title: Rate of utilization of a given fraction of W' (the curvature constant of the power-duration relationship) does not affect fatigue during severe-intensity exercise.
abstract: What is the central question of this study? Does the rate of utilization of W' (the curvature constant of the power-duration relationship) affect fatigue during severe-intensity exercise? What is the main finding and its importance? The magnitude of fatigue after two severe-intensity exercises designed to deplete the same fraction of W' (70%) at two different rates of utilization (fast versus slow) was similar after both exercises. Moreover, the magnitude of fatigue was related to critical power (CP), supporting the contention that CP is a key determinant in fatigue development during high-intensity exercise. Thus, the CP model is a suitable approach to investigate fatigue mechanisms during high-intensity exercise. The depletion of W' (the curvature constant of the power-duration relationship) seems to contribute to fatigue during severe-intensity exercise. Therefore, the aim of this study was to determine the effect of a fast versus a slow rate of utilization of W' on the occurrence of fatigue within the severe-intensity domain. Fifteen healthy male subjects performed tests to determine the critical power, W' and peak torque in the control condition (TCON ) and immediately after two fatiguing work rates (THREE and TEN) set to deplete 70% W' in either 3 (TTHREE ) or 10 min (TTEN ). The TTHREE and TTEN were significantly reduced (F = 19.68, P = 0.01) in comparison to TCON . However, the magnitude of reduction in peak torque (TTHREE  = -19.8 ± 10.1% versus TTEN  = -16.8 ± 13.3%) was the same in the two fatiguing exercises (t = -0.76, P = 0.46). There was a significant inverse relationship between the critical power and the reduction in peak torque during both THREE (r = -0.49, P = 0.03) and TEN (r = -0.62, P = 0.02). In contrast, the W' was not significantly correlated with the reduction in peak torque during both THREE (r = -0.14, P = 0.33) and TEN (r = -0.30, P = 0.10). Thus, fatigue following severe-intensity exercises performed at different rates of utilization of W' was similar when the same work was done above the critical power (i.e. same amount of W' used).
authors.affiliation: Physical Effort Laboratory, Sports Center, Federal University of Santa Catarina, Florianópolis, Brazil.
authors.forename: Kristopher Mendes
authors.initials: KM
authors.lastname: de Souza
authors.affiliation: Centre for Sport and Exercise Science and Medicine, University of Brighton, Eastbourne, UK.
authors.forename: Jeanne
authors.initials: J
authors.lastname: Dekerle
authors.affiliation: Physical Effort Laboratory, Sports Center, Federal University of Santa Catarina, Florianópolis, Brazil.
authors.forename: Paulo Cesar do Nascimento
authors.initials: PC
authors.lastname: Salvador
authors.affiliation: Physical Effort Laboratory, Sports Center, Federal University of Santa Catarina, Florianópolis, Brazil.
authors.forename: Ricardo Dantas
authors.initials: RD
authors.lastname: de Lucas
authors.affiliation: Physical Effort Laboratory, Sports Center, Federal University of Santa Catarina, Florianópolis, Brazil.
authors.forename: Luiz Guilherme Antonacci
authors.initials: LG
authors.lastname: Guglielmo
authors.affiliation: São Paulo State University, Human Performance Laboratory, Rio Claro, Brazil.
authors.forename: Camila Coelho
authors.initials: CC
authors.lastname: Greco
authors.affiliation: São Paulo State University, Human Performance Laboratory, Rio Claro, Brazil.
authors.forename: Benedito Sérgio
authors.initials: BS
authors.lastname: Denadai
mesh_terms: D000328:Adult; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test / Q000379:methods; D017079:Exercise Tolerance / Q000502:physiology*; D005221:Fatigue / Q000503:physiopathology*; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology; D010807:Physical Endurance / Q000502:physiology*