title: What limits performance during whole-body incremental exercise to exhaustion in humans?
abstract: To determine the mechanisms causing task failure during incremental exercise to exhaustion (IE), sprint performance (10 s all-out isokinetic) and muscle metabolites were measured before (control) and immediately after IE in normoxia (P(IO2) 143 mmHg) and hypoxia (P(IO2): 73 mmHg) in 22 men (22 ± 3 years). After IE, subjects recovered for either 10 or 60 s, with open circulation or bilateral leg occlusion (300 mmHg) in random order. This was followed by a 10 s sprint with open circulation. Post-IE peak power output (W(peak)) was higher than the power output reached at exhaustion during IE (P < 0.05). After 10 and 60 s recovery in normoxia, W(peak) was reduced by 38 ± 9 and 22 ± 10% without occlusion, and 61 ± 8 and 47 ± 10% with occlusion (P < 0.05). Following 10 s occlusion, W(peak) was 20% higher in hypoxia than normoxia (P < 0.05), despite similar muscle lactate accumulation ([La]) and phosphocreatine and ATP reduction. Sprint performance and anaerobic ATP resynthesis were greater after 60 s compared with 10 s occlusions, despite the higher [La] and [H(+)] after 60 s compared with 10 s occlusion recovery (P < 0.05). The mean rate of ATP turnover during the 60 s occlusion was 0.180 ± 0.133 mmol (kg wet wt)(-1) s(-1), i.e. equivalent to 32% of leg peak O2 uptake (the energy expended by the ion pumps). A greater degree of recovery is achieved, however, without occlusion. In conclusion, during incremental exercise task failure is not due to metabolite accumulation or lack of energy resources. Anaerobic metabolism, despite the accumulation of lactate and H(+), facilitates early recovery even in anoxia. This points to central mechanisms as the principal determinants of task failure both in normoxia and hypoxia, with lower peripheral contribution in hypoxia.
authors.affiliation: Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, 35017, Las Palmas de Gran Canaria, Spain.|Research Institute of Biomedical and Health Sciences (IUIBS), Las Palmas de Gran Canaria, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Morales-Alamo
authors.affiliation: Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, 35017, Las Palmas de Gran Canaria, Spain.|Research Institute of Biomedical and Health Sciences (IUIBS), Las Palmas de Gran Canaria, Spain.
authors.forename: José
authors.initials: J
authors.lastname: Losa-Reyna
authors.affiliation: Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, 35017, Las Palmas de Gran Canaria, Spain.|Research Institute of Biomedical and Health Sciences (IUIBS), Las Palmas de Gran Canaria, Spain.
authors.forename: Rafael
authors.initials: R
authors.lastname: Torres-Peralta
authors.affiliation: Research Institute of Biomedical and Health Sciences (IUIBS), Las Palmas de Gran Canaria, Spain.|Department of Sports and Informatics, Pablo de Olavide University, Seville, Spain.
authors.forename: Marcos
authors.initials: M
authors.lastname: Martin-Rincon
authors.affiliation: Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, 35017, Las Palmas de Gran Canaria, Spain.|Research Institute of Biomedical and Health Sciences (IUIBS), Las Palmas de Gran Canaria, Spain.
authors.forename: Mario
authors.initials: M
authors.lastname: Perez-Valera
authors.affiliation: Research Institute of Biomedical and Health Sciences (IUIBS), Las Palmas de Gran Canaria, Spain.|Emergency Medicine Department, Complejo Hospitalario Universitario Insular-Materno Infantil de Las Palmas de Gran Canaria, Avenida Marítima del Sur, s/n, 35016, Las Palmas de Gran Canaria, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Curtelin
authors.affiliation: Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, 35017, Las Palmas de Gran Canaria, Spain.
authors.forename: Jesús Gustavo
authors.initials: JG
authors.lastname: Ponce-González
authors.affiliation: Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, 35017, Las Palmas de Gran Canaria, Spain.|Research Institute of Biomedical and Health Sciences (IUIBS), Las Palmas de Gran Canaria, Spain.|Clinical Genetics Unit, Complejo Hospitalario Universitario Insular-Materno Infantil de Las Palmas de Gran Canaria, Avenida Marítima, del Sur, s/n, 35016, Las Palmas de Gran Canaria, Spain.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Santana
authors.affiliation: Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira s/n, 35017, Las Palmas de Gran Canaria, Spain.|Research Institute of Biomedical and Health Sciences (IUIBS), Las Palmas de Gran Canaria, Spain.
authors.forename: José A L
authors.initials: JA
authors.lastname: Calbet
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000328:Adult; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005221:Fatigue / Q000503:physiopathology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D000860:Hypoxia / Q000378:metabolism / Q000503:physiopathology; D019344:Lactic Acid / Q000378:metabolism; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism / Q000502:physiology; D010101:Oxygen Consumption; D010725:Phosphocreatine / Q000378:metabolism; D055815:Young Adult
chemical_list: D010725:Phosphocreatine; D019344:Lactic Acid; D000255:Adenosine Triphosphate