The individual response to training and competition at altitude

Abstract

Performance in athletic activities that include a significant aerobic component at mild or moderate altitudes shows a large individual variation. Physiologically, a large portion of the negative effect of altitude on exercise performance can be traced to limitations of oxygen diffusion, either at the level of the alveoli or the muscle microvasculature. In the lung, the ability to maintain arterial oxyhaemoglobin saturation (SaO₂) appears to be a primary factor, ultimately influencing oxygen delivery to the periphery. SaO₂ in hypoxia can be defended by increasing ventilatory drive; however, during heavy exercise, many athletes demonstrate limitations to expiratory flow and are unable to increase ventilation in hypoxia. Additionally, increasing ventilatory work in hypoxia may actually be negative for performance, if dyspnoea increases or muscle blood flow is reduced secondary to an increased sympathetic outflow (eg, the muscle metaboreflex response). Taken together, some athletes are clearly more negatively affected during exercise in hypoxia than other athletes. With careful screening, it may be possible to develop a protocol for determining which athletes may be the most negatively affected during competition and/or training at altitude.

Keywords: Aerobic Fitness/Vo2 Max; Altitude; Exercise Physiology; Respiratory.

Figure 1

Differences between LoSat and HiSat groups in (left) the change in race pace VO₂ between normoxia and hypoxia (16.3% O₂) and (right) the change in 3000 m race time between sea level and an altitude of 2100 m. Values are means±SE. *Significantly different from HiSat, p≤0.05. Reprinted with permission from Wolter Kluwer Health.

Figure 2

Minute ventilation, ventilatory equivalent for O₂, end-tidal partial pressure of oxygen, and arterial oxyhaemoglobin saturation during graded exercise with placebo (filled circles) and caffeine (8 mg/kg body weight, open squares). Values are means±SE. *Significantly different from placebo at the same percentage of maximal oxygen uptake, p<0.05. Reprinted with permission from Wolters Kluwer Health.

Figure 3

Minute ventilation in normoxia (filled circles) and hypoxia (open circles) at different levels of exercise in non-flow limited (left panel) and flow limited (right panel) groups. Values are means±SE. *Significantly different from normoxia at the same percentage of maximal oxygen uptake, p≤ 0.05. Reprinted with permission from Elsevier.