Effect of Inhaled Molecular Hydrogen on Recovery Process After Downhill Walking on the Treadmill

The level of creatine kinase is measured from a venous blood sample taken by a healthcare specialist. Samples are collected in 2.7 ml citrate vacuum tubes. Samples are immediately centrifuged at 1000 g for 15 min and then divided into 0.5 ml cryotubes and frozen at -80 °C. Samples are taken pre-exercise (baseline), post-exercise, and 2 h, 24 h and 48 h post-exercise. Creatine kinase is determined by ELISA method according to the manufacturer's instructions.

A visual analogue scale is used to subjectively assess lower limb muscle soreness. The visual analogue scale is represented by a 100 mm line marked 0 - no pain and 100 - worst imaginable pain. The subject is instructed to mark a point on the line corresponding to their perceived muscle soreness. Muscle soreness is assessed pre-exercise (baseline), post-exercise, and 2 h, 24 h and 48 h post-exercise.

Reactive strength index is determined in 5 maximum hop test on AMTI OR6-7-1000 force platform (Advanced Mechanical Technology, Watertown, USA). Each subject is instructed to maximize the jump height and minimize the ground contact time. Reactive strength index is measured pre-exercise (baseline), post-exercise, and 2 h, 24 h and 48 h post-exercise.

The level of malondialdehydes is measured from a venous blood sample taken by a healthcare specialist. Samples are collected in 2.7 ml citrate vacuum tubes. Samples are immediately centrifuged at 1000 g for 15 min and then divided into 0.5 ml cryotubes and frozen at -80 °C. Samples are taken pre-exercise (baseline), post-exercise, and 2 h post-exercise. Malondialdehydes are determined using TBARS assay kit according to the manufacturer's instructions.

The level of Interleukin-6 is measured from a venous blood sample taken by a healthcare specialist. Samples are collected in 2.7 ml citrate vacuum tubes. Samples are immediately centrifuged at 1000 g for 15 min and then divided into 0.5 ml cryotubes and frozen at -80 °C. Samples are taken pre-exercise (baseline), post-exercise, and 2 h post-exercise. Interleukin-6 is determined by ELISA method according to the manufacturer's instructions.

Heart rate during the 90 min exercise is continuously recorded by Polar V800 heart rate monitor (Polar, Kempele, Finland).

Ventilation (air flow into and out of the lungs expressed in L/min) is measured with Ergostik analyser (Geratherm Respiratory, Bad Kissinger, Germany) breath by breath during the exercise and averaged over 5 min windows for subsequent analysis.

Oxygen uptake is measured with Ergostik analyser (Geratherm Respiratory, Bad Kissinger, Germany) breath by breath during the exercise and averaged over 5 min windows for subsequent analysis.

The level of blood lactate is measured from the fingertip blood sample using Lactate Scout+ analyser (EKF Diagnostics, Cardiff, UK) pre-exercise (baseline) and at specified time points (30, 60, and 90 min) during the exercise.

Subjects are asked to subjectively rate their perceived exertion at specified time points (30, 60, and 90 min) during the exercise. The Borg's scale 6 (no exertion at all) and 20 (maximal exertion) is used.