Purpose: Despite interest in the possibility of females outperforming males in ultraendurance sporting events, little is known about the sex differences in fatigue during prolonged locomotor exercise. This study investigated possible sex differences in central and peripheral fatigue in the knee extensors and plantar flexors resulting from a 110-km ultra-trail-running race.
Methods: Neuromuscular function of the knee extensors and plantar flexors was evaluated via transcranial magnetic stimulation (TMS) and electrical nerve stimulation before and after an ultra-trail-running race in 20 experienced ultraendurance trail runners (10 females and 10 males matched by percent of the winning time by sex) during maximal and submaximal voluntary contractions and in relaxed muscle.
Results: Maximal voluntary knee extensor torque decreased more in males than in females (−38% vs −29%, P = 0.006) although the reduction in plantar flexor torque was similar between sexes (−26% vs −31%). Evoked mechanical plantar flexor responses decreased more in males than in females (−23% vs −8% for potentiated twitch amplitude, P = 0.010), indicating greater plantar flexor peripheral fatigue in males. Maximal voluntary activation assessed by TMS and electrical nerve stimulation decreased similarly in both sexes for both muscle groups. Indices of knee extensor peripheral fatigue and corticospinal excitability and inhibition changes were also similar for both sexes.
Conclusions: Females exhibited less peripheral fatigue in the plantar flexors than males did after a 110-km ultra-trail-running race and males demonstrated a greater decrease in maximal force loss in the knee extensors. There were no differences in the magnitude of central fatigue for either muscle group or TMS-induced outcomes. The lower level of fatigue in the knee extensors and peripheral fatigue in the plantar flexors could partly explain the reports of better performance in females in extreme duration running races as race distance increases.
1Laboratoire de Physiologie de l’Exercice, Université de Lyon, Saint-Etienne, FRANCE; 2Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, CANADA; 3Laboratoire de Physiologie de l’Exercice, Université de Savoie, Chambéry, FRANCE; 4Centre Hospitalier Universitaire de Saint-Etienne, Centre Référent Maladies Neuromusculaires Rares Rhône-Alpes, Unité de Myologie, Saint-Etienne, FRANCE; 5Département de Biochimie, Centre de Biologie et de Pathologie Est, Groupement Hospitalier Est, Hospices Civils de Lyon, Bron, FRANCE; 6Département d’Anesthésie-Réanimation, Service de Réanimation Polyvalente B, Hôpital Nord, CHU de Saint-Étienne, Université Jean-Monnet de Saint-Étienne, Université de Lyon, Saint-Priest-en-Jarez, FRANCE; 7HP2 Laboratory, Université Grenoble Alpes, Grenoble, FRANCE; 8INSERM, U1042, Grenoble, FRANCE; and 9Laboratoire des Adaptations Métaboliques à l’Exercice en Conditions Physiologiques et Pathologiques, Université Blaise Pascal, Clermont Université, Clermont Ferrand, FRANCE
Address for correspondence: John Temesi, Ph.D., Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, 2500 University Dr NW, Calgary, Alberta, Canada T2N 1N4; E-mail: email@example.com.
Submitted for publication May 2014.
Accepted for publication October 2014.