Breathing valve resistance alters physiological responses during a graded exercise test

Purpose To determine the impact of breathing valve resistance on peak aerobic capacity ( V ˙ O 2 peak ) and running economy (RE) in endurance-trained and recreationally active individuals. Methods Ten endurance-trained males (ETM), 10 endurance-trained females (ETF), 10 recreationally active males (RAM), and 10 recreationally active females (RAF) participated in this study. On two separate occasions, subjects performed identical graded exercise treadmill protocols using either a Hans Rudolph 2700 (high resistance) or a Daniels’ (low resistance) two-way non-rebreathing valve. Parameters obtained from these protocols included energy expenditure (EE), ventilation ( V ˙ E ), heart rate, respiratory exchange ratio, RE, V ˙ O 2 peak , and time to exhaustion (TTE). Results When using the Daniels’ valve, all groups had lower submaximal EE (− 2.4, − 3.4, − 2.7, and − 2.0% for ETM, ETF, RAM, and RAF) and better RE (− 2.7, − 3.5, − 1.9, and − 1.8% for ETM, ETF, RAM and RAF) across all submaximal speeds. Only the ET groups had lower submaximal V ˙ E (4.6 and 3.8% for ETM and ETF) when using the Daniels’ valve. TTE increased when using the Daniels’ valve for all groups (6.0, 10.9, 6.2 and 9.8% for ETM, ETF, RAM and RAF), but V ˙ O 2 peak was unaltered. Conclusion Compared to the Daniels’ valve, the Hans Rudolph 2700 valve altered the assessment of RE, submaximal EE, and TTE regardless of fitness level or sex, but did not change V ˙ O 2 peak . Therefore, airflow resistance of a breathing valve must be considered when assessing and comparing EE, RE and TTE in the applied and research settings.