Altitude training: turn up the heat for enduring benefits

Although many readers won’t remember them, something special marked out the 1968 Olympic Games, which was held in Mexico City. Competitors in the sprint and jump events almost always excelled and many records were broken, while athletes competing in endurance events struggled, with many failing to come close even to their personal best. Of the 26 Olympic and world athletics records set, only one came in a track event over 800 metres.

The reason for these unusual results was simple; at approximately 2,240 meters (7,350 feet) above sea level, Mexico City is one of the highest capital cities in the world. At this altitude, air is 20% thinner, meaning there is 20% less oxygen to fuel endurance activity, which explains why the distance athletes struggled so much. Meanwhile, the thinner air was a positive benefit to athletes such as track and cycling sprinters who needed to overcome air resistance, but could do so without resorting to energy delivered by the aerobic (oxygen dependent) energy system.

Altitude and endurance

Although sports physiologists were previously aware of the ‘altitude effect’, it was only after the 1968 Olympic Games when the effects of altitude on endurance performance were hammered home. And because it was known that the human body tends to adapt to and compensate for its environment, there soon followed a growing interest in the use of moderate altitude training – ie at altitudes of approximately 2000-3000 metres (6,800-10,000ft) - to improve competition performance both at altitude and sea level see figure 1). In particular, research shows that when endurance athletes are exposed acutely to moderate altitude, a number of physiological responses occur that can initially comprise performance at altitude but which over time can lead to positive adaptations, conferring an advantage when returning to sea level. These include⁽¹⁾:

·        Neurological and muscular adaptations that improve oxygen delivery to and utilization in the muscles.

·        An increased training stimulus for the same workload due to the low-oxygen environment.

·        Improved blood haemoglobin levels (the component in red blood cells that transports oxygen in the blood) and red blood cell numbers.

Figure 1: How high is high enough for the altitude effect?