Purpose: In the present study we investigated whether a high volume of cycling training would influence the metabolic changes associated with a succession of three exhaustive cycling exercises.
Methods: Seven professional road cyclists (V˙O2max: 74.3 ± 3.7 mL·min−1·kg−1; maximal power tolerated: 475 ± 18 W; training: 22 ± 3 h·wk−1) and seven sport sciences students (V˙O2max: 54.2 ± 5.3 mL·min−1·kg−1; maximal power tolerated: 341 ± 26 W; training: 6 ± 2 h·wk−1) performed three different exhaustive cycling exercise bouts (progressive, constant load, and sprint) on an electrically braked cycloergometer positioned near the magnetic resonance scanner. Less than 45 s after the completion of each exercise bout, recovery kinetics of high-energy phosphorylated compounds and pH were measured using 31P-MR spectroscopy.
Results: Resting values for phosphomonoesters (PME) and phosphodiesters (PDE) were significantly elevated in the cyclist group (PME/ATP: 0.82 ± 0.11 vs 0.58 ± 0.19; PDE/ATP: 0.27 ± 0.03 vs 0.21 ± 0.05). Phosphocreatine (PCr) consumption and inorganic phosphate (Pi) accumulation measured at end of exercise bouts 1 (PCr: 6.5 ± 3.2 vs 10.4 ± 1.6 mM; Pi: 1.6 ± 0.7 vs 6.8 ± 3.4 mM) and 3 (PCr: 5.6 ± 2.4 vs 9.3 ± 3.9 mM; Pi: 1.5 ± 0.5 vs 7.7 ± 3.3 mM) were reduced in cyclists compared with controls. During the recovery period after each exercise bout, the pH-recovery rate was larger in professional road cyclists, whereas the PCr-recovery kinetics were significantly faster for cyclists only for bout 3.
Discussion: Whereas the PDE and PME elevation at rest in professional cyclists may indicate fiber-type changes and an imbalance between glycogenolytic and glycolytic activity, the lower PCr consumption during exercise and the faster pH-recovery kinetic clearly suggest an improved mitochondrial function.
1University of Nantes, Nantes Atlantic Universities, Laboratory of Motricity, Interactions, and Performance, Nantes, FRANCE; and 2Department of Sport Physiology and 3Centre of Biological and Medical Magnetic Resonance, University of Aix-Marseille II, Marseille, FRANCE
Address for correspondence: François Hug, Ph.D., University of Nantes, Nantes Atlantic Universities, Laboratory of Motricity, Interactions, Performance, JE 2438, 25 bis boulevard Guy Mollet, BP 72206, Nantes, F-44000 France; E-mail: firstname.lastname@example.org.
Submitted for publication March 2006.
Accepted for publication June 2006.