Do Faster Ultra-endurance Runners Have A Pulmonary Phenotype?

Abstract

PURPOSE: The cardiopulmonary system of ultramarathon runners is exposed to prolonged periods of increased cardiac output and ventilation during exercise, which can stress the alveolar-capillary membrane. In order to determine if an adaptive pulmonary phenotype exists in ultramarathon runners, we tested the hypothesis that individuals who can sustain a faster race pace have superior pulmonary function and lung diffusing capacity. METHODS: Twenty-seven runners were assessed prior to a 100km ultramarathon at two different races (Hong Kong 100, N=19, CCC, N=8). Forced vital capacity (FVC) and forced expiratory volume in 1s (FEV1) were assessed via spirometry. Lung diffusing capacity for carbon monoxide (DLCO) and nitric oxide (DLNO) were measured using a single-breath technique at rest and during 3 stages of low level exercise. The DLNO/DLCO was calculated to assess the relative contribution of membrane conductance to capillary blood volume. The cohort was split into a faster group with an average finish time under 15 hours and a slower group with an average finish time above 21 hours to compare differences in pulmonary function. RESULTS: Baseline FVC and FEV1 were not different in the faster runners (FVC=5.2±0.5L; FEV1=4.2±0.5L) compared to the slower runners (FVC=5.2±1.1L; FEV1=4.1±0.8L), and did not differ from normative values, with overall percent predicted FVC and FEV1 at 105% and 92%, respectively. DLCO and DLNO did not differ between groups (fast, DLCO=33.2±6.0mmHg, DLNO=160.2±26.0mmHg; slow, DLCO=30.2±5.5mmHg, DLNO=155.2±27.6mmHg), however the ratio of DLNO/DLCO was lower in the faster group at rest (4.9 vs. 5.2, p=0.018) and during exercise (stage3: 4.9±0.2 vs.5.3±0.4, p<0.01). CONCLUSIONS: Resting lung function was not enhanced in faster runners, however the altered DLNO/DLCO ratio with light exercise suggests a greater relative contribution of capillary blood volume to membrane conductance might be associated with ultraendurance performance.