End-tidal CO2 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_E) and higher end-tidal partial pressure of CO₂ (P_ETCO₂) 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 V̇O₂ 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_E and P_ETCO₂ were able to identify the Long-High group. Submaximal V̇_E were lowest, whilst P_ETCO₂ especially at high running velocities were highest for the Long-High group. This study confirms that breathing patterns with lower V̇_E and higher P_ETCO₂ are relevant adaptation markers for assessing endurance race performance in elite long-distance runners.