Metabolic and neuromuscular adaptations to endurance training in professional cyclists: A longitudinal study

The aim of this longitudinal study was to analyze the changes in several me tabolic and neuromuscular variables in response to endurance training durin g three defined periods of a full sports season (rest, precompetition and c ompetition). The study population was formed by thirteen professional cycli sts (age+/-SEM: 24+/-1 years; mean (V) over dot O-2 (max) similar to 74 ml. kg(-1).min(-1)). In each testing session, subjects performed a ramp test un til exhaustion on a cycle ergometer (workload increases of 25 W.min(-1)). T he following variables were recorded every 100 W until the tests: oxygen co nsumption ((V) over dot O-2, in l.min(-1)), respiratory exchange ratio (RER in (V) over dot CO2.(V) over dot O-2(-1)) and blood lactate, pH and bicarb onate concentration [HCO3-]. Surface electromyography (EMG) recordings were also obtained from the vastus lateralis to determine the variables: root m ean square voltage (rms-EMG) and mean power frequency (MPF), RER and lactat e values both showed a decrease (p <0.05) throughout the season at exercise intensities corresponding to submaximal workloads. In contrast, no signifi cant differences were found in mean pH or [HCO3-]. Finally, rms-EMG tended to increase during the season, with significant differences (p<0.05) observ ed mainly between the competition and rest periods at most workloads. In co ntrast, precompetition MPF values increased (p<0.05) with respect to restin g values at most submaximal workloads but fell (p<0.05) during the competit ion period. Our findings suggest that endurance conditioning induces the fo llowing general adaptations in elite athletes: (1) lower circulating lactat e and increased reliance on aerobic metabolism at a given submaximal intens ity, and possibly (2) an enhanced recruitment of motor units in active musc les, as suggested by rms-EMG data.