ORIGINAL ARTICLES  EXERCISE PHYSIOLOGY AND BIOMECHANICS 

The Journal of Sports Medicine and Physical Fitness 2016 July-August;56(7-8):857-63

Copyright © 2016 EDIZIONI MINERVA MEDICA

lingua: Inglese

Neuromuscular changes associated with superior fatigue resistance in African runners

Yolande X. HARLEY ¹, Jordan SANTOS-CONCEJERO ², Alan ST. CLAIR GIBSON ³, Hugh MULLANY ⁴, Karen A. SHARWOOD ¹, Sacha J. WEST ¹, Timothy D. NOAKES ¹, Malcolm COLLINS ¹, Ross TUCKER ³ ✉

¹ UCT/MRC Research Unit for Exercise Science and Sports Medicine, Department of Human Biology, University of Cape Town, Cape Town, South Africa; ² Department of Physical Education and Sport, University of the Basque Country, Vitoria-Gasteiz, Spain; ³ School of Medicine, University of the Free State, Bloemfontein, South Africa; ⁴ Mullany Engineering Consultancy Ltd., Blackrock, Co. Dublin, Ireland

BACKGROUND: An enhanced ability to resist fatigue has been proposed as one of African runners’ performance superiority sources, although their fatigue resistance during sustained non-running-specific activities remain unclear. This study aimed to compare fatigue resistance during sustained isometric exercise between performance-matched African and European runners.
METHODS: Thirty long-distance runners (16 African, 14 European) performed submaximal fatiguing sustained isometric knee extensions. Rectus femoris electromyographic (EMG) activity was measured, and the muscle was electrically stimulated to contract at the beginning and end of the test.
RESULTS: Time to task failure was greater for African than European runners (269±115 vs. 193±52 s, P=0.002; effect size [ES]=0.85, large effect). During the test, EMG amplitude increased less over time (P=0.031), and the left shift in the EMG frequency spectrum was less over time for the African runners (P<0.001). In addition, there was a lower relative reduction in stimulated force output from the first to the second stimulation in African runners (17.75±14.95 vs. 37.89±14.78%, P=0.006; ES=1.35; large effect).
CONCLUSIONS: These findings of greater fatigue resistance during non-running-specific activity and the associated muscle recruitment profile may contribute to the understanding of the physiology underlying endurance performance in African runners.