The purpose of the study was to investigate the effects of implementing additional respiratory dead space during cycloergometry-based aerobic training. The primary outcome measures were respiratory exchange ratio (RER) and carbon dioxide production (VCO₂). Two groups of young healthy males: Experimental (Exp, n = 15) and Control (Con, n = 15), participated in this study. The training consisted of 12 sessions, performed twice a week for 6 weeks. A single training session consisted of continuous, constant-rate exercise on a cycle ergometer at 60% of VO₂max which was maintained for 30 minutes. Subjects in Exp group were breathing through additional respiratory dead space (1200ml), while subjects in Con group were breathing without additional dead space. Pre-test and two post-training incremental exercise tests were performed for the detection of gas exchange variables. In all training sessions, pCO₂ was higher and blood pH was lower in the Exp group (p < 0.001) ensuring respiratory acidosis. A 12-session training program resulted in significant increase in performance time in both groups (from 17”29 ± 1”31 to 18”47 ± 1”37 in Exp; p=0.02 and from 17”20 ± 1”18 to 18”45 ± 1”44 in Con; p = 0.02), but has not revealed a significant difference in RER and VCO₂ in both post-training tests, performed at rest and during submaximal workload. We interpret the lack of difference in post-training values of RER and VCO₂ between groups as an absence of inhibition in glycolysis and glycogenolysis during exercise with additional dead space.

• The purpose of the study was to investigate the effects of implementing additional respiratory dead space during cycloergometry-based aerobic training on respiratory exchange ratio and carbon dioxide production.

• In all training sessions, respiratory acidosis was gained by experimental group only.

• No significant difference in RER and VCO between experimental and control group due to the trainings.

• The lack of difference in post-training values of RER and VCO between groups means absence of inhibition in glycolysis and glycogenolysis during exercise with additional dead space.