10% decline). You’ll be slower riding uphill, or you’ll need to push yourself harder than normal to achieve the same speed you can hold on a climb at sea level.
As you go from 8,000 feet to 10,000 and then to 12,000 feet, your maximum sustainable power output declines even further. Power meters on the bikes – both road bikes and now mountain bikes as well – enable us to measure the extent of the decline. As riders approach the 12,000-foot summits of Columbine Mine (Leadville 100), Cottonwood Pass and Independence Pass (USAPCC), their maximum sustainable power output is about 70-80% of what it is at elevations below 5,000 feet. To put that in perspective consider this: At sea level a pro might have a lactate threshold power output of 350 watts, and a fit weekend warrior of the same bodyweight might have an LT power of 275 watts. At 12,000 feet that pro’s LT power may come all the way down to 245-280 watts; even to the supermen of endurance sports, high altitude is like kryptonite.
It gets worse. Up to now I’ve been talking about max sustainable pace or power. But the worst thing about racing at high elevations is what happens when you dig deep to go even faster – like when you attack to break away or win a mountain-top finish. At lower elevations extreme efforts are difficult, but your body can recover fast because you can get a lot of oxygen to your muscles very quickly. At high elevations, however, extreme efforts exact a much heavier cost. When you push yourself over your sustainable limits for too long, your power output suddenly goes way down, you pant uncontrollably, and slow to a crawl. That can happen at sea level too, but it passes quickly. At high elevations it can take several minutes to recover from hard efforts; by which time you may have completely lost contact with the pack.
Innovations for Exercising/Competing at Altitude
Our understanding of the impact of altitude on performance has improved dramatically in the past 40 or so years (the 1968 Olympics in Mexico City was a major turning point in the science of altitude training). Here are some of the ways LT100 and USAPCC racers cope with the elevation:
- Acclimation: Spending time at higher elevations enables the body to adapt and increase the number of oxygen-carrying red blood cells. This improves your ability to deliver oxygen to the brain and working muscles at all levels of activity, including high-intensity exercise. But true acclimation can take three weeks or more, so it’s often unrealistic to schedule.
- Altitude Training: It is difficult to train and recover optimally at high elevation, so some top athletes strategically plan exposures to altitude (spending a few weeks living and training at higher elevations) throughout the year. This enables them to gain the cardiovascular benefits of acclimating to altitude, and then return to sea level where they can train at higher intensities and recover from training more effectively.
- Acclimatization: (different than acclimation in that it requires proactive steps) Some athletes use specially-designed tents or rooms that simulate the conditions of living/sleeping at high altitude. For some athletes, this can produce an increase in red blood cell count similar to actually spending time at altitude. But the results are highly individual – some people are “responders” and see a benefit, while others do not.
- Hydration: The air at higher elevations is very dry, so sweat evaporates quickly and you lose a lot of fluid moistening/humidifying the air as it enters your lungs. As a result, you dehydrate very quickly at higher elevations. That means less fluid in your blood, which in turn can lead to a higher heart rate because your body has to move the remaining volume faster in order to continue delivering oxygen to working muscles and your brain. If you don’t increase your fluid intake throughout the day you’ll soon have a headache. If you don’t drink enough while exercising, your power output and performance decline very quickly.
- Pacing/Power Meters: Altitude changes racing strategies because some athletes cope with the conditions better than others. Riders who live at high altitudes or who have spent time adapting to high altitude have an advantage, and they can push the pace to put their low-altitude rivals into difficulty. But all riders have to understand where their limits are and be careful about when and how often they exceed those limits. For athletes who don’t have time to adapt to altitude before coming to ride/race at higher elevations, it’s important to be conservative with pacing so you go as fast as you can handle without pushing yourself to the point where you’ll have to suddenly slow down and recover. This is where power meters on the bikes become very useful, because they help riders gauge their efforts.
The USA Pro Cycling Challenge will be broadcast live on Versus every day from August 22-28, and the final day will be broadcast on NBC. Many of the top riders from the 2011 Tour de France (including the entire podium of Cadel Evans, Andy Schleck, and Frank Schleck; as well as American Tom Danielson and others) will all be racing. Here’s something to consider as you’re watching: The summits of the highest mountain passes covered in the Tour de France just barely hit 9,000 feet above sea level. The entire 100 miles of the Leadville 100 are contested at elevations between 9,100 and 12,600 feet. And there will be stages during the USAPCC when the riders will be at between 8,000 and 12,000 feet for the entire day!
Chris Carmichael rode the Tour de France in 1986 with 7-Eleven and recently finished his sixth Leadville 100 mountain bike race. He is CEO and Head Coach of Carmichael Training Systems, the premier destination for coaching, training camps, and performance testing since 2000; and Official Coaching and Camps Partner of Ironman. Follow Chris on Twitter at www.twitter.com/trainright, on Facebook at www.facebook.com/carmichaeltrainingsystems, orwww.trainright.com.