title: No reserve in isokinetic cycling power at intolerance during ramp incremental exercise in endurance-trained men.
abstract: During whole body exercise in health, maximal oxygen uptake (V̇o2max) is typically attained at or immediately before the limit of tolerance (LoT). At the V̇o2max and LoT of incremental exercise, a fundamental, but unresolved, question is whether maximal evocable power can be increased above the task requirement, i.e., whether there is a "power reserve" at the LoT. Using an instantaneous switch from cadence-independent (hyperbolic) to isokinetic cycle ergometry, we determined maximal evocable power at the limit of ramp-incremental exercise. We hypothesized that in endurance-trained men at LoT, maximal (4 s) isokinetic power would not differ from the power required by the task. Baseline isokinetic power at 80 rpm (Piso; measured at the pedals) and summed integrated EMG from five leg muscles (ΣiEMG) were measured in 12 endurance-trained men (V̇o2max = 4.2 ± 1.0 l/min). Participants then completed a ramp incremental exercise test (20-25 W/min), with instantaneous measurement of Piso and ΣiEMG at the LoT. Piso decreased from 788 ± 103 W at baseline to 391 ± 72 W at LoT, which was not different from the required ramp-incremental flywheel power (352 ± 58 W; P > 0.05). At LoT, the relative reduction in Piso was greater than the relative reduction in the isokinetic ΣiEMG (50 ± 9 vs. 63 ± 10% of baseline; P < 0.05). During maximal ramp incremental exercise in endurance-trained men, maximum voluntary power is not different from the power required by the task and is consequent to both central and peripheral limitations in evocable power. The absence of a power reserve suggests both the perceptual and physiological limits of maximum voluntary power production are not widely dissociated at LoT in this population.
authors.affiliation: School of Biomedical Sciences and Multidisciplinary Cardiovascular Research Centre, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom; c.ferguson@leeds.ac.uk.
authors.forename: Carrie
authors.initials: C
authors.lastname: Ferguson
authors.affiliation: School of Biomedical Sciences and Multidisciplinary Cardiovascular Research Centre, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom;
authors.forename: Lindsey A
authors.initials: LA
authors.lastname: Wylde
authors.affiliation: School of Biomedical Sciences and Multidisciplinary Cardiovascular Research Centre, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom;
authors.forename: Alan P
authors.initials: AP
authors.lastname: Benson
authors.affiliation: Rehabilitation Clinical Trials Center, Division of Respiratory and Critical Care Physiology and Medicine, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California; and School of Exercise and Nutritional Sciences, San Diego State University, San Diego, California.
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Cannon
authors.affiliation: School of Biomedical Sciences and Multidisciplinary Cardiovascular Research Centre, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom; Rehabilitation Clinical Trials Center, Division of Respiratory and Critical Care Physiology and Medicine, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California; and.
authors.forename: Harry B
authors.identifier: http://orcid.org/0000-0002-7884-0726
authors.initials: HB
authors.lastname: Rossiter
mesh_terms: D015308:Anaerobic Threshold; D001642:Bicycling / Q000502:physiology*; D004576:Electromyography; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018763:Muscle Fatigue; D064797:Physical Conditioning, Human / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D055815:Young Adult
keywords: V̇o2max; central fatigue; electromyography; exercise tolerance; peripheral fatigue