As altitude increases, a hypobaric environment exists. At this low pressure, the air is less dense and so there are fewer oxygen molecules in a given volume of air. With less oxygen being delivered to the working muscles, the body compensates through a hormone-mediated increase in the volume of red blood cells (RBC) that carry the oxygen in the blood. The extent to which the hormone, erythropoietin (EPO), is secreted from the kidneys is relative to the elevation in altitude. Nevertheless, as the body strives for more oxygen due to the thinner air, the rate and depth of breathing increases and together with the accelerated metabolism, this has been shown to reduce endurance performance while at altitude (Sutton, 1993). On return from training at moderate altitude however, the elevated RBC volume improves the aerobic transport system, enabling the athlete to experience superior oxygen delivery and hence, endurance ability (Rusko, 1996). Optimum height for observing this ergogenic effect on endurance performance is between 1800 and 3000 m (Maxwell, 2000); any higher and the risk of detraining takes place due to the exercise intensity being significantly reduced.
Whilst the physiological responses of altitude exposure have been examined in relation to tasks that are predominantly aerobic, little attention has been given to the effect that altitude has upon high intensity, intermittent exercise. Bouts of sprint exercise that are interspersed with periods of submaximal exercise and passive rest are known to have a significant contribution from aerobic metabolism (Bogdanis et al., 1996). Therefore, intuitively one might expect that any elevation in RBC volume that occurs from altitude exposure, would lead to an improved oxygen transport system and recovery between repeated bouts of sprinting. Indeed, Nummela and Rusko (2000) found 400-m performance, an event that significantly relies upon aerobic metabolism, to be improved following 10 days of exposure to normobaric hypoxic conditions. When considering the popularity and dominance of team sports around the world, it seems somewhat surprising that few studies have explored the responses of altitude exposure and its possible ergogenic effect towards intermittent high intensity exercise. Further, there is little empirical evidence to support or refute the hypothesis of high altitude exposure (i.e. > 3000 m), that greatly stimulates EPO, having a positive influence upon intermittent high intensity exercise. It is conceivable to think that performing exercise that is not sport specific, but is at a high enough altitude may still result in performance enhancing responses during repeated sprint exercise due to a hyper-stimulation of EPO.
PURPOSE OF STUDY:
This investigation aims to examine the physiological parameters important to intermittent sprint exercise before and after exposure to high altitude during which non-specific, low-intensity exercise will be performed.