title: Fatigue associated with prolonged graded running.
abstract: Scientific experiments on running mainly consider level running. However, the magnitude and etiology of fatigue depend on the exercise under consideration, particularly the predominant type of contraction, which differs between level, uphill, and downhill running. The purpose of this review is to comprehensively summarize the neurophysiological and biomechanical changes due to fatigue in graded running. When comparing prolonged hilly running (i.e., a combination of uphill and downhill running) to level running, it is found that (1) the general shape of the neuromuscular fatigue-exercise duration curve as well as the etiology of fatigue in knee extensor and plantar flexor muscles are similar and (2) the biomechanical consequences are also relatively comparable, suggesting that duration rather than elevation changes affects neuromuscular function and running patterns. However, 'pure' uphill or downhill running has several fatigue-related intrinsic features compared with the level running. Downhill running induces severe lower limb tissue damage, indirectly evidenced by massive increases in plasma creatine kinase/myoglobin concentration or inflammatory markers. In addition, low-frequency fatigue (i.e., excitation-contraction coupling failure) is systematically observed after downhill running, although it has also been found in high-intensity uphill running for different reasons. Indeed, low-frequency fatigue in downhill running is attributed to mechanical stress at the interface sarcoplasmic reticulum/T-tubule, while the inorganic phosphate accumulation probably plays a central role in intense uphill running. Other fatigue-related specificities of graded running such as strategies to minimize the deleterious effects of downhill running on muscle function, the difference of energy cost versus heat storage or muscle activity changes in downhill, level, and uphill running are also discussed.
authors.affiliation: Salomon SAS, Amer Sports Innovation and Sport Sciences Laboratory, 74996, Annecy, France.|Inter-universitary Laboratory of Human Movement Biology (EA 7424), University Savoie Mont Blanc, 73376, Le Bourget-du-Lac, France.
authors.forename: Marlene
authors.initials: M
authors.lastname: Giandolini
authors.affiliation: Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, 2500 University Dr NW, Calgary, AB, T2N 1N4, Canada.|CeRiSM, Research Center for Sport, Mountain and Health, University of Verona, Rovereto, TN, Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Vernillo
authors.affiliation: Inter-universitary Laboratory of Human Movement Biology (EA 7424), University Savoie Mont Blanc, 73376, Le Bourget-du-Lac, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Samozino
authors.affiliation: Salomon SAS, Amer Sports Innovation and Sport Sciences Laboratory, 74996, Annecy, France.|Inter-universitary Laboratory of Human Movement Biology (EA 7424), University Savoie Mont Blanc, 73376, Le Bourget-du-Lac, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Horvais
authors.affiliation: Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, 2500 University Dr NW, Calgary, AB, T2N 1N4, Canada.
authors.forename: W Brent
authors.initials: WB
authors.lastname: Edwards
authors.affiliation: LAMHESS, Université Côte d'Azur, Nice, France.
authors.forename: Jean-Benoît
authors.initials: JB
authors.lastname: Morin
authors.affiliation: Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, 2500 University Dr NW, Calgary, AB, T2N 1N4, Canada. gmillet@ucalgary.ca.
authors.forename: Guillaume Y
authors.initials: GY
authors.lastname: Millet
mesh_terms: D006801:Humans; D009119:Muscle Contraction / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D012420:Running / Q000502:physiology*; D013647:Task Performance and Analysis
keywords: Biomechanics; Downhill; Energy cost; Fatigue; Level; Neuromuscular function; Running; Tissue damage; Uphill