This is an excerpt from Physiology of Sport and Exercise 6th Edition With Web Study Guide by W. Larry Kenney,Jack Wilmore & David Costill.
Altitude: Optimizing Training and Performance
We have considered the major changes that occur as the human body becomes acclimated to altitude and how these adaptations affect performance at altitude. But is there any advantage to training at altitude to improve performance at sea level? Are there advantages to training at altitude versus training at sea level when one must compete at altitude? And what about the relatively new concept of "live high, train low" to optimize performance?
Does Altitude Training Improve Sea-Level Performance?
Athletes have hypothesized for decades that training under hypoxic conditions, for example in an altitude chamber or by simply breathing low-oxygen gas mixtures, can improve sea-level endurance performance. Since many of the beneficial changes associated with altitude acclimation are similar to those conferred by aerobic training, can combining the two be even more beneficial? Can altitude training improve sea-level performance?
A strong theoretical argument can be made for altitude training. First, altitude training evokes substantial tissue hypoxia (reduced oxygen supply). This is thought to be essential for initiating the conditioning response. Second, the altitude-induced increase in red blood cell mass and hemoglobin content improves oxygen delivery on return to sea level. Although evidence suggests that these latter changes are transient, lasting only several days, in theory this still should provide an advantage for the athlete.
Studying athletes at altitude poses additional problems because they are often unable to train at the same volume and intensity of effort as when at sea level. This was demonstrated in a group of elite female cyclists who performed self-selected maximum power outputs during high-intensity interval training. They completed trials under the following conditions: breathing atmospheric air (normoxia) and breathing a hypoxic gas mixture simulating 2,100 m (6,888 ft). The athletes' sustained (10 min) and short-term (15 s) power outputs at maximal intensity were reduced under hypoxic conditions.4 Training at even higher elevations, where acclimatization effects would be even more beneficial, causes even greater disruptions in training.
In addition, living and training at moderate to high altitude often causes athletes to dehydrate and to lose blood volume and muscle mass. These and other side effects tend to diminish the athletes' fitness and their motivation and tolerance for intense training. As a result, studies are difficult to interpret, but the value of altitude training for optimal sea-level performance has not been validated.
Live High, Train Low
When living and training at altitude, athletes are faced with the problem that the intensity of training is reduced because aerobic capacity and cardiorespiratory function are reduced at altitude. Thus, although athletes gain certain physiological benefits from being at altitude, they lose training adaptations associated with higher intensities of training. One way to get around this problem is to have athletes live at moderate altitude but train at low altitude, where training intensity is not compromised.
Researchers at the Institute for Exercise and Environmental Medicine in Dallas, Texas, conducted a series of studies in the mid-1990s to investigate altitude training for enhancing endurance performance. In one study,11 researchers divided 39 competitive runners into three equal groups: One (the high - low group) lived at moderate altitude (2,500 m, or 8,202 ft) and trained at low altitude (1,250 m, or 4,100 ft); one group (high - high) lived and trained at moderate altitude (2,500 m); and one group (low - low) lived and trained at low altitude (150 m, or 490 ft). Using a 5,000 m time trial as the primary performance outcome measure, the researchers found that the high - low group was the only group to significantly improve their running performance, even though both the high - low and high - high groups increased their O2max values by 5% in direct proportion to their increase in red cell mass. Thus, there appear to be performance benefits from living at moderate altitude but going to lower elevations to maximize training intensity.
Video 13.1 Presents Ben Levine on the physiology behind the live high - train low approach.
This was tested more recently by the same scientists working with a group of 14 elite male and eight elite female runners, with all but two ranked in the U.S. top 50 for their event. These athletes lived at 2,500 m (8,202 ft) and trained at 1,250 m (4,100 ft) over a period of 27 days. Testing was conducted at sea level both the week before and the week after the 27 days of living at altitude. Sea-level 3,000 m time trial performance increased by 1.1% and O2max increased by 3.2% as a result of this intervention.16 Figure 13.8 illustrates the difference in race time performance for both studies, with values expressed as the percentage change before and after altitude exposure. These differences are plotted by the prealtitude race time, expressed as a percentage of the existing U.S. record in the event at the time of the time trial.
Improvement in race time (%) in elite male and female runners16 and collegiate male and female runners11 following 4 weeks of living at altitude but training at 1,250 m (4,100 ft). See the text for details.
Multiple studies have now shown a benefit of living at low altitudes but training at high altitude for increasing sea-level O2max or improving sea-level aerobic performance in elite endurance athletes. These improvements have been linked to an increase in the oxygen-carrying capacity of the blood. Chronic living above 2,500 m (8,202 ft) induces such hematological acclimatization features in most athletes, although there is some variability. A recent study examined whether there is a minimum threshold "living" altitude for improvements in sea-level performance.6 That is, do athletes who live at relatively higher altitudes demonstrate greater performance improvements in a live high - train low setting?
In the study, 48 trained distance runners were randomly assigned to live at one of four altitudes: 1,780 m (5,840 ft), 2,085 m (6,841 ft), 2,454 m (8,051 ft), or 2,800 m (9,186 ft). The athletes all trained together at altitudes between 1,250 m (4,101 ft) and 3,000 m (9,842 ft). Upon return from the live high - train low altitude camp, red blood cell mass and EPO concentrations increased similarly in all four groups, but EPO returned to baseline sooner in the 1,780 m group. Sea-level O2max was improved for all groups as expected (figure 13.9). However, performance on a 3 km (1.9 mi) run at sea level was significantly improved only in the groups that had lived at the middle two altitudes. It appears that increased red blood cell mass is necessary, but not sufficient, for improved performance. Also, there appears to be an optimal living altitude to optimize performance gains in such a setting.
(a) Improvement in 3K time trial (%) and (b) O2max immediately upon return to sea level and 2 weeks later in elite collegiate distance runners6 after 4 weeks of living at one of the four altitudes shown, but training together as a group. See the text for details.
Adapted, by permission, from R.F. Chapman et al., 2014, "Defining the ‘dose' of altitude training: How high to live for optimal sea level performance enhancement," Journal of Applied Physiology 116(6): 595-603.