In this episode, Simon and Brian discuss their experiences with high altitude breath work training. They start by explaining the breath assessments used to determine dysfunctional breathing and carbon dioxide tolerance. They then discuss the importance of controlling the exhale during the carbon dioxide tolerance test and the role of CO2 in breathlessness. They also touch on the effects of altitude on the test results. The conversation then moves on to the practice of hyperventilation and its impact on breath-holding ability. Finally, they demonstrate the 'breathe light' exercise to train the chemoreceptors in the brainstem to tolerate higher levels of CO2. The conversation focused on the experiences and takeaways from the five-week breathwork training program. Both participants mentioned the challenge of finding time for the exercises but acknowledged the progress they saw in their breath assessment scores. They also discussed the potential benefits of the training in improving performance at altitude. While it was difficult to determine the exact impact of the breathing exercises, they felt that it had a positive effect on their ability to control their breath and stay in lower heart rate zones during physical activities. Overall, they found value in incorporating breathwork into their training routines.