title: Creatine ingestion augments dietary carbohydrate mediated muscle glycogen supercompensation during the initial 24 h of recovery following prolonged exhaustive exercise in humans.
abstract: Muscle glycogen availability can limit endurance exercise performance. We previously demonstrated 5 days of creatine (Cr) and carbohydrate (CHO) ingestion augmented post-exercise muscle glycogen storage compared to CHO feeding alone in healthy volunteers. Here, we aimed to characterise the time-course of this Cr-induced response under more stringent and controlled experimental conditions and identify potential mechanisms underpinning this phenomenon. Fourteen healthy, male volunteers cycled to exhaustion at 70 % VO2peak. Muscle biopsies were obtained at rest immediately post-exercise and after 1, 3 and 6 days of recovery, during which Cr or placebo supplements (20 g day(-1)) were ingested along with a prescribed high CHO diet (37.5 kcal kg body mass(-1) day(-1), >80 % calories CHO). Oral-glucose tolerance tests (oral-GTT) were performed pre-exercise and after 1, 3 and 6 days of Cr and placebo supplementation. Exercise depleted muscle glycogen content to the same extent in both treatment groups. Creatine supplementation increased muscle total-Cr, free-Cr and phosphocreatine (PCr) content above placebo following 1, 3 and 6 days of supplementation (all P < 0.05). Creatine supplementation also increased muscle glycogen content noticeably above placebo after 1 day of supplementation (P < 0.05), which was sustained thereafter. This study confirmed dietary Cr augments post-exercise muscle glycogen super-compensation, and demonstrates this occurred during the initial 24 h of post-exercise recovery (when muscle total-Cr had increased by <10 %). This marked response ensued without apparent treatment differences in muscle insulin sensitivity (oral-GTT, muscle GLUT4 mRNA), osmotic stress (muscle c-fos and HSP72 mRNA) or muscle cell volume (muscle water content) responses, such that another mechanism must be causative.
authors.affiliation: School of Biomedical Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, NG7 2UH, UK.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Roberts
authors.affiliation: School of Biomedical Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, NG7 2UH, UK.
authors.forename: John
authors.initials: J
authors.lastname: Fox
authors.affiliation: School of Biomedical Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, NG7 2UH, UK.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Peirce
authors.affiliation: School of Biomedical Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, NG7 2UH, UK.
authors.forename: Simon W
authors.initials: SW
authors.lastname: Jones
authors.affiliation: Human Metabolic Physiology and Nutrition, QinetiQ Centre for Human Sciences, Farnborough, UK.
authors.forename: Anna
authors.initials: A
authors.lastname: Casey
authors.affiliation: School of Biomedical Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, NG7 2UH, UK. paul.greenhaff@nottingham.ac.uk.|School of Life Sciences, The Medical School, Nottingham, NG7 2UH, UK. paul.greenhaff@nottingham.ac.uk.
authors.forename: Paul L
authors.initials: PL
authors.lastname: Greenhaff
mesh_terms: D000328:Adult; D003401:Creatine / Q000008:administration & dosage*; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D005786:Gene Expression Regulation / Q000187:drug effects; D005951:Glucose Tolerance Test; D006003:Glycogen / Q000378:metabolism*; D006801:Humans; D008297:Male; D009124:Muscle Proteins / Q000096:biosynthesis; D018482:Muscle, Skeletal / Q000378:metabolism*; D010807:Physical Endurance / Q000187:drug effects* / Q000502:physiology
chemical_list: D004040:Dietary Carbohydrates; D009124:Muscle Proteins; D006003:Glycogen; D003401:Creatine
keywords: Glucose tolerance; Glycogen storage; Insulin sensitivity; Phosphocreatine