title: Effect of intensified training on muscle ion kinetics, fatigue development, and repeated short-term performance in endurance-trained cyclists.
abstract: The effects of intensified training in combination with a reduced training volume on muscle ion kinetics, transporters, and work capacity were examined. Eight well-trained cyclists replaced their regular training with speed-endurance training (12 × 30 s sprints) 2-3 times per week and aerobic high-intensity training (4-5 × 3-4 min at 90-100% of maximal heart rate) 1-2 times per week for 7 wk and reduced training volume by 70% (intervention period; IP). The duration of an intense exhaustive cycling bout (EX2; 368 ± 6 W), performed 2.5 min after a 2-min intense cycle bout (EX1), was longer (P < 0.05) after than before IP (4:16 ± 0:34 vs. 3:37 ± 0:28 min:s), and mean and peak power during a repeated sprint test improved (P < 0.05) by 4% and 3%, respectively. Femoral venous K(+) concentration in recovery from EX1 and EX2 was lowered (P < 0.05) after compared with before IP, whereas muscle interstitial K(+) concentration and net muscle K(+) release during exercise was unaltered. No changes in muscle lactate and H(+) release during and after EX1 and EX2 were observed, but the in vivo buffer capacity was higher (P < 0.05) after IP. Expression of the ATP-sensitive K(+) (KATP) channel (Kir6.2) decreased by IP, with no change in the strong inward rectifying K(+) channel (Kir2.1), muscle Na(+)-K(+) pump subunits, monocarboxylate transporters 1 and 4 (MCT1 and MCT4), and Na(+)/H(+) exchanger 1 (NHE1). In conclusion, 7 wk of intensified training with a reduced training volume improved performance during repeated intense exercise, which was associated with a greater muscle reuptake of K(+) and muscle buffer capacity but not with the amount of muscle ion transporters.
authors.affiliation: Department of Exercise and Sport Sciences, Section of Human Physiology, University of Copenhagen, Denmark.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Gunnarsson
authors.forename: Peter M
authors.initials: PM
authors.lastname: Christensen
authors.forename: Martin
authors.initials: M
authors.lastname: Thomassen
authors.forename: Lars R
authors.initials: LR
authors.lastname: Nielsen
authors.forename: Jens
authors.initials: J
authors.lastname: Bangsbo
mesh_terms: D001642:Bicycling; D027682:Cation Transport Proteins / Q000378:metabolism; D004734:Energy Metabolism; D005080:Exercise Test; D006339:Heart Rate; D006801:Humans; D006863:Hydrogen-Ion Concentration; D017136:Ion Transport; D007700:Kinetics; D019344:Lactic Acid / Q000378:metabolism; D027501:Monocarboxylic Acid Transporters / Q000378:metabolism; D009119:Muscle Contraction; D018763:Muscle Fatigue; D009124:Muscle Proteins / Q000378:metabolism; D053580:Muscle Strength; D010101:Oxygen Consumption; D010807:Physical Endurance; D011188:Potassium / Q000378:metabolism*; D024661:Potassium Channels, Inwardly Rectifying / Q000378:metabolism; D052097:Quadriceps Muscle / Q000378:metabolism*; D020127:Recovery of Function; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism; D027981:Symporters / Q000378:metabolism; D000099233:Monocarboxylate Transport Protein 1; D000099161:Kcnj11 Channel
chemical_list: D027682:Cation Transport Proteins; D019344:Lactic Acid; D027501:Monocarboxylic Acid Transporters; D009124:Muscle Proteins; D011188:Potassium; D024661:Potassium Channels, Inwardly Rectifying; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers; D027981:Symporters; D000099233:Monocarboxylate Transport Protein 1; D000099161:Kcnj11 Channel; C489457:KCNJ2 protein, human; C406962:SLC16A4 protein, human; C490998:SLC9A1 protein, human
keywords: interstitial potassium and high-intensity training; lactate and proton release; potassium