title: Alveolar-membrane diffusing capacity limits performance in Boston marathon qualifiers.
abstract: OBJECTIVE
  (1) to examine the relation between pulmonary diffusing capacity and marathon finishing time, and (2), to evaluate the accuracy of pulmonary diffusing capacity for nitric oxide (DLNO) in predicting marathon finishing time relative to that of pulmonary diffusing capacity for carbon monoxide (DLCO).
  
  
  METHODS
  28 runners [18 males, age = 37 (SD 9) years, body mass = 70 (13) kg, height = 173 (9) cm, percent body fat = 17 (7) %] completed a test battery consisting of measurement of DLNO and DLCO at rest, and a graded exercise test to determine running economy and aerobic capacity prior to the 2011 Steamtown Marathon (Scranton, PA). One to three weeks later, all runners completed the marathon (range: 2:22:38 to 4:48:55). Linear regressions determined the relation between finishing time and a variety of anthropometric characteristics, resting lung function variables, and exercise parameters.
  
  
  RESULTS
  In runners meeting Boston Marathon qualification standards, 74% of the variance in marathon finishing time was accounted for by differences in DLNO relative to body surface area (BSA) (SEE = 11.8 min, p<0.01); however, the relation between DLNO or DLCO to finishing time was non-significant in the non-qualifiers (p = 0.14 to 0.46). Whereas both DLCO and DLNO were predictive of finishing time for all finishers, DLNO showed a stronger relation (r(2) = 0.30, SEE = 33.4 min, p<0.01) compared to DLCO when considering BSA.
  
  
  CONCLUSIONS
  DLNO is a performance-limiting factor in only Boston qualifiers. This suggests that alveolar-capillary membrane conductance is a limitation to performance in faster marathoners. Additionally, DLNO/BSA predicts marathon finishing time and aerobic capacity more accurately than DLCO.
authors.affiliation: Human Physiology Laboratory, Marywood University, Scranton, Pennsylvania, United States of America.
authors.forename: Kaleen M
authors.initials: KM
authors.lastname: Lavin
authors.forename: Allison M
authors.initials: AM
authors.lastname: Straub
authors.forename: Kathleen A
authors.initials: KA
authors.lastname: Uhranowsky
authors.forename: James M
authors.initials: JM
authors.lastname: Smoliga
authors.forename: Gerald S
authors.initials: GS
authors.lastname: Zavorsky
mesh_terms: D000328:Adult; D056352:Athletes; D002248:Carbon Monoxide / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D015444:Exercise; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011650:Pulmonary Alveoli / Q000502:physiology*; D011653:Pulmonary Diffusing Capacity; D012420:Running
chemical_list: D002248:Carbon Monoxide