Heraeus primo r

Venous blood samples were dispensed into 2 × 5 mL EDTA-treated tubes (Sarstedt, Leicester, UK). The first of these tubes was immediately analysed for haemoglobin concentrations (Sysmex SF-3000 Sysmex Ltd., Wymbush, UK) and haematocrit ratio (Hawksley, Lancing, UK). Mean corpuscular haemoglobin concentration was calculated by dividing haemoglobin concentration by haematocrit ratio. The remaining EDTA-treated blood was then centrifuged at 2000 × g for 10 min at 4 °C (Heraeus Primo R; Thermo Fisher Scientific, Loughborough, UK) for plasma extraction, then stored at − 80 °C for later analysis of plasma albumin concentration using an automated spectrophotometric analyser (RX Daytona, Randox, Crumlin, Ireland).

A 4-ml blood sample (VACUETTE® Z Serum Clot Activator) was collected via aseptic venipuncture at the same time of the day for each participant from the antecubital vein while resting in a seated position for the determination of resting serum BDNF levels pre- and post-training. Participants were not required to fast before each blood collection. The blood was allowed to clot for at least 30 min at room temperature and was then centrifuged (Heraeus™ Primo™ R, Thermo Fisher, Waltham, MA) for 10 min at 2200 relative centrifugal force at 20°C. The supernatant was decanted and stored in a -80°C freezer until assayed. Serum concentrations of BDNF were measured using a MILLIPLEX kit (Human Pituitary Bead Panel 2, EMD Millipore, Billerica, MA) according to the manufacturer’s instructions. Samples and BDNF standards were measured in duplicate and results reported in this study were obtained with a sample dilution of 1 part serum to 10 parts sample diluent. The 96-well plate was incubated overnight with agitation on a plate shaker (ThermoMixer® C, Eppendorf, Hamburg, Germany) at 700 rpm and 4°C and the plate was run using MAGPIX® with xPONENT software (Luminex, Austin, TX). The sensitivity as reported in the MILLIPLEX kit literature was 2.45 pg/ml with an intraassay and interassay CV of <10 and <15%, respectively.