The filtrate was collected systematically for analysis using a gas chromatograph GC-2014 (Shimadzu) equipped with a DB-wax 123-7033 (Agilent) capillary column (0.32 mm i.d., 30 m long) and a flame ionization detector (FID).
The gas analysis system was calibrated using a gas mixture of known O2 and CO2 concentrations before each test.
Compound specific isotope analysis (CSIA), using a gas chromatograph (GC) combustion interfaced isotope ratio mass spectrometry (GC-C-IRMS), provides isotopic characterization of individual compounds and thereby enabling the assessment of the degradation processes in a quantitative way.
The volatile analysis was performed using a gas chromatograph/mass spectrometer (GC/MS) equipped with an olfactory detector.
The analysis was performed using a gas chromatograph provided with capillary column (DB-5, J&W Scientific, USA).
GC analysis was performed using a gas chromatograph (7890N; Agilent Technologies), equipped with an FID and split/splitless injector system.
Produced gas was sampled from one of the sampling loop ports using a gas-tight syringe for gas analysis injection.
Oxygen consumption was measured using a portable gas analysis system (Oxycon Mobile, Jaeger, Hoechberg, Germany).
On a separate occasion, subjects performed an exhaustive incremental cycling test (Lode Excalibur Sport, Groningen, the Netherlands) to determine maximal power output (Wmax) and maximal oxygen uptake capacity (VO2peak) using an online gas analysis system (SensorMedics, Bilthoven, the Netherlands).
