Those heading to Ironman Arizona and Ironman Florida from cooler environments should consider strategies for acclimating to heat and humidity for the race. IMAZ folks living in cool climates should be over-dressing now. See strategies in the two-part column, Acclimating to Heat and Humidity.
In the last blog I mentioned that I would cover why I was able to ride within my lactate threshold heart rate range for two hours and forty-five minutes. That’s not possible – is it?
Recapping some of the altitude specifics, the mainstay of my training over the summer was directed at doing mountain bike races between 8 and 11 hours long and at altitudes between 9,000 and 12,600 feet. I live atroughly 5,000 feet. The September race where I accumulated near three hours at lactate threshold intensity was at altitudes between 3,000 and 6,000 feet.
Heart rate increases in response to higher altitudes – but you cannot maintain the same speed or power output for that given heart rate at increased altitude. This means that lactate threshold heart rate at increased altitude is lower than your home base.
For a given speed or power output at a lower-than-your-home-base altitude, the corresponding heart rate will be lower. (Assuming temperature and humidity conditions are similar.)
To know my actual heart rate training zones for all ofthe corresponding altitudes where I raced this summer, I would need to do a test at each location. Since that is logistically not possible for me, I use the same data collection zones for all altitudes and adjust accordingly – I raced according to my rating of perceived exertion (RPE) for the lower altitude event. This means the data for my race at a lower altitude is not really all within an accurate lactate threshold zone. So no, I didn’t spend near three hours at lactate threshold.
Also recall within the altitude columns that you can produce higher speeds and more power output at lower altitudes. (The reason why the Olympians living in Colorado Springs train with supplemental oxygen sources for sea level racing.)
Sans actual power data, I believe I did not have the training to tolerate the power outputs I was generating at the lower altitude race. If the neuromuscular and metabolic systems have not been trained for the speed and power outputs (duration and intensity) possible at lower altitudes, then I believe there is a possibility of cramping.
Several years ago a buddy and I decided to train for a trail run. As I mentioned in yesterday’s blog, we live at roughly 5,000 feet and the trail run would be at elevations between 4,000 and 8,500 feet. As we began training in the mountains at higher elevations, we both noticed a marked shortness of breath. We believed it was the altitude affecting us.
As we continued training, we both noticed that it seemed that the altitude was bothering us less and less – even though we had just a few hours of exposure each week. Because most literature supports a “stay at altitude for three weeks” format of altitude acclimatization, I wondered if anyone had looked at intermittent exposure.
I contacted Dr. Randy Wilber, head physiologist for the U.S.Olympic Training Center and asked if he had seen anything on intermittent exposure. He said he hadn’t. I asked his opinion on the experience we had with our once-per-week format and he said that though there’s no evidence, he had to believe that some expose is better than none and does offer some form of adaptation.
When I was training for the trail run, I had no way to easily measure whether my weekly exposure was beneficial or not.
As I mentioned in yesterday’s blog, I purchased a pulse oximeter in 2010. Since that time, I’ve taken samples of oxygen saturation (SPO2) at 5,000 feet and at 9,100 feet for myself. Know that this is a sample size of one and the experiment was far from controlled and scientific. That written, here’s what I’ve found:
SPO2 at home, 5,000 feet runs 98 most of the time
SPO2 at 9,100 feet runs 92 if I have not been at altitude for over four weeks
If I have 24 to 72 hours of exposure to 9,100 feet every three weeks, SPO2 runs at 96 (know that I sleep at 9,100 and exercise is most often at higher altitudes)
At the end of last summer, when altitude exposure at 9,100 was more frequent than every 21 days, my SPO2 would be between 97 and 98
In summary, for me, intermittent exposure to altitude does help SPO2 and I can feel the difference as well. It's an advantage for me. Though I didn’t collect as much data on pulse rate, I did see pulse rate drop on a track similar to the rise in SPO2. This is good - more oxygen saturation for less work for my heart.
If you wonder what’s happening to your oxygen saturation when you travel to the mountains for fun, training or racing I suggest picking up a pulse oximeter and taking some measurements. You can get a quality device for around $50.