So, there has been a steady interest among endurance athletes in the benefits of living or living and training at altitude. Runners, cyclists and triathletes all seek out places where they can live and train above sea level some odd thousands of feet in order to gain a competitive advantage by stimulating their body to produce more red blood cells and thereby increase their total capacity for consuming oxygen.
But, personally having experience living at sea level and doing some racing and training at altitude each year, I question the extent to which living at altitude might benefit endurance athletes, or to what extent it would benefit different athletes individually. Largely, I wonder because not all athletes give the same account of their experiences at altitude. Some, for example, hyperventilate easily when exercising hard at altitude whereas others appear to have more comfortable, controlled breathing even when apparently exhausting themselves to a similar extent. Some experience interrupted, abbreviated sleep patterns and constant headaches or even nausea, while others simply don’t. Some people start to experience some symptoms of altitude sickness at 8,000-10,000 feet while others are totally fine, except for a universally similar loss of aerobic performance because of limited oxygen supply.
Basically, some of my experience and observation of fellow athletes at altitude, combined with reading on the subject, make me suspect that people’s response to altitude may be heavily influenced by what composition of fast- and slow-twitch muscle they have, and perhaps also by the fitness of their breathing muscles, among other things, no doubt…
For example, having a greater proportion of fast-twitch muscle fibers presumably allows an athlete to create a greater level of oxygen debt more quickly than someone with a majority of slow twitch fibers, which will take longer to recover from at altitude than at sea level. The person with a majority of slow twitch fibers probably gains something of an advantage at altitude because they are less capable of creating an oxygen debt that they will have to repay with a reduction of effort. Likewise, people who have more powerful breathing muscles, the diaphragm most important among them, breathe more easily and remain more relaxed than others. According to Alison McConnell, an expert on breathing and exercise, the oxygen demands of exercise, the cardiac output during exercise, breathing requirement, and perceived effort of individuals with inspiratory muscle training is significantly reduced compared to controls. (Check out her book.)
Also, I’ve long suspected that living and training at altitude might be a liability because of a reduction in total workload while exercising. To me, this suggests that your heart and lungs might be getting a better workout at altitude, but that your working muscles are getting less of a workout (they get less oxygen and can do less work). This is the reason that some people advocate for living at altitude and training at sea level, which makes sense. But at the same time, if you’re training hard at sea level, you may recover better between workouts at sea level, though not necessarily. It has occurred to me that doing hard training blocks at sea level followed by easier blocks of training at altitude could be a good way to stimulate changes in your blood, but also get the benefits of higher workloads at sea level and possibly faster recovery.
It also seems generally inconvenient, costly or even impossible for most people to live at altitude and train at sea level on a day-to-day basis. But, though still inconvenient, it may be easier and less costly for some to live and train at altitude, say, one or two weeks each month, and spend the rest of the time at sea level. Whatever the case may be, it seems doubtful that training at altitude can be the best for anyone that wants to be able to perform high-intensity bursts of activity, whereas it may be fine for people whose exercise demands are almost always at or below their lactate threshold (however you want to define that), like marathon runners, for example.
Generally, there is substantial evidence in favor of enhanced aerobic performance by individuals that live and train at altitude and those that live altitude but train at sea level. I think that it would be well worth while to investigate whether similar or greater gains could be had by living at altitude intermittently. Still, for the vast majority of endurance athletes (i.e. all but the few elites with nothing on their minds but training), it’s probably better to invest time and money into good nutrition, good sleep, and a sound approach to training. Only after all of those bases are covered, should anyone worry about looking into buying an altitude tent or moving, and if ever considered, those methods should not compromise any of those other key elements (i.e. diet, rest, and proper training).