I moved to Boulder, CO in 1993 from living at sea level in the greater Chicagoland area. My training output took a big hit. I remember an early track workout where my 400m repeats were 10+ seconds slower than at sea level while maintaining the same HR. Adjustment eventually came, but it was also incremental.
When I would travel back to sea level for races, I was amazed at how much bigger my lungs felt! It seemed like I could press my effort so much harder and I was definitely reaching higher HR values than I could in Boulder. So, exactly why does higher altitude negatively impact our ability to perform? And, if higher altitudes negatively impact training output then why is it beneficial to live and train at altitude?
Effectively, at higher altitude blood plasma levels decrease, which in turn causes an increase in the density of red blood cells. The drop in blood plasma triggers a decrease in the stroke volume of the heart, which in turn increases heart rate. Due to the increased heart rate, breath rate goes up. All in all, it creates subjective feelings of being out shape, the need to slow down, and gasping for air.
As the body adapts to the higher altitude, typically within 2-4 weeks, blood plasma levels start returning to normal. And, for the most part, training output will approach that of sea level – except for the inherent handicap to performance that accompanies higher altitudes. The dichotomy is that because the air is thinner higher up, it also causes less resistance. This is why some hour record attempts on the velodrome – Eddy Merckx and Miguel Indurain come to mind – were done in Mexico City at 7,400ft. The advantages of less air resistance apparently outweighs the lower oxygen concentration.
Here’s a chart outlining the impact to output at incrementally higher altitudes.
While I’ve been discussing cycling, the effects are similar with both running and swimming – or any aerobic-oriented sport. The main thing to keep in mind is that oxygen, precious O2, is the true fuel of performance. O2-rich blood is what is pumped with each stroke of the heart. As we train or race longer or harder, and the body consumes more O2, it becomes more and more a precious commodity. To compensate for lower O2 saturation in the air – and, thus, what you’re able to suck in with each breath – the body compensates by producing more O2-carrying red blood cells. This is what raises blood plasma levels back to near-normal levels and why performance at altitude starts coming back around.
We need look no further than the fact Grand Tour riders continue to leverage training camps at altitude heading into their key 3-week races to understand that training at altitude brings with it definitive benefits. Top distance runners even take it a step further, embracing the “live high, train low” mantra. Some world class runners live at around 7,000ft in Flagstaff, AZ but drive down to Phoenix at around 2,000ft to perform their key workouts (like track intervals). The premise here is that living high forces the body to produce more O2-carrying red blood cells, and training low allows the athletes to take advantage of all that extra O2 coursing through their veins. The challenge with the “live high, train low” approach is that it requires a lot more time commitment given the extra driving to-and-from workouts. It’s just not practical for anyone who doesn’t train and race for a living.
I’ve thoroughly enjoyed my 2-plus decades in Boulder. The scenery and variety of training is amazing. To me, the benefits of living here extend far beyond whatever the physiological impacts might be. Every time – every single time – I’m exercising outside, I look at my surroundings and wonder aloud at the beauty which surrounds me. That alone makes living at altitude worth it.