Sex Differences in Aerobic Fitness in Top-Class Soccer Referees.Castagna Carlo; Bizzini, Mario; D'Ottavio, Stefano; Araújo Póvoas, Susana C.Journal of Strength & Conditioning Research: Post Acceptance: November 14, 2017 doi: 10.1519/JSC.0000000000002292 Original Research: PDF Only Abstract Castagna, C, Bizzini, M, D'Ottavio, S, and Araujo Povoas, SC. Gender differences in aerobic fitness in top-class soccer referees. J Strength Cond Res XX(X): 000-000, 2017-The aim of this study was to assess the aerobic-fitness differences between male and female top-class soccer field referees (FRs). This with the purpose to provide cutoff values useful for training prescription in female FRs. Forty female top-class FRs (age 34.18 +/- 3.50 years and 5 +/- 3.9 years international refereeing experience) and 52 male FRs (age 38.4 +/- 3.3 years and 5 +/- 3.5 years international refereeing experience) candidates in the preliminary open list developed by the FIFA Refereeing Department for the 2014 and 2015 World Cup Tournaments, participated in the study. The FRs were tested for aerobic fitness under laboratory conditions with a progressive speed treadmill test until exhaustion. Female FRs showed to possess, on average, lower (large effect) levels of aerobic fitness and performance compared with their male counterparts. The female FRs' V[Combining Dot Above]O2max (48.1 +/- 4.4 ml[middle dot]kg-1[middle dot]min-1) was 7% (large effect) lower than the male FRs (51.9 ml[middle dot]kg-1[middle dot]min-1). Peak treadmill speed was 11% lower (large effect) in female FRs (16.27 +/- 0.94 vs. 14.64 +/- 0.96 km[middle dot]h-1). The receiver operating characteristic curve analysis enabled cutoff values (47.8 ml[middle dot]kg-1[middle dot]min-1 for V[Combining Dot Above]O2max) that may be used as preliminary cues to guide physiological selection and training prescription in female FRs aiming to officiate male-soccer matches. Only 2.5% of the female FRs showed V[Combining Dot Above]O2max higher than the mean values of male FRs when using the scaled notation (0.68). Female FRs aiming to officiate male competitions should consider training intensities at anaerobic threshold speed (13 km[middle dot]h-1, 95% heart rate max) when developing aerobic fitness. Given the very large sex differences in aerobic performance, strength/power training should be proposed to perspective female top-class FRs. Copyright (C) 2017 by the National Strength & Conditioning Association.