Metamax 3b

Minute ventilation ( ${\dot{\text{V}}}_{\text{E}}$ ), oxygen uptake ( $\dot{\text{V}}{\text{O}}_{\mathrm{2}}$ ), and carbon dioxide production ( $\dot{\text{V}}\text{C}{\text{O}}_{\mathrm{2}}$ ) were measured during the climbing and treadmill tests by a portable breath-by-breath indirect calorimetry system (MetaMax 3B, Cortex Biophysic, Germany). The MetaMax 3B was secured onto the chest by a harness. Before each test, gas and volume calibration was performed according to manufacturer's guidelines. The volume calibration was performed using a known 3L syringe and gas calibration was performed with a known gas mixture of 15% O₂ and 5% CO₂. Data was averaged over 20 s intervals; the mean of the last minute from submaximal climbing and the highest values from the maximal test were taken into analysis. RER was computed by dividing measured CO₂ by measured O₂. HR was monitored by the MetaMax 3B using a polar heart transmitter belt (Polar Electro OY, Finland). Heart rate maximum (HR_max⁡) was defined as the highest value attained during the test (recorded from 20 s averaged data).

Perceived exertion was assessed on a scale from 6 to 20 as suggested by Borg (1982) (link). Immediately after the test, climbers were shown a table with numbers and corresponding verbal description of the exertion and indicated their exertion rating to the researcher.
Physiological responses were assessed using a breath-by-breath portable metabolic system (MetaMax 3B, Cortex Biophysik, Germany). The device was worn by climbers on the chest with a harness (total weight 1.4 kg). Gas calibration was performed using a reference gas (15% O₂ and 5% CO₂), and volume calibration was performed using a 3-L syringe. Breath-by-breath data were averaged at 20-s intervals and exported to Excel for further analysis.
Oxygen uptake (VO₂), carbon dioxide production (VCO₂), expiratory ventilation (V_E), and breath frequency (BF) were measured by MetaMax 3B. Respiratory exchange ratio (RER) was computed by dividing VCO₂ by VO₂. EPOC was calculated from 10 min of sitting rest as total recovery VO₂ minus resting VO₂. The net climbing energy cost (EC) was computed from net climbing VO₂ and EPOC using the energy equivalent for oxygen of 4.924 kcal. The chest belt (Polar Electro OY, Finland) was used for monitoring the HR, which was transmitted automatically to the MetaMax 3B.