End-tidal CO and ventilation: Novel markers for assessing performance levels in elite long-distance runners.

Well-trained individuals, compared to less well-trained individuals, exhibit a lower minute ventilation (V̇) and higher end-tidal partial pressure of CO (PCO) at a given work rate. This study investigated whether such breathing adaptations seen in well-trained individuals also applied to elite long-distance runners. Forty-one long-distance runners were categorized into high (Long-High, consisting of Tokyo-Hakone College Ekiden [relay marathon] runners and Olympic athletes, n = 23), or low performance-level group (Long-Low, n = 18) according to their race times. Ten middle-distance runners (Middle) also participated in a comparison group. All subjects performed an incremental exercise test on a motorized treadmill until exhaustion. Maximum V̇O and velocity were greater for the Long groups than the Middle group, however these measures were not distinguishable between the Long-High and the Long-Low groups. By contrast, V̇ and PCO were able to identify the Long-High group. Submaximal V̇ were lowest, whilst PCO especially at high running velocities were highest for the Long-High group. This study confirms that breathing patterns with lower V̇ and higher PCO are relevant adaptation markers for assessing endurance race performance in elite long-distance runners.